# Patent

## Title
Method for producing ultra-heat treatment milk

## Abstract

The invention relates to using a lipid acyltransferase polypeptide (SEQ ID NO: 68) in the manufacture of ultra-heat treatment milk (UHT) for improving the stability, the perceptible sensory difference, the smell, and the taste; and for reducing the cholesterol content, and for eliminating or reducing creaming of the UHT milk. The invention also relates to a method of producing UHT milk, wherein the method comprises admixing a lipid acyltransferase with milk and heating the mixture to make it a UHT milk.

## Background
INCORPORATION BY REFERENCE
This application is a continuation-in-part application of international patent application Serial No. PCT/IB2008/002573 filed Aug. 14, 2008, which published as PCT Publication No. WO 2009/024862 on Feb. 26, 2009, which claims benefit of European patent application Serial No. GB0716126.8 filed Aug. 17, 2007.
Reference is made to the following related applications: US 2002-0009518, US 2004-0091574, WO2004/064537, WO2004/064987, WO2005/066347, WO2005/066351, U.S. Application Ser. No. 60/764,430 filed on 2 Feb. 2006, WO2006/008508, International Patent Application Number PCT/IB2007/000558 and U.S. application Ser. No. 11/671,953.
The foregoing applications, and all documents cited therein or during their prosecution (“appln cited documents”) and all documents cited or referenced in the appln cited documents, and all documents cited or referenced herein (“herein cited documents”), and all documents cited or referenced in herein cited documents, together with any manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated by reference herein, are hereby incorporated herein by reference, and may be employed in the practice of the invention.


SEQUENCE LISTING
The instant application contains a Sequence Listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on May 16, 2013 is named 43049.00.2092_SL.txt and is 194,613 bytes in size.
FIELD OF THE PRESENT INVENTION
The present invention relates to a process for the manufacture of UHT milk, a process for enzymatic treatment of UHT milk, an enzymatically treated UHT milk and uses of an enzyme for the treatment of UHT milk to provide new and unexpected technical advantages.
BACKGROUND OF THE PRESENT INVENTION
Lipid acyltransferases are known to be advantageous in food applications. Lipid acyltransferases have been found to have significant acyltransferase activity in foodstuffs. This activity has surprising beneficial applications in methods of preparing foodstuffs.
For instance, WO 2004/064537 pertains to a method for the in situ production of an emulsifier by use of a lipid acyltransferase and the advantages associated therewith.
International Patent Application No. PCT/IB2001/000558 relates to the expression of lipid acyltransferases in (heterologous) host cell and is incorporated herein by reference.
Heat treatment in the production of long-life products is often called “sterilisation”. This means that the product is exposed to such powerful heat treatment that all relevant microorganisms and most of the heat resistant enzymes are inactivated. Such products have excellent keeping qualities and can be stored for long periods of time at ambient temperatures. Many dairies can therefore distribute these products over long distances and thereby find new markets.
Typically two methods are used for the production of sterilised (otherwise known as long-life milk for ambient storage), namely in-container sterilisation or UHT treatment followed by aseptic packaging in packages protecting the product against light and atmospheric oxygen. The present invention is applicable to long-life milk produced by any method, e.g. UHT milk.
There are many advantages for the producer, retailer and consumer if the product does not require refrigeration and can be stored for long periods without spoiling.
These products are often called UHT-products, particularly UHT milk or UHT flavoured milks.
Milk exposed to UHT treatment must be of a very good quality. It is particularly important that the proteins in the raw milk do not cause thermal instability, which can be the case if the raw milk is of bad quality. A milk is unsuitable for UHT treatment if it is sour, has the wrong salt balance and/or contains too many serum proteins, typical of colostrum.
When milk is kept at a high temperature for a long time, certain chemical reaction products are formed, which results in discolouration (browning). It also acquires a cooked and caramel flavour, and there is occasionally a great deal of sedimentation. These defects are largely avoided by heat treatment at a higher temperature for a short time. It is important that the optimum time/temperature combination is chosen to enable satisfactory spore destruction while keeping heat damage to the milk to a minimum.
It has been shown that when milk is heated (e.g. pasteurised at 70-80° C. for 5-20 seconds), an effect known as the “cream plug phenomenon” is evident. Heat treatment of milk may be detrimental to the stability of the milk.
The principal constituents of milk are water, fat, proteins, lactose (milk sugar) and minerals (salts). Milk also contains smaller amounts of other substances such as pigments, enzymes, vitamins, phospholipids (substances with fat like properties), sterols and gases.
The many lipids of milk, together forming the ‘milk fat’, have a very complicated composition and structure, even more complicated than most other naturally occurring fats. Typically milk fat consists of triglycerides, di- and monoglycerides, fatty acids, sterols, carotenoids and vitamins (A, D, E and K). Other components include phospholipids, lipoproteins, glycerides, cerebrosides, proteins, nucleic acids, enzymes, metals and water.
Phospholipids are the most surface-active class, as they are amphipolar. As the molecular size is relatively large, they are hardly soluble, neither in water nor in fat. In both liquids they tend to form lamellar bilayers. Phospholipids of milk are generally seen in close connection with proteins, especially when located in the membrane(s) of milk fat globules. The main part of phospholipids in milk is Lecithins, which are surface active at moderate hydrophilicity. Thus lecithin can be seen as a suspending and dispersing agent or as an emulsifier for O/W emulsions as well as for W/O emulsions.
Phospholipids comprises 0.8-1.0% of the natural milk fat. The main types of phospholipids/lecithin in milk are phosphatidylcholine and phosphatidylethanolamine.
Sterols are highly insoluble in water, and show very little surface activity. They easily associate with phospholipids. The cholesterol may be considered an unwanted ingredient in milk when considering the nutritional value of milk. Cholesterol comprises 0.3-0.4% of the natural milk fat.
EP 1 532 863 relates to the use of a phospholipase to treat a cheese milk or a cheese milk fraction.
Tanji et al (Res. Bull. Obihiro Univ., 22 (2001): 89-94) relates to the use of lipases to enhance flavour in butter oil at 40° C.
JP 57-189637 and JP57-189638 pertains to the treatment of milk to produce fermented or acidic milk drinks using phospholipases—where the enzymatic treatment is done at 30-45° C.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.
SUMMARY OF THE INVENTION
Aspects of the present invention are presented in the claims and in the following commentary.
It has surprisingly been found that the stability, particularly the long term stability, of UHT milk can be significantly improved by exposing milk or a portion thereof during UHT milk production to a lipid acyltransferase as defined herein.
Even more surprisingly the inventors of the present invention have found that the enzymatic treatment can be carried out without an additional heating step. Hence the adverse effects of heating the milk twice, i.e. once for enzymatic treatment and then again for the UHT treatment can be avoided. This has many advantages as described below.
It is noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the invention.
These and other embodiments are disclosed or are obvious from and encompassed by, the following Detailed Description.
DETAILED DESCRIPTION
According to a first aspect of the present invention there is provided a method of producing UHT milk, wherein said method comprises admixing a lipid acyltransferase and milk or a fraction thereof; and treating the enzyme treated milk by ultra-heat treatment to produce UHT milk.
“Ultra-heat treatment (UHT)” is a process where the milk is heated to approximately 130-150° C. and held there for a few seconds, such as one to three seconds, preferably two seconds. The terms “ultra-heat treatment” and “ultra-high temperature treatment” and “high temperature treatment” are used synonymously herein.
In one embodiment, the term “ultra-heat treatment” as used herein is meant to encompass both in-container sterilisation and/or UHT treatment followed by aseptic packaging in packages protecting the product against light and atmospheric oxygen.
As one skilled in the art will appreciate, the UHT heat treatment time and temperature combination will be established based upon the product to be treated and may vary to some degree.
The UHT milk after heat treatment may be sent to a Sterile tank to give a buffer prior to filling.
Filling is usually done in a sterile atmosphere where the UHT packing machine flushes the package with Nitrogen and also keeps the area within the filling heads flooded with Nitrogen to eliminate any air contamination.
According to a second aspect of the present invention there is provided a use of a lipid acyltransferase in the manufacture of UHT milk for improving the stability, particularly the long term stability, of the UHT milk.
The term “improving the stability” as used herein means that there is a reduction in the amount of creaming and/or sedimentation and/or flocculation and/or phase separation following storage (preferably following storage for at least 24 hours). Suitably the storage may be at a temperature of between about 5° C. and 35° C.
In one embodiment, the term “improving the stability” as used herein means that there is a reduction in the amount of creaming without formation of a sediment layer following storage (preferably following storage for at least 24 hours). Suitably the storage may be at a temperature of between about 5° C. and 35° C.
Creaming may be measured objectively by Turbiscan (as taught herein in the Examples section) and/or subjectively by the Stress Test (as taught herein in the Examples section).
Flocculation may be measured objectively by Turbiscan (as taught herein in the Examples section) and/or subjectively by the Stress Test (as taught herein in the Examples section).
Sedimentation may be measured by the Sedimentation Test (as taught herein in the Examples section).
Phase separation may be measured visually or by Turbiscan (as taught herein in the Examples section).
The term “improving the long term stability” as used herein means that there is a reduction in the amount of creaming (preferably without formation of a sediment layer) and/or sedimentation and/or flocculation and/or phase separation following storage over a prolonged period of time (preferably following storage for about 1-12 months, more preferably following storage for about 3-12 months, preferably following storage for up to about 6 months, preferably following storage for up to about 12 months, more preferably following storage for at least about 6 months). Suitably the storage may be at a temperature between about 5° C. and 35° C.
According to a third aspect of the present invention there is provided a use of a lipid acyltransferase in the manufacture of UHT milk for improving the perceptible sensory difference of the UHT milk. Suitably the perceptible sensory difference of the UHT milk may be measured using the “triangle test” taught herein under.
In one aspect the “perceptible sensory difference” includes improved smell and/or taste, for example a reduced cooked taste and/or aroma and/or a reduced rancidity taste and/or aroma.
According to a fourth aspect of the present invention there is provided a use of a lipid acyltransferase in the manufacture of UHT milk for reducing the cholesterol content in the UHT milk.
A reduction in cholesterol can be measured by Thin Layer Chromatography (TLC) and/or Gas Liquid Chromatography (GLC).
According to a fifth aspect of the present invention there is provided a use of a lipid acyltransferase in the manufacture of UHT milk for eliminating or reducing creaming (preferably without formation of a sediment layer) in the UHT milk.
Suitably the improvement in the stability, particularly the long term stability, and/or the improvement in the perceptible sensory difference and/or the improvement in smell and/or taste and/or the reduction in cholesterol content and/or reduction in creaming (preferably without formation of a sediment layer) of the UHT milk means an improvement when the enzymatically treated UHT milk (treated with enzymes in accordance with the present invention) is compared with UHT milk which has not been enzymatically treated and/or compared with UHT milk which has been treated with a phospholipase (in particular either a phospholipase A1 enzyme classified as E.C. 3.1.1.32 or a phospholipase A2 enzyme classified as EC.3.1.1.4).
Suitably the improvement in the stability, particularly the long term stability, and/or the improvement in the perceptible sensory difference and/or the improvement in smell and/or taste and/or the reduction in cholesterol content and/or reduction in creaming (preferably without formation of a sediment layer) of the UHT milk may mean an improvement when the enzymatically treated UHT milk (treated with enzymes in accordance with the present invention) is compared with UHT milk which has been treated with one or more of the following phospholipases: Phospholipase A1 from Fusarium oxysporum (Lipopan FTM) and/or a phospholipase from Fusarium heterosporum and/or a phospholipase A1 from Fusarium venenatum (YieldMaxTM) and/or a phospholipase from Aspergillus niger and/or a phospholipase A2 from Streptomyces violaceoruber and/or a phospholipase A2 from porcine pancreas and/or a phospholipase A2 from Tuber borchii. 
Suitably the improvement in the stability, particularly the long term stability, and/or the improvement in the perceptible sensory difference and/or the improvement in smell and/or taste and/or the reduction in cholesterol content and/or reduction in creaming (preferably without formation of a sediment layer) of the UHT milk may mean an improvement when the enzymatically treated UHT milk is compared with UHT milk which has been treated with a phospholipase A1 from Fusarium oxysporum (Lipopan FTM).
Preferably it is advantageous to admix the lipid acyltransferase with the milk or a portion thereof before it is undergoes high temperature treatment. In other words the lipid acyltransferase may be added to raw milk or a portion thereof, and the enzyme-treated raw milk or portion thereof then undergoes ultra-heat treatment (resulting in UHT milk or a portion thereof).
In one embodiment of the present invention, the present invention may provide a method of producing UHT milk, wherein said method comprises comprising admixing a lipid acyltransferase and UHT milk or a fraction thereof. Suitably, in some embodiments the lipid acyltransferase may be added to the milk or a portion thereof after the ultra-heat treatment of the milk.
Preferably the lipid acyltransferase is added to the milk and incubated therewith at a temperature of less than about 20° C., preferably less than about 10° C.
Preferably the lipid acyltransferase is added to the milk and incubated therewith at a temperature of between about 1° C. and about 10° C., preferably between about 3° C. and about 7° C., more preferably about 5° C.
Preferably the incubation time is effective to ensure that there is at least 5% transferase activity, preferably at least 10% transferase activity, preferably at least 15%, 20%, 25% 26%, 28%, 30%, 40% 50%, 60% or 75% transferase activity.
The transferase activity is measured by the molar amount of cholesterol ester formed by acyltransfer from phospholipids or triacylglycerides in milk to cholesterol relative to the amount of cholesterol originally available

Transferase activity=(Mol/l cholesterol ester(t)−Mol/l cholesterol ester(0))×100 Mol/l cholesterol(0)

Where:

Cholesterol ester(t)=the amount of cholesterol ester to the time t

Cholesterol ester(0)=the amount of cholesterol ester to the time 0

Cholesterol (0)=the amount of cholesterol in milk to the time 0

Cholesterol and cholesterol ester are determined by GLC

Gas Chromatography:

Gas Chromatography is used to measure the content of cholesterol and cholesterol-ester in the milk samples.

The following CG setup is used:

Perkin Elmer Autosystem 9000 Capillary Gas Chromatograph equipped with WCOT fused silica column 12.5 m×0.25 mm ID×0.1μ film thickness 5% phenyl-methyl-silicone (CP Sil 8 CB from Chrompack).

Carrier gas: Helium.

Injector. PSSI cold split injection (initial temp 50° C. heated to 385° C.), volume 1.0 μl

Detector FID: 395° C.













Oven program



(used since



30.10.2003):











1
2
3















Oven temperature, ° C.
90
280
350



Isohtermal, time, min.
1
0
10



Temperature rate, ° C./min.
15
4









Preparation of Milk Samples for Gc Analysis:

The milk lipids are extracted according to Mojonnier AOAC 989.05 using ethanol, NH3, MTBE (methyl-tert-butyl ether) and p-ether. The lipid fraction is redissolved in heptane/pyridine (2:1) containing heptadecan as internal standard and cholesterol is measured by GC.
Preparing samples for cholesterol-ester measurements Squalane is added as an additional internal standard. The lipid fraction is redissolved in hexane and cholesterol-esters are concentrated using a NH2 Bond Elut column and hexane eluation. Samples are redissolved in heptane/pyridine (2:1) and cholesterol-esters are measured by CG.
Preferably the combination of temperature and the incubation time is effective to ensure that there is at least 5% transferase activity, preferably at least 10% transferase activity, preferably at least 15%, 20%, 25% 26%, 28%, 30%, 40% 50%, 60% or 75% transferase activity.
Suitably the incubation time may be from 5 minutes up to 30 hours, suitably the incubation time may be from 45 minutes up to 30 hours.
In one embodiment the incubation time may be from about 10 hours to about 30 h, preferably from about 15 to 25 hours, more preferably about 20 hours.
In a preferred embodiment the enzymatic treatment takes place at about 3° C. to about 10° C. (preferably about 5° C.) for at least 10 hours, preferably between about 10 and 25 hours, more preferably about 20 hours.
The use of lower temperatures in combination with effective incubation times leads to significant advantages in the present invention.
In the methods and/or uses of the present invention preferably the milk (UHT milk) is not heated during enzymatic treatment.
Preferably in the methods and/or uses of the present invention the milk is only heated once (when it is ultra-heat treated to provide a UHT milk). Therefore, preferably the milk (e.g. UHT milk) in the present invention does not undergo more than one heating step during it production.
In some aspects, the lipid acyltransferase for use in any one of the methods and/or uses of the present invention may comprise a GDSX (SEQ ID NO: 120) motif and/or a GANDY (SEQ ID NO: 118) motif. Preferably, the lipid acyltransferase enzyme is characterised as an enzyme which possesses acyltransferase activity and which comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S.
Suitably, the nucleotide sequence encoding a lipid acyltransferase or lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be obtainable, preferably obtained, from an organism from one or more of the following genera: Aeromonas, Streptomyces, Saccharomyces, Lactococcus, Mycobacterium, Streptococcus, Lactobacillus, Desulfitobacterium, Bacillus, Campylobacter, Vibrionaceae, Xylella, Sulfolobus, Aspergillus, Schizosaccharomyces, Listeria, Neisseria, Mesorhizobium, Ralstonia, Xanthomonas and Candida. Preferably, the lipid acyltransferase is obtainable, preferably obtained, from an organism from the genus Aeromonas. 
In some aspects of the present invention, the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention encodes a lipid acyltransferase that comprises an aspartic acid residue at a position corresponding to N-80 in the amino acid sequence of the Aeromonas hydrophila lipid acyltransferase shown as SEQ ID NO: 35.
In some aspects of the present invention, the lipid acyltransferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that comprises an aspartic acid residue at a position corresponding to N-80 in the amino acid sequence of the Aeromonas hydrophila lipid acyltransferase shown as SEQ ID NO: 35.
In addition or in the alternative, the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention encodes a lipid acyltransferase that may comprise the amino acid sequence shown as SEQ ID NO: 16, or an amino acid sequence which has 75% or more homology thereto. Suitably, the nucleotide sequence encoding a lipid acyltransferase encodes a lipid acyltransferase that may comprise the amino acid sequence shown as SEQ ID NO: 16.
In addition or in the alternative, the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention encodes a lipid acyltransferase that may comprise the amino acid sequence shown as SEQ ID NO: 68, or an amino acid sequence which has 75% or more homology thereto. Suitably, the nucleotide sequence encoding a lipid acyltransferase encodes a lipid acyltransferase that may comprise the amino acid sequence shown as SEQ ID NO: 68.
In one embodiment the lipid acyltransferase for use in any on of the methods and/or uses of the present invention has an amino acid sequence shown in SEQ ID NO: 16 or SEQ ID NO: 68, or has an amino acid sequence which has at least 75% identity therewith, preferably at least 80%, preferably at least 85%, preferably at least 95%, preferably at least 98% identity therewith.
The term “UHT milk” means herein any long-life milk designed for ambient storage. In particular “UHT milk” means any milk which has been heat-treated using to make it long-life milk, this includes flavoured and unflavoured products.
Suitably, the method may comprise a step of removing the enzyme and/or denaturing the enzyme.
Suitably the enzyme for use in the present invention may be an immobilised enzyme.
The milk product of the present invention is a UHT milk or a UHT flavoured milk.
It is not intended to cover herein cheese milk (i.e. a milk which is not a UHT milk and which is used in the subsequent preparation of cheese) and/or cheese or cheese products produced from a milk which is not UHT milk.
One advantage of the present invention is that the stability, particularly the long term stability, of UHT milk can be significantly improved.
A further advantage is that the unwanted physical effect of “creaming” of UHT milk is prevented and/or reduced compared with UHT milk which has not been enzymatically treated and/or compared with UHT milk which during its manufacture has been treated with a phospholipase (in particular either a phospholipase A1 enzyme classified as E.C. 3.1.1.32 or a phospholipase A2 enzyme classified as EC.3.1.1.4) (rather than the lipid acyltransferase as described herein).
The term “creaming” as used herein means the undesirable gravitational rise of fat globules to the top of the milk (e.g. in a container) over time.
A further advantage of the present invention may be the reduction of surface tension in UHT milk treated in accordance with the present invention compared with UHT milk which has not been enzymatically treated and/or compared with UHT milk which during its manufacture has been treated with a phospholipase (in particular either a phospholipase A1 enzyme classified as E.C. 3.1.1.32 or a phospholipase A2 enzyme classified as EC.3.1.1.4) (rather than the lipid acyltransferase as described herein).
A further advantage of the present invention may be the reduction of fouling of the UHT plant (e.g. of the plant tubes and/or steel surfaces) when using the UHT milk treated in accordance with the present invention compared with UHT milk which has not been enzymatically treated and/or compared with UHT milk which during its manufacture has been treated with a phospholipase (in particular either a phospholipase A1 enzyme classified as E.C. 3.1.1.32 or a phospholipase A2 enzyme classified as EC.3.1.1.4) (rather than the lipid acyltransferase as described herein).
A further advantage of the present invention may be a reduction in free fatty acids in UHT milk treated in accordance with the present invention compared with UHT milk which during its manufacture has been treated with a phospholipase (in particular either a phospholipase A1 enzyme classified as E.C. 3.1.1.32 or a phospholipase A2 enzyme classified as EC.3.1.1.4) (rather than the lipid acyltransferase as described herein).
Even more surprisingly the inventors of the present invention have found that the enzymatic treatment can be carried out without an additional heating step. In particular the enzymatic treatment using the lipid acyltransferase in accordance with the present invention may be carried out at temperatures as low as approximately 1-25° C., preferably as low as approximately 1-10° C., preferably between about 3 and about 7° C., more preferably about 5° C. Hence the adverse effects of heating the milk twice, i.e. once for the UHT treatment and then again for enzymatic treatment, can be avoided. This has many advantages including:

    
    
        a) that the process is more economic and is therefore advantageous for producers of the UHT milk;
        b) heating of the milk can lead to adverse effects such as a breakdown in stability of the constituents of the milk, the present invention reduces significantly this disadvantageous property; and/or
        c) less changes in organoleptic properties.
    
    


A further advantage of the present invention is a reduced cholesterol content in the UHT milk which may have major health benefits.
Suitably the improvement in any of the characteristics taught herein (such as creaming) may be compared with UHT milk which has been treated with one or more of the following phospholipases: Phospholipase A1 from Fusarium oxysporum (Lipopan FTM) and/or a phospholipase A1 from Fusarium venenatum (YieldMaxTM) and/or a phospholipase from Fusarium heterosporum and/or a phospholipase from Aspergillus niger and/or a phospholipase A2 from Streptomyces violaceoruber and/or a phospholipase A2 from porcine pancreas and/or a phospholipase A2 from Tuber borchii; preferably Phospholipase A1 from Fusarium oxysporum (Lipopan FTM).
Host Cell
The host organism can be a prokaryotic or a eukaryotic organism.
In one embodiment of the present invention the lipid acyl transferase according to the present invention in expressed in a host cell, for example a bacterial cells, such as a Bacillus spp, for example a Bacillus licheniformis host cell.
Alternative host cells may be fungi, yeasts or plants for example.
It has been found that the use of a Bacillus licheniformis host cell results in increased expression of a lipid acyltransferase when compared with other organisms, such as Bacillus subtilis. 
A lipid acyltransferase from Aeromonas salmonicida has been inserted into a number of conventional expression vectors, designed to be optimal for the expression in Bacillus subtilis, Hansenula polymorpha, Schizosaccharomyces pombe and Aspergillus tubigensis, respectively. Only very low levels were, however, detected in Hansenula polymorpha, Schizosaccharomyces pombe and Aspergillus tubigensis. The expression levels were below 1 μg/ml, and it was not possible to select cells which yielded enough protein to initiate a commercial production (results not shown). In contrast, Bacillus licheniformis was able to produce protein levels, which are attractive for an economically feasible production.
In particular, it has been found that expression in B. licheniformis is approximately 100-times greater than expression in B. subtilis under the control of aprE promoter or is approximately 100-times greater than expression in S. lividans under the control of an A4 promoter and fused to cellulose (results not shown herein).
The host cell may be any Bacillus cell other than B. subtilis. Preferably, said Bacillus host cell being from one of the following species: Bacillus licheniformis; B. alkalophilus; B. amyloliquefaciens; B. circulans; B. clausii; B. coagulans; B. firmus; B. lautus; B. lentus; B. megaterium; B. pumilus or B. stearothermophilus. 
The term “host cell”—in relation to the present invention includes any cell that comprises either a nucleotide sequence encoding a lipid acyltransferase as defined herein or an expression vector as defined herein and which is used in the recombinant production of a lipid acyltransferase having the specific properties as defined herein.
Suitably, the host cell may be a protease deficient or protease minus strain and/or an α-amylase deficient or α-amylase minus strain.
The term “heterologous” as used herein means a sequence derived from a separate genetic source or species. A heterologous sequence is a non-host sequence, a modified sequence, a sequence from a different host cell strain, or a homologous sequence from a different chromosomal location of the host cell.
A “homologous” sequence is a sequence that is found in the same genetic source or species i.e. it is naturally occurring in the relevant species of host cell.
The term “recombinant lipid acyltransferase” as used herein means that the lipid acyltransferase has been produced by means of genetic recombination. For instance, the nucleotide sequence encoding the lipid acyltansferase has been inserted into a cloning vector, resulting in a B. licheniformis cell characterised by the presence of the heterologous lipid acyltransferase.
Regulatory Sequences
In some applications, a lipid acyltransferase sequence for use in the methods and/or uses of the present invention may be obtained by operably linking a nucleotide sequence encoding same to a regulatory sequence which is capable of providing for the expression of the nucleotide sequence, such as by the chosen host cell (such as a B. licheniformis cell).
By way of example, a vector comprising the nucleotide sequence of the present invention operably linked to such a regulatory sequence, i.e. the vector is an expression vector, may be used.
The term “operably linked” refers to a juxtaposition wherein the components described are in a relationship permitting them to function in their intended manner. A regulatory sequence “operably linked” to a coding sequence is ligated in such a way that expression of the coding sequence is achieved under conditions compatible with the control sequences.
The term “regulatory sequences” includes promoters and enhancers and other expression regulation signals.
The term “promoter” is used in the normal sense of the art, e.g. an RNA polymerase binding site.
Enhanced expression of the nucleotide sequence encoding the enzyme having the specific properties as defined herein may also be achieved by the selection of regulatory regions, e.g. promoter, secretion leader and terminator regions that are not regulatory regions for the nucleotide sequence encoding the enzyme in nature.
Suitably, the nucleotide sequence of the present invention may be operably linked to at least a promoter.
Suitably, the nucleotide sequence encoding a lipid acyltransferase may be operably linked to at a nucleotide sequence encoding a terminator sequence. Examples of suitable terminator sequences for use in any one of the vectors, host cells, methods and/or uses of the present invention include: an .alpha.-amylase terminator sequence (for instance, CGGGACTTACCGAAAGAAACCATCAATGATGGTTTCTTTTTTGTTCATAAA—SEQ ID NO: 64), an alkaline protease terminator sequence (for instance, CAAGACTAAAGACCGTTCGCCCGTTTTTGCAATAAGCGGGCGAATCTTACATAAAAATA—SEQ ID NO: 65), a glutamic-acid specific terminator sequence (for instance, ACGGCCGTTAGATGTGACAGCCCGTTCCAAAAGGAAGCGGGCTGTCTTCGTGTATTATTGT—SEQ ID NO: 66), a levanase terminator sequence (for instance, TCTTTTAAAGGAAAGGCTGGAATGCCCGGCATTCCAGCCACATGATCATCGTTT—SEQ ID NO: 67) and a subtilisin E terminator sequence (for instance, GCTGACAAATAAAAAGAAGCAGGTATGGAGGAACCTGCTTCTTTTTACTATTATTG—SEQ ID NO: 119). Suitably, the nucleotide sequence encoding a lipid acyltransferase may be operably linked to an .alpha.-amylase terminator, such as a B. licheniformis .alpha.-amylase terminator.
Promoter
The promoter sequence to be used in accordance with the present invention may be heterologous or homologous to the sequence encoding a lipid acyltransferase.
The promoter sequence may be any promoter sequence capable of directing expression of a lipid acyltransferase in the host cell of choice.
Suitably, the promoter sequence may be homologous to a Bacillus species, for example B. licheniformis. Preferably, the promoter sequence is homologous to the host cell of choice.
Suitably the promoter sequence may be homologous to the host cell. “Homologous to the host cell” means originating within the host organism; i.e. a promoter sequence which is found naturally in the host organism.
Suitably, the promoter sequence may be selected from the group consisting of a nucleotide sequence encoding: an α-amylase promoter, a protease promoter, a subtilisin promoter, a glutamic acid-specific protease promoter and a levansucrase promoter.
Suitably the promoter sequence may be a nucleotide sequence encoding: the LAT (e.g. the alpha-amylase promoter from B. licheniformis, also known as AmyL), AprL (e.g. subtilisin Carlsberg promoter), EndoGluC (e.g. the glutamic-acid specific promoter from B. licheniformis), AmyQ (e.g. the alpha amylase promoter from B. amyloliquefaciens alpha-amylase promoter) and SacB (e.g. the B. subtilis levansucrase promoter).
Other examples of promoters suitable for directing the transcription of a nucleic acid sequence in the methods of the present invention include: the promoter of the Bacillus lentus alkaline protease gene (aprH),; the promoter of the Bacillus subtilis alpha-amylase gene (amyE); the promoter of the Bacillus stearothermophilus maltogenic amylase gene (amyM); the promoter of the Bacillus licheniformis penicillinase gene (penP); the promoters of the Bacillus subtilis xylA and xylB genes; and/or the promoter of the Bacillus thuringiensis subsp. tenebrionis CryIIIA gene.
In a preferred embodiment, the promoter sequence is an α-amylase promoter (such as a Bacillus licheniformis α-amylase promoter). Preferably, the promoter sequence comprises the −35 to −10 sequence of the B. licheniformis α-amylase promoter—see FIGS. 53 and 55.
The “−35 to −10 sequence” describes the position relative to the transcription start site. Both the “−35” and the “−10” are boxes, i.e. a number of nucleotides, each comprising 6 nucleotides and these boxes are separated by 17 nucleotides. These 17 nucleotides are often referred to as a “spacer”. This is illustrated in FIG. 55, where the −35 and the −10 boxes are underlined. For the avoidance of doubt, where “−35 to −10 sequence” is used herein it refers to a sequence from the start of the −35 box to the end of the −10 box i.e. including both the −35 box, the 17 nucleotide long spacer and the −10 box.
Signal Peptide
The lipid acyltransferase produced by a host cell by expression of the nucleotide sequence encoding the lipid acyltransferase may be secreted or may be contained intracellularly depending on the sequence and/or the vector used.
A signal sequence may be used to direct secretion of the coding sequences through a particular cell membrane. The signal sequences may be natural or foreign to the lipid acyltransferase coding sequence. For instance, the signal peptide coding sequence may be obtained form an amylase or protease gene from a Bacillus species, preferably from Bacillus licheniformis. 
Suitable signal peptide coding sequences may be obtained from one or more of the following genes: maltogenic α-amylase gene, subtilisin gene, beta-lactamase gene, neutral protease gene, prsA gene, and/or acyltransferase gene.
Preferably, the signal peptide is a signal peptide of B. licheniformis .alpha.-amylase, Aeromonas acyltransferase (for instance, mkkwfvellglialtvqa—SEQ ID NO: 21), B. subtilis subtilisin (for instance, mrskklwisllfaltliftmafsnmsaqa—SEQ ID NO: 22) or B. licheniformis subtilisin (for instance, mmrkksfwfgmltafmlyftmefsdsasa—SEQ ID NO: 23) Suitably, the signal peptide may be the signal peptide of B. licheniformis α-amylase.
However, any signal peptide coding sequence capable of directing the expressed lipid acyltransferase into the secretory pathway of a Bacillus host cell (preferably a B. licheniformis host cell) of choice may be used.
In some embodiments of the present invention, a nucleotide sequence encoding a signal peptide may be operably linked to a nucleotide sequence encoding a lipid acyltransferase of choice.
The lipid acyltransferase of choice may be expressed in a host cell as defined herein as a fusion protein.
Expression Vector
The term “expression vector” means a construct capable of in vivo or in vitro expression.
Preferably, the expression vector is incorporated in the genome of the organism, such as a B. licheniformis host. The term “incorporated” preferably covers stable incorporation into the genome.
The nucleotide sequence encoding a lipid acyltransferase as defined herein may be present in a vector, in which the nucleotide sequence is operably linked to regulatory sequences such that the regulatory sequences are capable of providing the expression of the nucleotide sequence by a suitable host organism (such as B. licheniformis), i.e. the vector is an expression vector.
The vectors of the present invention may be transformed into a suitable host cell as described above to provide for expression of a polypeptide having lipid acyltransferase activity as defined herein.
The choice of vector, e.g. plasmid, cosmid, virus or phage vector, genomic insert, will often depend on the host cell into which it is to be introduced. The present invention may cover other forms of expression vectors which serve equivalent functions and which are, or become, known in the art.
Once transformed into the host cell of choice, the vector may replicate and function independently of the host cell's genome, or may integrate into the genome itself.
The vectors may contain one or more selectable marker genes—such as a gene which confers antibiotic resistance e.g. ampicillin, kanamycin, chloramphenicol or tetracyclin resistance. Alternatively, the selection may be accomplished by co-transformation (as described in WO91/17243).
Vectors may be used in vitro, for example for the production of RNA or used to transfect or transform a host cell.
The vector may further comprise a nucleotide sequence enabling the vector to replicate in the host cell in question. Examples of such sequences are the origins of replication of plasmids pUC19, pACYC177, pUB110, pE194, pAMB1 and pIJ702.
Lipid Acyl Transferase
The nucleotide sequence encoding a lipid acyl transferase for use in any one of the methods and/or uses of the present invention may encode a natural lipid acyl transferase or a variant lipid acyl transferase.
The lipid acyl transferase for use in any one of the methods and/or uses of the present invention may be a natural lipid acyl transferase or a variant lipid acyl transferase.
For instance, the nucleotide sequence encoding a lipid acyl transferase for use in the present invention may be one as described in WO2004/064537, WO2004/064987, WO2005/066347, or WO2006/008508. These documents are incorporated herein by reference.
The term “lipid acyl transferase” as used herein preferably means an enzyme that has acyltransferase activity (generally classified as E.C. 2.3.1.x, for example 2.3.1.43), whereby the enzyme is capable of transferring an acyl group from a lipid to one or more acceptor substrates, such as one or more of the following: a sterol; a stanol; a carbohydrate; a protein; a protein subunit; a sugar alcohol, such as ascorbic acid and/or glycerol—preferably glycerol and/or a sterol, such as cholesterol.
Preferably, the lipid acyl transferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that is capable of transferring an acyl group from a phospholipid (as defined herein) to a sugar alcohol, such as ascorbic acid and/or glycerol and/or a sterol, preferably glycerol or a sterol, most preferably a sterol (e.g. cholesterol).
For some aspects the “acyl acceptor” according to the present invention may be any compound comprising a hydroxy group (—OH), such as for example, polyvalent alcohols, including glycerol; sterols; stanols; carbohydrates; hydroxy acids including fruit acids, citric acid, tartaric acid, lactic acid and ascorbic acid; proteins or a sub-unit thereof, such as amino acids, protein hydrolysates and peptides (partly hydrolysed protein) for example; and mixtures and derivatives thereof. Preferably, the “acyl acceptor” according to the present invention is not water. Preferably, the “acyl acceptor” according to the present invention is a sugar alcohol, such as a polyol, most preferably glycerol. For the purpose of this invention ascorbic acid is also considered a sugar-alcohol.
The acyl acceptor is preferably not a monoglyceride.
The acyl acceptor is preferably not a diglyceride
In one aspect, the lipid acyltransferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that may, as well as being able to transfer an acyl group from a lipid to glycerol, additionally be able to transfer the acyl group from a lipid to one or more of the following: a carbohydrate, a protein, a protein subunit, sterol and/or a stanol, preferably it is capable of transferring to both a sugar alcohol, such as ascorbic acid and/or glycerol, most preferably a sterol such as cholesterol, and/or plant sterols/stanols.
Preferably, the lipid substrate upon which the lipid acyl acts is one or more of the following lipids: a phospholipid, such as a lecithin, e.g. phosphatidylcholine and/or phosphatidylethanolamine.
This lipid substrate may be referred to herein as the “lipid acyl donor”. The term lecithin as used herein encompasses phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine and phosphatidylglycerol.
For some aspects, preferably the lipid acyl transferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that is incapable, or substantially incapable, of acting on a triglyceride and/or a 1-monoglyceride and/or 2-monoglyceride.
For some aspects, preferably the lipid acyl transferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that does not exhibit triacylglycerol lipase activity (E.C. 3.1.1.3) or does not exhibit significant triacylglycerol lipase activity (E.C. 3.1.1.3).
The ability to hydrolyse triglyceride (E.C. 3.1.1.3 activity) may be determined by lipase activity is determined according to Food Chemical Codex (3rd Ed., 1981, pp 492-493) modified to sunflower oil and pH 5.5 instead of olive oil and pH 6.5. The lipase activity is measured as LUS (lipase units sunflower) where 1 LUS is defined as the quantity of enzyme which can release 1 [mu]mol of fatty acids per minute from sunflower oil under the above assay conditions. Alternatively the LUT assay as defined in WO9845453 may be used. This reference is incorporated herein by reference.
The lipid acyl transferase for use in any one of the methods and/or uses of the present invention may be a lipid acyltransferase which is substantially incapable of acting on a triglyceride may have a LUS/mg of less than 1000, for example less than 500, such as less than 300, preferably less than 200, more preferably less than 100, more preferably less than 50, more preferably less than 20, more preferably less than 10, such as less than 5, less than 2, more preferably less than 1 LUS/mg. Alternatively LUT/mg activity is less than 500, such as less than 300, preferably less than 200, more preferably less than 100, more preferably less than 50, more preferably less than 20, more preferably less than 10, such as less than 5, less than 2, more preferably less than 1 LUT/mg.
The lipid acyl transferase for use in any one of the methods and/or uses of the present invention may be a lipid acyltransferase which is substantially incapable of acting on a monoglyceride. This may be determined by using mono-oleate (M7765 1-Oleoyl-rac-glycerol 99%) in place of the sunflower oil in the LUS assay. 1 MGHU is defined as the quantity of enzyme which can release 1 [mu]mol of fatty acids per minute from monoglyceride under the assay conditions.
The lipid acyl transferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase which is preferably substantially incapable of acting on a triglyceride may have a MGHU/mg of less than 5000, for example less than 1000, for example less than 500, such as less than 300, preferably less than 200, more preferably less than 100, more preferably less than 50, more preferably less than 20, more preferably less than 10, such as less than 5, less than 2, more preferably less than 1 MGHU/mg.
Suitably, the lipid acyltransferase for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that may exhibit one or more of the following phospholipase activities: phospholipase A2 activity (E.C. 3.1.1.4) and/or phospholipase A1 activity (E.C. 3.1.1.32). The lipid acyl transferase may also have phospholipase B activity (E.C 3.1.1.5).
Suitably, for some aspects the lipid acyltransferase may be capable of transferring an acyl group from a phospholipid to a sugar alcohol, preferably glycerol and/or ascorbic acid.
Suitably, for some aspects the lipid acyltransferase may be capable of transferring an acyl group from a phospholipid to a stanol and/or sterol, preferably cholesterol.
For some aspects, preferably the lipid acyltransferase for use any one of the methods and/or uses of the present invention encodes a lipid acyltransferase that is capable of transferring an acyl group from a phospholipid to a sterol and/or a stanol to form at least a sterol ester and/or a stanol ester.
The lipid acyltransferase may be capable of transferring an acyl group from a lipid to a polyol such as glycerol, and/or a sterol such as cholesterol or plant sterol/stanols. Thus, in one embodiment the “acyl acceptor” according to the present invention may be glycerol and/or cholesterol or plant sterol/stanols.
Preferably, the lipid acyltransferase enzyme may be characterised using the following criteria:

    
    
        the enzyme possesses acyl transferase activity which may be defined as ester transfer activity whereby the acyl part of an original ester bond of a lipid acyl donor is transferred to an acyl acceptor, preferably glycerol or cholesterol, to form a new ester; and
        the enzyme comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S.
    
    


Preferably, X of the GDSX motif is L or Y (SEQ ID NO: 121). More preferably, X of the GDSX motif is L (SEQ ID NO: 122). Thus, preferably the enzyme according to the present invention comprises the amino acid sequence motif GDSL (SEQ ID NO: 122).
The GDSX (SEQ ID NO: 120) motif is comprised of four conserved amino acids.
Preferably, the serine within the motif is a catalytic serine of the lipid acyl transferase enzyme. Suitably, the serine of the GDSX (SEQ ID NO: 120) motif may be in a position corresponding to Ser-16 in Aeromonas hydrophila lipid acyltransferase enzyme taught in Brumlik & Buckley (Journal of Bacteriology April 1996, Vol. 178, No. 7, p 2060-2064).
To determine if a protein has the GDSX (SEQ ID NO: 120) motif according to the present invention, the sequence is preferably compared with the hidden markov model profiles (HMM profiles) of the pfam database in accordance with the procedures taught in WO2004/064537 or WO2004/064987, incorporated herein by reference.
Preferably the lipid acyl transferase enzyme can be aligned using the Pfam00657 consensus sequence (for a full explanation see WO2004/064537 or WO2004/064987).
Preferably, a positive match with the hidden markov model profile (HMM profile) of the pfam00657 domain family indicates the presence of the GDSL (SEQ ID NO: 122) or GDSX (SEQ ID NO: 120) domain according to the present invention.
Preferably when aligned with the Pfam00657 consensus sequence the lipid acyltransferase for use in the methods or uses of the invention may have at least one, preferably more than one, preferably more than two, of the following, a GDSX (SEQ ID NO: 120) block, a GANDY (SEQ ID NO: 118) block, a HPT block. Suitably, the lipid acyltransferase may have a GDSX (SEQ ID NO: 120) block and a GANDY (SEQ ID NO: 118) block. Alternatively, the enzyme may have a GDSX (SEQ ID NO: 120) block and a HPT block. Preferably the enzyme comprises at least a GDSX (SEQ ID NO: 120) block. See WO2004/064537 or WO2004/064987 for further details.
Preferably, residues of the GANDY (SEQ ID NO: 118) motif are selected from GANDY (SEQ ID NO: 118), GGNDA (SEQ ID NO: 123), GGNDL (SEQ ID NO: 124), most preferably GANDY (SEQ ID NO: 118).
Preferably, when aligned with the Pfam00657 consensus sequence the enzyme for use in the methods or uses of the invention have at least one, preferably more than one, preferably more than two, preferably more than three, preferably more than four, preferably more than five, preferably more than six, preferably more than seven, preferably more than eight, preferably more than nine, preferably more than ten, preferably more than eleven, preferably more than twelve, preferably more than thirteen, preferably more than fourteen, of the following amino acid residues when compared to the reference A. hydrophilia polypeptide sequence, namely SEQ ID ID NO: 1: 28hid, 29hid, 30hid, 31hid, 32gly, 33Asp, 34Ser, 35hid, 130hid, 131Gly, 132Hid, 133Asn, 134Asp, 135hid, 309His.
The pfam00657 GDSX (SEQ ID NO: 120) domain is a unique identifier which distinguishes proteins possessing this domain from other enzymes.
The pfam00657 consensus sequence is presented in FIG. 3 as SEQ ID NO: 2. This is derived from the identification of the pfam family 00657, database version 6, which may also be referred to as pfam00657.6 herein.
The consensus sequence may be updated by using further releases of the pfam database (for example see WO2004/064537 or WO2004/064987).
In one embodiment, the lipid acyl transferase enzyme for use in any one of the methods and/or uses of the present invention is a lipid acyltransferase that may be characterised using the following criteria:

    
    
        (i) the enzyme possesses acyl transferase activity which may be defined as ester transfer activity whereby the acyl part of an original ester bond of a lipid acyl donor is transferred to acyl acceptor, preferably glycerol or cholesterol, to form a new ester, preferably monoglyceride or cholesterol ester respectfully;
        (ii) the enzyme comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S;
        (iii) the enzyme comprises His-309 or comprises a histidine residue at a position corresponding to His-309 in the Aeromonas hydrophila lipid acyltransferase enzyme shown in FIGS. 2 and 4 (SEQ ID NO: 1 or SEQ ID NO: 3).
    
    


Preferably, the amino acid residue of the GDSX motif is L (SEQ ID NO: 122).
In SEQ ID NO: 3 or SEQ ID NO: 1 the first 18 amino acid residues form a signal sequence. His-309 of the full length sequence, that is the protein including the signal sequence, equates to His-291 of the mature part of the protein, i.e. the sequence without the signal sequence.
In one embodiment, the lipid acyl transferase enzyme for use any one of the methods and uses of the present invention is a lipid acyltransferase that comprises the following catalytic triad: Ser-34, Asp-306 and His-309 or comprises a serine residue, an aspartic acid residue and a histidine residue, respectively, at positions corresponding to Ser-34, Asp-306 and His-309 in the Aeromonas hydrophila lipid acyl transferase enzyme shown in FIG. 4 (SEQ ID NO: 3) or FIG. 2 (SEQ ID NO: 1). As stated above, in the sequence shown in SEQ ID NO: 3 or SEQ ID NO: 1 the first 18 amino acid residues form a signal sequence. Ser-34, Asp-306 and His-309 of the full length sequence, that is the protein including the signal sequence, equate to Ser-16, Asp-288 and His-291 of the mature part of the protein, i.e. the sequence without the signal sequence. In the pfam00657 consensus sequence, as given in FIG. 3 (SEQ ID NO: 2) the active site residues correspond to Ser-7, Asp-345 and His-348.
In one embodiment, the lipid acyl transferase enzyme for use any one of the methods and/or uses of the present invention is a lipid acyltransferase that may be characterised using the following criteria:

    
    
        the enzyme possesses acyl transferase activity which may be defined as ester transfer activity whereby the acyl part of an original ester bond of a first lipid acyl donor is transferred to an acyl acceptor to form a new ester; and
        the enzyme comprises at least Gly-32, Asp-33, Ser-34, Asp-134 and His-309 or comprises glycine, aspartic acid, serine, aspartic acid and histidine residues at positions corresponding to Gly-32, Asp-33, Ser-34, Asp-306 and His-309, respectively, in the Aeromonas hydrophila lipid acyltransferase enzyme shown in SEQ ID NO: 3 or SEQ ID NO: 1.
    
    


Suitably, the lipid acyltransferase enzyme for use in any one of the methods and/or uses of the present invention may be encoded by one of the following nucleotide sequences:
(a) the nucleotide sequence shown as SEQ ID NO: 36 (see FIG. 29); (b) the nucleotide sequence shown as SEQ ID NO: 39 (see FIG. 32); (c) the nucleotide sequence shown as SEQ ID NO: 42 (see FIG. 35); (d) the nucleotide sequence shown as SEQ ID NO: 44 (see FIG. 37); (e) the nucleotide sequence shown as SEQ ID NO: 46 (see FIG. 39); (f) the nucleotide sequence shown as SEQ ID NO: 48 (see FIG. 41); (g) the nucleotide sequence shown as SEQ ID NO: 49 (see FIG. 57); (h) the nucleotide sequence shown as SEQ ID NO: 50 (see FIG. 58); (i) the nucleotide sequence shown as SEQ ID NO: 51 (see FIG. 59); (j) the nucleotide sequence shown as SEQ ID NO: 52 (see FIG. 60); (k) the nucleotide sequence shown as SEQ ID NO: 53 (see FIG. 61); (1) the nucleotide sequence shown as SEQ ID NO: 54 (see FIG. 62); (m) the nucleotide sequence shown as SEQ ID NO: 55 (see FIG. 63); (n) the nucleotide sequence shown as SEQ ID NO: 56 (see FIG. 64); (o) the nucleotide sequence shown as SEQ ID NO: 57 (see FIG. 65); (p) the nucleotide sequence shown as SEQ ID NO: 58 (see FIG. 66); (q) the nucleotide sequence shown as SEQ ID NO: 59 (see FIG. 67); (r) the nucleotide sequence shown as SEQ ID NO: 60 (see FIG. 68); (s) the nucleotide sequence shown as SEQ ID NO: 61 (see FIG. 69); (t) the nucleotide sequence shown as SEQ ID NO: 62 (see FIG. 70); (u) the nucleotide sequence shown as SEQ ID NO: 63 (see FIG. 71); (v) or a nucleotide sequence which has 70% or more, preferably 75% or more, identity with any one of the sequences shown as SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 or SEQ ID NO: 63.
Suitably the nucleotide sequence may have 80% or more, preferably 85% or more, more preferably 90% or more and even more preferably 95% or more identity with any one of the sequences shown as SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 or SEQ ID NO: 63.
In one embodiment, the nucleotide sequence encoding a lipid acyltransferase enzyme for use any one of the methods and uses of the present invention is a nucleotide sequence which has 70% or more, preferably 75% or more, identity with any one of the sequences shown as: SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 62, and SEQ ID NO: 63. Suitably the nucleotide sequence may have 80% or more, preferably 85% or more, more preferably 90% or more and even more preferably 95% or more identity with any one of the sequences shown as: SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 62, and SEQ ID NO: 63.
In one embodiment, the nucleotide sequence encoding a lipid acyltransferase enzyme for use in any one of the methods and uses of the present invention is a nucleotide sequence which has 70% or more, 75% or more, 80% or more, preferably 85% or more, more preferably 90% or more and even more preferably 95% or more identity the sequence shown as SEQ ID NO: 49.
Suitably, the lipid acyl transferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase that comprises one or more of the following amino acid sequences:
(i) the amino acid sequence shown as SEQ ID NO: 3 (ii) the amino acid sequence shown as SEQ ID NO: 4 (iii) the amino acid sequence shown as SEQ ID NO: 5 (iv) the amino acid sequence shown as SEQ ID No. 6 (v) the amino acid sequence shown as SEQ ID No. 7 (vi) the amino acid sequence shown as SEQ ID NO: 8 (vii) the amino acid sequence shown as SEQ ID NO: 9 (viii) the amino acid sequence shown as SEQ ID NO: 10 (ix) the amino acid sequence shown as SEQ ID NO: 11 (x) the amino acid sequence shown as SEQ ID NO: 12 (xi) the amino acid sequence shown as SEQ ID NO: 13 (xii) the amino acid sequence shown as SEQ ID NO: 14 (xiii) the amino acid sequence shown as SEQ ID NO: 1 (xiv) the amino acid sequence shown as SEQ ID No. 15 (xv) the amino acid sequence shown as SEQ ID NO: 16 (xvi) the amino acid sequence shown as SEQ ID NO: 17 (xvii) the amino acid sequence shown as SEQ ID NO: 18 (xviii) the amino acid sequence shown as SEQ ID NO: 34 (xix) the amino acid sequence shown as SEQ ID NO: 35 or an amino acid sequence which has 75%, 80%, 85%, 90%, 95%, 98% or more identity with any one of the sequences shown as SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14 or SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34 or SEQ ID NO: 35.
Suitably, the lipid acyl transferase enzyme for use any one of the methods and uses of the present invention may be a lipid acyltransferase that comprises either the amino acid sequence shown as SEQ ID NO: 3 or as SEQ ID NO: 4 or SEQ ID NO: 1 or SEQ ID NO: 15 or SEQ ID NO: 16, or SEQ ID NO: 34 or SEQ ID NO: 35 or comprises an amino acid sequence which has 75% or more, preferably 80% or more, preferably 85% or more, preferably 90% or more, preferably 95% or more, identity with the amino acid sequence shown as SEQ ID NO: 3 or the amino acid sequence shown as SEQ ID NO: 4 or the amino acid sequence shown as SEQ ID NO: 1 or the amino acid sequence shown as SEQ ID No. 15 or the amino acid sequence shown as SEQ ID NO: 16 or the amino acid sequence shown as SEQ ID NO: 34 or the amino acid sequence shown as SEQ ID NO: 35.
Suitably the lipid acyl transferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase that comprises an amino acid sequence which has 80% or more, preferably 85% or more, more preferably 90% or more and even more preferably 95% or more identity with any one of the sequences shown as SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34 or SEQ ID NO: 35.
Suitably, the lipid acyl transferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase that comprises one or more of the following amino acid sequences:
(a) an amino acid sequence shown as amino acid residues 1-100 of SEQ ID NO: 3 or SEQ ID NO: 1;
(b) an amino acid sequence shown as amino acids residues 101-200 of SEQ ID NO: 3 or SEQ ID NO: 1;
(c) an amino acid sequence shown as amino acid residues 201-300 of SEQ ID NO: 3 or SEQ ID NO: 1; or
(d) an amino acid sequence which has 75% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more identity to any one of the amino acid sequences defined in (a)-(c) above.
Suitably, the lipid acyl transferase enzyme for use in methods and uses of the present invention may comprise one or more of the following amino acid sequences:
(a) an amino acid sequence shown as amino acid residues 28-39 of SEQ ID NO: 3 or SEQ ID NO: 1;
(b) an amino acid sequence shown as amino acids residues 77-88 of SEQ ID NO: 3 or SEQ ID NO: 1;
(c) an amino acid sequence shown as amino acid residues 126-136 of SEQ ID NO: 3 or SEQ ID NO: 1;
(d) an amino acid sequence shown as amino acid residues 163-175 of SEQ ID NO: 3 or SEQ ID NO: 1;
(e) an amino acid sequence shown as amino acid residues 304-311 of SEQ ID NO: 3 or SEQ ID NO: 1; or
(f) an amino acid sequence which has 75% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more identity to any one of the amino acid sequences defined in (a)-(e) above.
In one aspect, the lipid acyl transferase enzyme for use any one of the methods and/or uses of the present invention is a lipid acyltransferase that may be the lipid acyl transferase from Candida parapsilosis as taught in EP 1 275 711. Thus in one aspect the lipid acyl transferase for use in the method and uses of the present invention may be a lipid acyl transferase comprising one of the amino acid sequences taught in SEQ ID NO: 17 or SEQ ID NO: 18.
Much by preference, the lipid acyl transferase enzyme for use in any one of the methods and uses of the present invention is a lipid acyltransferase that may be a lipid acyl transferase comprising the amino acid sequence shown as SEQ ID No. 16, or an amino acid sequence which has 75% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 98% or more, or even more preferably 99% or more identity to SEQ ID NO: 16. This enzyme could be considered a variant enzyme.
In one aspect, the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention is a lipid acyltransferase that may be a lecithin:cholesterol acyltransferase (LCAT) or variant thereof (for example a variant made by molecular evolution)
Suitable LCATs are known in the art and may be obtainable from one or more of the following organisms for example: mammals, rat, mice, chickens, Drosophila melanogaster, plants, including Arabidopsis and Oryza sativa, nematodes, fungi and yeast.
In one embodiment the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention is a lipid acyltransferase that may be the lipid acyltransferase obtainable, preferably obtained, from the E. coli strains TOP 10 harbouring pPet12aAhydro and pPet12aASalmo deposited by Danisco A/S of Langebrogade 1, DK-1001 Copenhagen K, Denmark under the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the purposes of Patent Procedure at the National Collection of Industrial, Marine and Food Bacteria (NCIMB) 23 St. Machar Street, Aberdeen Scotland, GB on 22 Dec. 2003 under accession numbers NCIMB 41204 and NCIMB 41205, respectively.
A lipid acyltransferase enzyme for use in any one of the methods and/or uses of the present invention may be a phospholipid glycerol acyl transferase. Phospholipid glycerol acyl transferases include those isolated from Aeromonas spp., preferably Aeromonas hydrophila or A. salmonicida, most preferably A. salmonicida or variants thereof.
Most preferred lipid acyl transferases for use in the present invention are encoded by SEQ ID NOS: 1, 3, 4, 15, 16, 34 and 35. It will be recognised by the skilled person that it is preferable that the signal peptides of the acyl transferase has been cleaved during expression of the transferase. The signal peptide of SEQ ID NOS: 1, 3, 4, 15 and 16 are amino acids 1-18. Therefore the most preferred regions are amino acids 19-335 for SEQ ID NO: 1 and SEQ ID NO: 3 (A. hydrophilia) and amino acids 19-336 for SEQ ID NO: 4, SEQ ID NO: 15 and SEQ ID NO: 16. (A. salmonicida). When used to determine the homology of identity of the amino acid sequences, it is preferred that the alignments as herein described use the mature sequence.
In one embodiment, suitably the lipid acyl transferase for use in the present invention comprises (or consists of) the amino acid sequence shown in SEQ ID NO: 16 or comprises (or consists of) an amino acid sequence which has at least 70%, at least 75%, at least 85%, at least 90%, at least 95%, at least 98% identity to SEQ ID NO: 16.
In one embodiment, suitably the lipid acyl transferase for use in the present invention is encoded by a nucleotide sequence comprising (or consisting of) a nucleotide sequence shown in SEQ ID NO: 68 or comprises (or consists of) a nucleotide sequence which has at least 70%, at least 75%, at least 85%, at least 90%, at least 95%, at least 98% identity to SEQ ID No. 68.
Therefore the most preferred regions for determining homology (identity) are amino acids 19-335 for SEQ ID NOS: 1 and 3 (A. hydrophilia) and amino acids 19-336 for SEQ ID Nos. 4, 15 and 16. (A. salmonicida). SEQ ID Nos. 34 and 35 are mature protein sequences of a lipid acyl transferase from A. hydrophilia and A. salmonicida respectively which may or may not undergo further post-translational modification.
A lipid acyltransferase enzyme for use any one of the methods and uses of the present invention may be a lipid acyltransferase that may also be isolated from Thermobifida, preferably T. fusca, most preferably that encoded by SEQ ID NO: 28.
Suitable lipid acyltransferases for use in accordance with the present invention and/or in the methods of the present invention may comprise any one of the following amino acid sequences and/or be encoded by the following nucleotide sequences:
a) a nucleic acid which encodes a polypeptide exhibiting lipid acyltransferase activity and is at least 70% identical (preferably at least 80%, more preferably at least 90% identical) with the polypeptide sequence shown in SEQ ID NO: 16 or with the polypeptide shown in SEQ ID NO: 68; b) a (isolated) polypeptide comprising (or consisting of) an amino acid sequence as shown in SEQ ID NO: 16 or SEQ ID NO: 68 or an amino acid sequence which is at least 70% identical (preferably at least 80% identical, more preferably at least 90% identical) with SEQ ID NO: 16 or SEQ ID NO: 68; c) a nucleic acid encoding a lipid acyltransferase, which nucleic acid comprises (or consists of) a nucleotide sequence shown as SEQ ID NO: 49 or a nucleotide sequence which is at least 70% identical (preferably at least 80%, more preferably at least 90% identical) with the nucleotide sequence shown as SEQ ID NO: 49; d) a nucleic acid which hybridises under medium or high stringency conditions to a nucleic acid probe comprising the nucleotide sequence shown as SEQ ID NO: 49 and encodes for a polypeptide exhibiting lipid acyltransferase activity; e) a nucleic acid which is a fragment of the nucleic acid sequences specified in a), c) or d); or f) a polypeptide which is a fragment of the polypeptide specified in b).
A lipid acyltransferase enzyme for use any one of the methods and uses of the present invention may be a lipid acyltransferase that may also be isolated from Streptomyces, preferable S. avermitis, most preferably that encoded by SEQ ID NO: 32. Other possible enzymes for use in the present invention from Streptomyces include those encoded by SEQ ID Nos. 5, 6, 9, 10, 11, 12, 13, 14, 31, and 33.
An enzyme for use in the invention may also be isolated from Corynebacterium, preferably C. efficiens, most preferably that encoded by SEQ ID NO: 29.
Suitably, the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase that comprises any one of the amino acid sequences shown as SEQ ID Nos. 37, 38, 40, 41, 43, 45, or 47 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith, or may be encoded by any one of the nucleotide sequences shown as SEQ ID Nos. 36, 39, 42, 44, 46, or 48 or a nucleotide sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith.
In one embodiment, the nucleotide sequence encoding a lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention is selected from the group consisting of:
a) a nucleic acid comprising a nucleotide sequence shown in SEQ ID NO: 36;
b) a nucleic acid which is related to the nucleotide sequence of SEQ ID NO: 36 by the degeneration of the genetic code; and

    
    
        c) a nucleic acid comprising a nucleotide sequence which has at least 70% identity with the nucleotide sequence shown in SEQ ID NO: 36.
    
    


In one embodiment, the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention is a lipid acyltransferase that comprises an amino acid sequence as shown in SEQ ID NO: 37 or an amino acid sequence which has at least 60% identity thereto.
In a further embodiment the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase comprising any one of the amino acid sequences shown as SEQ ID NOS: 37, 38, 40, 41, 43, 45 or 47 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith, or may be encoded by any one of the nucleotide sequences shown as SEQ ID No. 39, 42, 44, 46 or 48 or a nucleotide sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith.
In a further embodiment the lipid acyltransferase enzyme for use any one of the methods and/or uses of the present invention may be a lipid acyltransferase comprising any one of amino sequences shown as SEQ ID NOS: 38, 40, 41, 45 or 47 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith for the uses described herein.
In a further embodiment the lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be a lipid acyltransferase comprising any one of amino sequences shown as SEQ ID NOS: 38, 40, or 47 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith for the uses described herein.
More preferably in one embodiment the lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be a lipid acyltransferase comprising the amino acid sequence shown as SEQ ID NOS: 47 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith.
In another embodiment the lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase comprising the amino acid sequence shown as SEQ ID NOS: 43 or 44 or an amino acid sequence which has at least 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith.
In another embodiment the lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase comprising the amino acid sequence shown as SEQ ID NO: 41 or an amino acid sequence which has at least 70%, 75%, 80%, 85%, 90%, 95%, 96%, 97% or 98% identity therewith.
In one embodiment the lipid acyltransferase for use in any one of the methods and uses of the present invention may be encoded by a nucleic acid selected from the group consisting of:
a) a nucleic acid comprising a nucleotide sequence shown in SEQ ID NO: 36;

    
    
        b) a nucleic acid which is related to the nucleotide sequence of SEQ ID NO: 36 by the degeneration of the genetic code; and
        c) a nucleic acid comprising a nucleotide sequence which has at least 70% identity with the nucleotide sequence shown in SEQ ID NO: 36.
    
    


In one embodiment the lipid acyltransferase according to the present invention may be a lipid acyltransferase obtainable, preferably obtained, from the Streptomyces strains L130 or L131 deposited by Danisco A/S of Langebrogade 1, DK-1001 Copenhagen K, Denmark under the Budapest Treaty on the International Recognition of the Deposit of Microorganisms for the purposes of Patent Procedure at the National Collection of Industrial, Marine and Food Bacteria (NCIMB) 23 St. Machar Street, Aberdeen Scotland, GB on 25 Jun. 2004 under accession numbers NCIMB 41226 and NCIMB 41227, respectively.
Suitable nucleotide sequences encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention may encode a polynucleotide encoding a lipid acyltransferase (SEQ ID NO: 16); or may encode an amino acid sequence of a lipid acyltransferase (SEQ ID NO: 16).
A suitable lipid acyltransferases for use in any one of the methods and/or uses of the present invention may be an amino acid sequence which may be identified by alignment to the L131 (SEQ ID NO: 37) sequence using Align X, the Clustal W pairwise alignment algorithm of Vector NTI using default settings.
An alignment of the L131 and homologues from S. avermitilis and T. fusca illustrates that the conservation of the GDSX (SEQ ID NO: 120) motif (GDSY (SEQ ID NO: 125) in L131 and S. avermitilis and T. fusca), the GANDY (SEQ ID NO: 118) box, which is either GGNDA (SEQ ID NO: 123) or GGNDL (SEQ ID NO: 124), and the HPT block (considered to be the conserved catalytic histidine). These three conserved blocks are highlighted in FIG. 42.
When aligned to either the pfam Pfam00657 consensus sequence (as described in WO04/064987) and/or the L131 sequence herein disclosed (SEQ ID No 37) it is possible to identify three conserved regions, the GDSX (SEQ ID NO: 120) block, the GANDY (SEQ ID NO: 118) block and the HTP block (see WO04/064987 for further details).
When aligned to either the pfam Pfam00657 consensus sequence (as described in WO04/064987) and/or the L131 sequence herein disclosed (SEQ ID NO: 37)

    
    
        i) The lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase that has a GDSX (SEQ ID NO: 120) motif, more preferably a GDSX (SEQ ID NO: 120) motif selected from GDSL (SEQ ID NO: 122) or GDSY (SEQ ID NO: 125) motif
    
    


and/or

    
    
        ii) The lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase that, has a GANDY (SEQ ID NO: 118) block, more preferably a GANDY (SEQ ID NO: 118) block comprising amino GGNDx (SEQ ID NO: 126), more preferably GGNDA (SEQ ID NO: 123) or GGNDL (SEQ ID NO: 124).
    
    


and/or

    
    
        iii) The lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase that has preferably an HTP block.
    
    


and preferably

    
    
        iv) the lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase that has preferably a GDSX (SEQ ID NO: 120) or GDSY (SEQ ID NO: 125) motif, and a GANDY (SEQ ID NO: 118) block comprising amino GGNDx (SEQ ID NO: 126), preferably GGNDA (SEQ ID NO: 123) or GGNDL (SEQ ID NO: 124), and a HTP block (conserved histidine).
    
    


Without wishing to be bound by theory the reaction of the lipid acyltransferase and lecithin naturally present in the UHT milk can be used to change the surface activity of the native components of the milk and/or it can be used to reduce the amount of cholesterol in the milk.
The lipid acyltransferase as used herein may be referred to as a glycerophospholipid cholesterol acyltransferase. In other words the lipid acyltransferase for use in the present invention preferably has the ability to “hydrolyse” phospholipids and at the same time esterify cholesterol with the free fatty acid from the hydrolyzation this is effective a tranferase reaction (i.e. an interesterification and/or a transesterification reaction.
The degree of “hydrolysis” can be described as the ratio of phosphatidylcholine (PC) and/or phosphatidylethanolamine (PE) converted into lyso-PC or lyso-PE respectively. By the enzymatic hydrolyzation of PC into lyso-PC, the ratio between the hydrophilic part of the phospholipid molecule (polar head group) and the hydrophobic part (fatty acid chains) is alterated. By removing one fatty acid (saturated and/or unsaturated fatty acids) the hydrophobic part is reduced, thus making the entire molecule more hydrophilic. Furthermore the sterical molecule conformation may be changed, which may influence phase structures (e.g. micellation) formed by the molecules in dispersion, as well as interactions with other molecules like e.g. milk proteins.
Lyso-lecithin products are known to possess improved emulsifying properties. With a high degree of interesterification and/or transesterification it is possible to obtain smaller mean oil droplet sizes in a comparative emulsification test.
By changing cholesterol into cholesterol-ester along with a change of PC and PE to lyso-PC and lyso-PE (which both have superior surface activity compared to normal PC/PE) it is possible to produce UHT milk products without cholesterol and with improved emulsion stability. This is important in the production of UHT milk and in particular in the production of flavored UHT milk, where one of the main defects is related to low emulsion stability and a high rate of creaming.




The use of the lipid acyltransferase as defined herein results in smaller particles in the milk which is an advantage in UHT milk, where creaming is very often seen as a defect.
The function of lipid acyltransferase is that cholesterol and phospholipids will be changed into cholesterol-esters and lyso-phospholipids, giving two resulting components with surface-active properties in relation to O/W emulsions. It has been shown that lipid acyltransferases promote increased stability against creaming as well as reduced cholesterol level in UHT milk. Thus the final products will contain no or significantly reduced cholesterol and have an improved emulsion stability.
The enzyme according to the present invention is preferably not a phospholipase enzyme, such as a phospholipase A1 classified as E.C. 3.1.1.32 or a phospholipase A2 classified as E.C. 3.1.1.4.
Variant Lipid Acyl Transferase
In a preferred embodiment the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention may encode a lipid acyltransferase that is a variant lipid acyl transferase.
Variants which have an increased activity on phospholipids, such as increased hydrolytic activity and/or increased transferase activity, preferably increased transferase activity on phospholipids may be used.
Preferably the variant lipid acyltransferase is prepared by one or more amino acid modifications of the lipid acyl transferases as defined hereinabove.
Suitably, the lipid acyltransferase for use in any one of the methods and uses of the present invention may be a lipid acyltransferase that may be a variant lipid acyltransferase, in which case the enzyme may be characterised in that the enzyme comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S, and wherein the variant enzyme comprises one or more amino acid modifications compared with a parent sequence at any one or more of the amino acid residues defined in set 2 or set 4 or set 6 or set 7 (as defined WO2005/066347 and hereinbelow).
For instance the variant lipid acyltransferase may be characterised in that the enzyme comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S, and wherein the variant enzyme comprises one or more amino acid modifications compared with a parent sequence at any one or more of the amino acid residues detailed in set 2 or set 4 or set 6 or set 7 (as defined in WO2005/066347 and hereinbelow) identified by said parent sequence being structurally aligned with the structural model of P10480 defined herein, which is preferably obtained by structural alignment of P10480 crystal structure coordinates with 1IVN.PDB and/or 1DEO.PDB as defined WO2005/066347 and hereinbelow.
In a further embodiment a lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be a variant lipid acyltransferase that may be characterised in that the enzyme comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S, and wherein the variant enzyme comprises one or more amino acid modifications compared with a parent sequence at any one or more of the amino acid residues taught in set 2 identified when said parent sequence is aligned to the pfam consensus sequence (SEQ ID NO: 2—FIG. 3) and modified according to a structural model of P 10480 to ensure best fit overlap as defined WO2005/066347 and hereinbelow.
Suitably a lipid acyltransferase for use in any one of the methods and uses of the present invention may be a variant lipid acyltransferase enzyme that may comprise an amino acid sequence, which amino acid sequence is shown as SEQ ID NO: 34, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30—SEQ ID NO: 32, SEQ ID NO: 33 or SEQ ID NO: 35 except for one or more amino acid modifications at any one or more of the amino acid residues defined in set 2 or set 4 or set 6 or set 7 (as defined WO2005/066347 and hereinbelow) identified by sequence alignment with SEQ ID NO: 34.
Alternatively the lipid acyltransferase may be a variant lipid acyltransferase enzyme comprising an amino acid sequence, which amino acid sequence is shown as SEQ ID NO: 34, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 32, SEQ ID NO: 33 or SEQ ID NO: 35 except for one or more amino acid modifications at any one or more of the amino acid residues defined in set 2 or set 4 or set 6 or set 7 as defined WO2005/066347 and hereinbelow, identified by said parent sequence being structurally aligned with the structural model of P10480 defined herein, which is preferably obtained by structural alignment of P10480 crystal structure coordinates with 1IVN.PDB and/or 1DEO.PDB as taught within WO2005/066347 and hereinbelow.
Alternatively, the lipid acyltransferase may be a variant lipid acyltransferase enzyme comprising an amino acid sequence, which amino acid sequence is shown as SEQ ID NO: 34, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 32, SEQ ID NO: 33 or SEQ ID NO: 35 except for one or more amino acid modifications at any one or more of the amino acid residues taught in set 2 identified when said parent sequence is aligned to the pfam consensus sequence (SEQ ID NO: 2) and modified according to a structural model of P10480 to ensure best fit overlap as taught within WO2005/066347 and hereinbelow.
Preferably, the parent enzyme is an enzyme which comprises, or is homologous to, the amino acid sequence shown as SEQ ID NO: 34 and/or SEQ ID NO: 15 and/or SEQ ID No. 35.
Preferably, the lipid acyltransferase may be a variant enzyme which comprises an amino acid sequence, which amino acid sequence is shown as SEQ ID NO: 34 or SEQ ID NO: 35 except for one or more amino acid modifications at any one or more of the amino acid residues defined in set 2 or set 4 or set 6 or set 7 as defined in WO2005/066347 and hereinbelow.
Definition of Sets
Amino Acid Set 1:
Amino acid set 1 (note that these are amino acids in 1IVN—FIG. 53 and FIG. 54) (residues at positions 8-12, 69-76, and 106-110 disclosed as SEQ ID NOS 127-129, respectively) Gly8, Asp9, Ser10, Leu11, Ser12, Tyr15, Gly44, Asp45, Thr46, Glu69, Leu70, Gly71, Gly72, Asn73, Asp74, Gly75, Leu76, Gln106, Ile107, Arg108, Leu109, Pro110, Tyr113, Phe121, Phe139, Phe140, Met141, Tyr145, Met151, Asp154, His157, Gly155, Ile156, Pro158 The highly conserved motifs, such as GDSX (SEQ ID NO: 120) and catalytic residues, were deselected from set 1 (residues underlined). For the avoidance of doubt, set 1 defines the amino acid residues within 10 .ANG. of the central carbon atom of a glycerol in the active site of the 1IVN model.
Amino Acid Set 2:
Amino acid set 2 (note that the numbering of the amino acids refers to the amino acids in the P10480 mature sequence) (residues at positions 159-172 disclosed as SEQ ID NO: 130)
Leu17, Lys22, Met23, Gly40, Asn80, Pro81, Lys82, Asn87, Asn88, Trp111, Val112, Ala114, Tyr117, Leu118, Pro156, Gly159, Gln160, Asn161, Pro162, Ser163, Ala164, Arg165, Ser166, Gln167, Lys168, Val169, Val170, Glu171, Ala172, Tyr179, His180, Asn181, Met209, Leu210, Arg211, Asn215, Lys284, Met285, Gln289 and Val290.

Table of Selected Residues in Set 1 Compared with Set 2 (Column 1 Discloses Residues at Positions 8-12, 69-76, 106-110, and 154-158, as SEQ ID NOS 127-129 And 131, Respectively; Column 2 Discloses Residues at Positions 32-36, 129-136, and 306-310 as SEQ ID NOS 132-134, Respectively; Column 4 Discloses Residues at Positions 159-172 as SEQ ID NO: 130):














IVN model
P10480



IVN A. hyd homologue
Mature sequence Residue













PFAM
Structure
Number






Gly8
Gly32





Asp9
Asp33





Ser10
Ser34





Leu11
Leu35

Leu17



Ser12
Ser36

Ser18






Lys22






Met23



Tyr15
Gly58

Gly40



Gly44
Asn98

Asn80



Asp45
Pro99

Pro81



Thr46
Lys100

Lys82






Asn87






Asn88



Glu69
Trp129

Trp111



Leu70
Val130

Val112



Gly71
Gly131





Gly72
Ala132

Ala114



Asn73
Asn133





Asp74
Asp134





Gly75
Tyr135

Tyr117



Leu76
Leu136

Leu118



Gln106

Pro174
Pro156



Ile107

Gly177
Gly159



Arg108

Gln178
Gln160



Leu109

Asn179
Asn161



Pro110

180 to 190
Pro162



Tyr113


Ser163






Ala164






Arg165






Ser166






Gln167






Lys168






Val169






Val170






Glu171






Ala172



Phe121
His198
Tyr197
Tyr179





His198
His180





Asn199
Asn181



Phe139
Met227

Met209



Phe140
Leu228

Leu210



Met141
Arg229

Arg211



Tyr145
Asn233

Asn215






Lys284



Met151
Met303

Met285



Asp154
Asp306





Gly155
Gln307

Gln289



Ile156
Val308

Val290



His157
His309





Pro158
Pro310









Amino Acid Set 3:

Amino acid set 3 is identical to set 2 but refers to the Aeromonas salmonicida (SEQ ID NO: 4) coding sequence, i.e. the amino acid residue numbers are 18 higher in set 3 as this reflects the difference between the amino acid numbering in the mature protein (SEQ ID NO: 34) compared with the protein including a signal sequence (SEQ ID NO: 3).
The mature proteins of Aeromonas salmonicida GDSX (‘GDSX’ disclosed as SEQ ID NO: 120) (SEQ ID NO: 4) and Aeromonas hydrophila GDSX (‘GDSX’ disclosed as SEQ ID NO: 120) (SEQ ID NO: 34) differ in five amino acids. These are Thr3Ser, Gln182Lys, Glu309Ala, Ser310Asn, and Gly318-, where the salmonicida residue is listed first and the hydrophila residue is listed last. The hydrophila protein is only 317 amino acids long and lacks a residue in position 318. The Aeromonas salmonicida GDSX (‘GDSX’ disclosed as SEQ ID NO: 120) has considerably high activity on polar lipids such as galactolipid substrates than the Aeromonas hydrophila protein. Site scanning was performed on all five amino acid positions.
Amino Acid Set 4:
Amino acid set 4 is S3, Q182, E309, S310, and -318.
Amino Acid Set 5:
F13S, D15N, S18G, S18V, Y30F, D116N, D116E, D157 N, Y226F, D228N Y230F.
Amino Acid Set 6:
Amino acid set 6 is Ser3, Leu17, Lys22, Met23, Gly40, Asn80, Pro81, Lys82, Asn 87, Asn88, Trp111, Val112, Ala114, Tyr117, Leu118, Pro156, Gly159, Gln160, Asn161, Pro162, Ser163, Ala164, Arg165, Ser166, Gln167, Lys168, Val169, Val170, Glu171, Ala172, Tyr179, His180, Asn181, Gln182, Met209, Leu210, Arg211, Asn215, Lys284, Met285, Gln289, Val290, Glu309, Ser310, -318. Residues at positions 159-172 and 179-182 disclosed as SEQ ID NOS 130 and 135, respectively.
The numbering of the amino acids in set 6 refers to the amino acids residues in P 10480 (SEQ ID NO: 3)—corresponding amino acids in other sequence backbones can be determined by homology alignment and/or structural alignment to P10480 and/or 1IVN.
Amino Acid Set 7:
Amino acid set 7 is Ser3, Leu17, Lys22, Met23, Gly40, Asn80, Pro81, Lys82, Asn 87, Asn88, Trp111, Val112, Ala114, Tyr117, Leu118, Pro156, Gly159, Gln160, Asn161, Pro162, Ser163, Ala164, Arg165, Ser166, Gln167, Lys168, Val169, Val170, Glu171, Ala172, Tyr179, His180, Asn181, Gln182, Met209, Leu210, Arg211, Asn215, Lys284, Met285, Gln289, Val290, Glu309, Ser310, -318, Y30X (where X is selected from A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W), Y226X (where X is selected from A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W), Y230X (where X is selected from A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W), S18X (where X is selected from A, C, D, E, F, H, I, K, L, M, N, P, Q, R, T, W or Y), D157X (where X is selected from A, C, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W or Y). Residues at positions 159-172 and 179-182 disclosed as SEQ ID NOS 130 and 135, respectively.
The numbering of the amino acids in set 7 refers to the amino acids residues in P10480 (SEQ ID NO: 3)—corresponding amino acids in other sequence backbones can be determined by homology alignment and/or structural alignment to P10480 and/or 1IVN).
Suitably, the variant enzyme comprises one or more of the following amino acid modifications compared with the parent enzyme:
S3E, A, G, K, M, Y, R, P, N, T or G
E309Q, R or A, preferably Q or R
-318Y, H, S or Y, preferably Y.
Preferably, X of the GDSX motif is L (SEQ ID NO: 122). Thus, preferably the parent enzyme comprises the amino acid motif GDSL (SEQ ID NO: 122).
Suitably, said first parent lipid acyltransferase may comprise any one of the following
amino acid sequences: SEQ ID NO: 34, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 32, SEQ ID NO: 33 or SEQ ID NO: 35.
Suitably, said second related lipid acyltransferase may comprise any one of the following amino acid sequences: SEQ ID NO: 3, SEQ ID NO: 34, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 1, SEQ ID NO: 15, SEQ ID NO: 25, SEQ ID NO: 26, SEQ ID NO: 27, SEQ ID NO: 28, SEQ ID NO: 29, SEQ ID NO: 30, SEQ ID NO: 32, SEQ ID NO: 33 or SEQ ID NO: 35.
The variant enzyme must comprise at least one amino acid modification compared with the parent enzyme. In some embodiments, the variant enzyme may comprise at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably at least 6, preferably at least 7, preferably at least 8, preferably at least 9, preferably at least 10 amino acid modifications compared with the parent enzyme.
When referring to specific amino acid residues herein the numbering is that obtained from alignment of the variant sequence with the reference sequence shown as SEQ ID NO: 34 or SEQ ID NO: 35.
In one aspect preferably the variant enzyme comprises one or more of the following amino acid substitutions:
S3A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; and/or
L17A, C, D, E, F, G, H, I, K, M, N, P, Q, R, S, T, V, W, or Y; and/or
S18A, C, D, E, F, H, I, K, L, M, N, P, Q, R, T, W, or Y; and/or
K22A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
M23A, C, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, or Y; and/or
Y30A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W; and/or
G40A, C, D, E, F, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
N80A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
P81A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; and/or
K82A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
N87A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
N88A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
W111A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W or Y; and/or
V112A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; and/or
A114C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
Y117A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W; and/or
L118A, C, D, E, F, G, H, I, K, M, N, P, Q, R, S, T, V, W, or Y; and/or
P156A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; and/or
D157A, C, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
G159A, C, D, E, F, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
Q160A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y; and/or
N161A, C, D, E, F, G, H, I, K, L, M P, Q, R, S, T, V, W, or Y; and/or
P162A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W, or Y; and/or
S163A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; and/or
A164C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
R165A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W, or Y; and/or
S166A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y; and/or
Q167A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y; and/or
K168A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
V169A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; and/or
V170A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; and/or
E171A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
A172C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
Y179A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W; and/or
H180A, C, D, E, F, G, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
N181A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W, or Y; and/or
Q182A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y, preferably K; and/or
M209A, C, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, or Y; and/or
L210 A, C, D, E, F, G, H, I, K, M, N, P, Q, R, S, T, V, W, or Y; and/or
R211A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
N215 A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
Y226A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V, or W; and/or
Y230A, C, D, E, G, H, I, K, L, M, N, P, Q, R, S, T, V or W; and/or
K284A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
M285A, C, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W, or Y; and/or
Q289A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W, or Y; and/or
V290A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W, or Y; and/or
E309A, C, D, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, or Y; and/or
S310A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W, or Y.
In addition or alternatively thereto there may be one or more C-terminal extensions. Preferably the additional C-terminal extension is comprised of one or more aliphatic amino acids, preferably a non-polar amino acid, more preferably of I, L, V or G. Thus, the present invention further provides for a variant enzyme comprising one or more of the following C-terminal extensions: 318I, 318L, 318V, 318G.
Preferred variant enzymes may have a decreased hydrolytic activity against a phospholipid, such as phosphatidylcholine (PC), may also have an increased transferase activity from a phospholipid.
Preferred variant enzymes may have an increased transferase activity from a phospholipid, such as phosphatidylcholine (PC), these may also have an increased hydrolytic activity against a phospholipid.
Modification of one or more of the following residues may result in a variant enzyme having an increased absolute transferase activity against phospholipid:
S3, D157, S310, E309, Y179, N215, K22, Q289, M23, H180, M209, L210, R211, P81, V112, N80, L82, N88; N87
Specific preferred modifications which may provide a variant enzyme having an improved transferase activity from a phospholipid may be selected from one or more of the following:
S3A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W or Y; preferably N, E, K, R, A, P or M, most preferably S3A
D157A, C, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W or Y; preferably D157S, R, E, N, G, T, V, Q, K or C
S310A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W or Y; preferably S310T
-318 E
E309A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, T, V, W or Y; preferably E309 R, E, L, R or A
Y179A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V or W; preferably Y179 D, T, E, R, N, V, K, Q or S, more preferably E, R, N, V, K or Q
N215A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W or Y; preferably N215 S, L, R or Y
K22A, C, D, E, F, G, H, I, L, M, N, P, Q, R, S, T, V, W or Y; preferably K22 E, R, C or A
Q289A, C, D, E, F, G, H, I, K, L, M, N, P, R, S, T, V, W or Y; preferably Q289 R, E, G, P or N
M23A, C, D, E, F, G, H, I, K, L N, P, Q, R, S, T, V, W or Y; preferably M23 K, Q, L, G, T or S
H180A, C, D, E, F, G, I, K, L, M, P, Q, R, S, T, V, W or Y; preferably H180 Q, R or K
M209 A, C, D, E, F, G, H, I, K, L, N, P, Q, R, S, T, V, W or Y; preferably M209 Q, S, R, A, N, Y, E, V or L
L210A, C, D, E, F, G, H, I, K, M, N, P, Q, R, S, T, V, W or Y; preferably L210 R, A, V, S, T, I, W or M
R211A, C, D, E, F, G, H, I, K, L, M, N, P, Q, S, T, V, W or Y; preferably R211T
P81A, C, D, E, F, G, H, I, K, L, M, N, Q, R, S, T, V, W or Y; preferably P81G
V112A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, W or Y; preferably V112C
N80A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W or Y; preferably N80 R, G, N, D, P, T, E, V, A or G
L82A, C, D, E, F, G, H, I, M, N, P, Q, R, S, T, V, W or Y; preferably L82N, S or E
N88A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W or Y; preferably N88C
N87A, C, D, E, F, G, H, I, K, L, M, P, Q, R, S, T, V, W or Y; preferably N87M or G
Preferred modification of one or more of the following residues results in a variant enzyme having an increased absolute transferase activity against phospholipid:
S3 N, R, A, G
M23 K, Q, L, G, T, S
H180 R
L82 G
Y179 E, R, N, V, K or Q
E309 R, S, L or A
One preferred modification is N80D. This is particularly the case when using the reference sequence SEQ ID NO: 35 as the backbone. Thus, the reference sequence may be SEQ ID NO: 16. This modification may be in combination with one or more further modifications. Therefore in a preferred embodiment of the present invention the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and uses of the present invention may encode a lipid acyltransferase that comprises SEQ ID No. 35 or an amino acid sequence which has 75% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 98% or more, or even more preferably 99% or more identity to SEQ ID NO: 35.
As noted above, when referring to specific amino acid residues herein the numbering is that obtained from alignment of the variant sequence with the reference sequence shown as SEQ ID NO: 34 or SEQ ID NO: 35
Much by preference, the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and uses of the present invention may encode a lipid comprising the amino acid sequence shown as SEQ ID NO: 16 or the amino acid sequence shown as SEQ ID NO: 68, or an amino acid sequence which has 70% or more, preferably 75% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, even more preferably 98% or more, or even more preferably 99% or more identity to SEQ ID NO: 16 or SEQ ID NO: 68. This enzyme may be considered a variant enzyme.
For the purposes of the present invention, the degree of identity is based on the number of sequence elements which are the same. The degree of identity in accordance with the present invention for amino acid sequences may be suitably determined by means of computer programs known in the art, such as Vector NTI 10 (Invitrogen Corp.). For pairwise alignment the score used is preferably BLOSUM62 with Gap opening penalty of 10.0 and Gap extension penalty of 0.1.
Suitably, the degree of identity with regard to an amino acid sequence is determined over at least 20 contiguous amino acids, preferably over at least 30 contiguous amino acids, preferably over at least 40 contiguous amino acids, preferably over at least 50 contiguous amino acids, preferably over at least 60 contiguous amino acids.
Suitably, the degree of identity with regard to an amino acid sequence may be determined over the whole sequence.
Suitably, the nucleotide sequence encoding a lipid acyltransferase or the lipid acyl transferase enzyme for use in the present invention may be obtainable, preferably obtained, from organisms from one or more of the following genera: Aeromonas, Streptomyces, Saccharomyces, Lactococcus, Mycobacterium, Streptococcus, Lactobacillus, Desulfitobacterium, Bacillus, Campylobacter, Vibrionaceae, Xylella, Sulfolobus, Aspergillus, Schizosaccharomyces, Listeria, Neisseria, Mesorhizobium, Ralstonia, Xanthomonas, Candida, Thermobifida and Corynebacterium. 
Suitably, the nucleotide sequence encoding a lipid acyltransferase or the lipid acyl transferase enzyme for use in the present invention may be obtainable, preferably obtained, from one or more of the following organisms: Aeromonas hydrophila, Aeromonas salmonicida, Streptomyces coelicolor, Streptomyces rimosus, Mycobacterium, Streptococcus pyogenes, Lactococcus lactis, Streptococcus pyogenes, Streptococcus thermophilus, Streptomyces thermosacchari, Streptomyces avermitilis Lactobacillus helveticus, Desulfitobacterium dehalogenans, Bacillus sp, Campylobacter jejuni, Vibrionaceae, Xylella fastidiosa, Sulfolobus solfataricus, Saccharomyces cerevisiae, Aspergillus terreus, Schizosaccharomyces pombe, Listeria innocua, Listeria monocytogenes, Neisseria meningitidis, Mesorhizobium loti, Ralstonia solanacearum, Xanthomonas campestris, Xanthomonas axonopodis, Candida parapsilosis Thermobifida fusca and Corynebacterium efficiens. 
In one aspect, preferably the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention encodes a lipid acyl transferase enzyme according to the present invention is obtainable, preferably obtained or derived, from one or more of Aeromonas spp., Aeromonas hydrophila or Aeromonas salmonicida. 
In one aspect, preferably the lipid acyltransferase for use in any one of the methods and/or uses of the present invention is a lipid acyl transferase enzyme obtainable, preferably obtained or derived, from one or more of Aeromonas spp., Aeromonas hydrophila or Aeromonas salmonicida. 
Enzymes which function as lipid acyltransferases in accordance with the present invention can be routinely identified using the assay taught herein below:
Assay for Transferase Activity
The transferase activity is preferably measured by the molar amount of cholesterol ester formed by acyltransfer from phospholipids and/or lipids in milk to cholesterol relative to the amount of cholesterol originally available.
Milk is incubated with enzyme or water (as control) for 30 minutes at 40° C.
Milk lipids are isolated by solvent extraction and the isolated lipids are analysed by GLC.
Based on GLC analysis the amount of cholesterol (CHL), cholesterol ester (CHLE) and free fatty acids (FFA) are calculated.




  
    %
    ⁢
    
      
    
    ⁢
    Transferase
  
  =
  
    
      
        (
        
          
            CHLE
            ⁡
            
              (
              t
              )
            
          
          -
          
            CHLE
            ⁡
            
              (
              0
              )
            
          
        
        )
      
      ×
      100
    
    
      
        CHLE
        ⁡
        
          (
          t
          )
        
      
      -
      
        CHLE
        ⁡
        
          (
          0
          )
        
      
      +
      
        (
        
          
            FFA
            ⁡
            
              (
              t
              )
            
          
          -
          
            FFA
            ⁡
            
              (
              0
              )
            
          
        
      
    
  




Where

CHLE(0)=Mol/l Cholesterol ester Control

CHLE(t)=Mol/l Cholesterol ester Enzyme treatment

FFA(0)=Mol/l Free fatty acids Control

FFA(t)=Mol/l Free fatty acids Enzyme treatment

GLC Analysis May be Carried Out as Follows:

GLC Analysis

Perkin Elmer Autosystem 9000 Capillary Gas Chromatograph equipped with WCOT fused silica column 12.5 m×0.25 mm ID×0.1μ film thickness 5% phenyl-methyl-silicone (CP Sil 8 CB from Chrompack).
Carrier gas: Helium.
Injector. PSSI cold split injection (initial temp 50° C. heated to 385° C.), volume 1.0 μl
Detector FID: 395° C.












Oven program:











1
2
3















Oven temperature, ° C.
90
280
350



Isothermal, time, min.
1
0
10



Temperature rate, ° C./min.
15
4









Sample preparation: 30 mg of sample was dissolved in 9 ml Heptane:Pyridin, 2:1 containing internal standard heptadecane, 0.5 mg/ml. 300 μl sample solution was transferred to a crimp vial, 300 μl MSTFA (N-Methyl-N-trimethylsilyl-trifluoraceamid) was added and reacted for 20 minutes at 60° C.
Calculation: Response factors for mono-di-triglycerides and free fatty acid were determined from Standard 2 (mono-di-triglyceride), for Cholesterol, Cholesteryl palmitate and Cholesteryl stearate the response factors were determined from pure reference material (weighing for pure material 10 mg).
Using this assay, lipid acyltransferases/lipid acyl transferase in accordance with the present invention are those which have at least 5% transferase activity, preferably at least 10% transferase activity, preferably at least 15%, 20%, 25% 26%, 28%, 30%, 40% 50%, 60% or 75% transferase activity.
The term “transferase” as used herein is interchangeable with the term “lipid acyltransferase”.
Suitably, the lipid acyltransferase as defined herein catalyses one or more of the following reactions: interesterification, transesterification, alcoholysis, hydrolysis.
The term “interesterification” refers to the enzymatic catalysed transfer of acyl groups between a lipid donor and lipid acceptor, wherein the lipid donor is not a free acyl group.
The term “transesterification” as used herein means the enzymatic catalysed transfer of an acyl group from a lipid donor (other than a free fatty acid) to an acyl acceptor (other than water).
As used herein, the term “alcoholysis” refers to the enzymatic cleavage of a covalent bond of an acid derivative by reaction with an alcohol ROH so that one of the products combines with the H of the alcohol and the other product combines with the OR group of the alcohol.
As used herein, the term “alcohol” refers to an alkyl compound containing a hydroxyl group.
As used herein, the term “hydrolysis” refers to the enzymatic catalysed transfer of an acyl group from a lipid to the OH group of a water molecule.
The term “without increasing or without substantially increasing the free fatty acids” as used herein means that preferably the lipid acyl transferase according to the present invention has 100% transferase activity (i.e. transfers 100% of the acyl groups from an acyl donor onto the acyl acceptor, with no hydrolytic activity); however, the enzyme may transfer less than 100% of the acyl groups present in the lipid acyl donor to the acyl acceptor. In which case, preferably the acyltransferase activity accounts for at least 5%, more preferably at least 10%, more preferably at least 20%, more preferably at least 30%, more preferably at least 40%, more preferably 50%, more preferably at least 60%, more preferably at least 70%, more preferably at least 80%, more preferably at least 90% and more preferably at least 98% of the total enzyme activity. The % transferase activity (i.e. the transferase activity as a percentage of the total enzymatic activity) may be determined by the following the “Assay for Transferase Activity” given above.
In some aspects of the present invention, the term “without substantially increasing free fatty acids” as used herein means that the amount of free fatty acid in a edible oil treated with an lipid acyltransferase according to the present invention is less than the amount of free fatty acid produced in the edible oil when an enzyme other than a lipid acyltransferase according to the present invention had been used, such as for example as compared with the amount of free fatty acid produced when a conventional phospholipase enzyme, e.g. Lecitase UltraTM (Novozymes A/S, Denmark), had been used.
The term ‘milk’ as used herein may comprise milk from either animal or vegetable origin. It is possible to use milk from animal sources such as buffalo, (traditional) cow, sheep, goat etc. either individually or combined. Vegetable milks such as soya milk may also be used, normally in combination with the animal milk, typically at a low percentage (of vegetable milk) say below 15%, or below 20%, or below 25% v/v. The term milk preferably does not comprise cheese milk and cream.
The term ‘essentially consists’ as used herein, when referring to a product or composition, preferably means that the product or composition, may consist of other products or compositions but only to a maximum concentration of, preferably 10%, such as 5%, such as 3%, such as 2% or 1%, or 0.5% or 0.1%.
For the enzyme modification of milk and/or cream for example it may be preferable to use a temperature of less than about 30° C. for example, suitably less than 20° C. for example, suitably less than 10° C. for example. Suitable temperatures of between 1-30° C. may be used, such as between 3-20° C. for example, such as between 1-10° C.
The enzyme according to the present invention may be used with one or more other suitable food grade enzymes. Thus, it is within the scope of the present invention that, in addition to the enzyme of the invention, at least one further enzyme is added to the foodstuff Such further enzymes include starch degrading enzymes such as endo- or exoamylases, pullulanases, debranching enzymes, hemicellulases including xylanases, cellulases, oxidoreductases, e.g. peroxidases, phenol oxidases, glucose oxidase, pyranose oxidase, sulfhydryl oxidase, or a carbohydrate oxidase such as one which oxidises maltose, for example hexose oxidase (HOX), lipases, phospholipases, glycolipases, galactolipases and proteases.
In one embodiment the enzyme may be Dairy HOXTM, which acts as an oxygen scavenger to prolong shelf life of cheese while providing browning control in pizza ovens. Therefore in a one aspect the present invention relates to the use of an enzyme capable of reducing the maillard reaction in a foodstuff (see WO02/39828 incorporated herein by reference), such as a dairy product, for example cheese, wherein the enzyme is preferably a maltose oxidising enzyme such as carbohydrate oxidase, glucose oxidase and/or hexose oxidase, in the process or preparing a food material and/or foodstuff according to the present invention.
In one preferred embodiment the lipid acyltransferase is used in combination with a lipase having one or more of the following lipase activities: glycolipase activity (E.C. 3.1.1.26, triacylglycerol lipase activity (E.C. 3.1.1.3), phospholipase A2 activity (E.C. 3.1.1.4) or phospholipase A1 activity (E.C. 3.1.1.32). Suitably, lipolytice enzymes are well know within the art and include by way of example the following lipolytic enzymes: LIPOPAN® F and/or LECITASE® ULTRA (Novozymes A/S, Denmark), phospholipase A2 (e.g. phospholipase A2 from LIPOMODTM 22L from Biocatalysts, LIPOMAXTM from Genecor), LIPOLASE® (Novozymes A/S, Denmark), the lipases taught in WO03/97835, EP 0 977 869 or EP 1 193 314. This combination of a lipid acyl transferase as defined herein and a lipase may be particularly preferred in dough or baked products or in fine food products such as cakes and confectionary.
In some embodiments, it may also be beneficial to combine the use of lipid acyltransferase with a lipolytic enzymes such as rennet paste prepared from calf, lamb, kid stomachs, or Palatase A750L (Novo), Palatase M200L (Novo), Palatase M1000 (Novo), or Piccantase A (DSM), also Piccantase from animal sources from DSM (K, KL, L & C) or Lipomod 187, Lipomod 338 (Biocatalysts). These lipases are used conventionally in the production of cheese to produce cheese flavours. These lipases may also be used to produce an enzymatically-modified foodstuff, for example a dairy product (e.g. cheese), particularly where said dairy product consists of, is produced from or comprises butterfat. A combination of the lipid acyltransferase with one or more of these lipases may have a beneficial effect on flavour in the dairy product (e.g. cheese for instance).
The use of lipases in combination with the enzyme of the invention may be particularly advantageous in instances where some accumulation of free fatty acids maybe desirable, for example in cheese where the free fatty acids can impart a desirable flavour, or in the preparation of fine foods. The person skilled in the art will be able to combine proportions of lipolytic enzymes, for example LIPOPAN® F and/or LECITASE® ULTRA (Novozymes A/S, Denmark), phospholipase A2 (e.g. phospholipase A2 from LIPOMODTM 22L from Biocatalysts, LIPOMAXTM from Genecor), LIPOLASE® (Novozymes A/S, Denmark), the lipases taught in WO03/97835, EP 0 977 869 or EP 1 193,314 and the lipid acyltransferase of the present invention to provide the desired ratio of hydrolytic to transferase activity which results in a preferred technical effect or combination of technical effects in the foodstuff (such as those listed herein under ‘Technical Effects’).
It may also be beneficial to combine the use of lipid acyltransferase with a phospholipase, such as phospholipase A1, phospholipase A2, phospholipase B, Phospholipase C and/or phospholipase D.
The combined use may be performed sequentially or concurrently, e.g. the lipid acyl transferase treatment may occur prior to or during the further enzyme treatment. Alternatively, the further enzyme treatment may occur prior to or during the lipid acyl transferase treatment.
In the case of sequential enzyme treatments, in some embodiments it may be advantageous to remove the first enzyme used, e.g. by heat deactivation or by use of an immobilised enzyme, prior to treatment with the second (and/or third etc.) enzyme.
Post-Transcription and Post-Translational Modifications
Suitably the lipid acyltransferase in accordance with the present invention may be encoded by any one of the nucleotide sequences taught herein.
Depending upon the host cell used post-transcriptional and/or post-translational modifications may be made. It is envisaged that the lipid acyltransferase for use in the present methods and/or uses encompasses lipid acyltransferases which have undergone post-transcriptional and/or post-translational modification.
By way of example only, the expression of the nucleotide sequence shown herein as SEQ ID NO: 49 (see FIG. 57) in a host cell (such as Bacillus licheniformis for example) results in post-transcriptional and/or post-translational modifications which lead to the amino acid sequence shown herein as SEQ ID NO: 68 (see FIG. 73).
SEQ ID No. 68 is the same as SEQ ID NO: 16 (shown herein in FIG. 1) except that SEQ ID NO: 68 has undergone post-translational and/or post-transcriptional modification to remove 38 amino acids.
Isolated
In one aspect, the lipid acyltransferase is a recovered/isolated lipid acyltransferase. Thus, the lipid acyltransferase produced may be in an isolated form.
In another aspect, the nucleotide sequence encoding a lipid acyltransferase for use in the present invention may be in an isolated form.
The term “isolated” means that the sequence or protein is at least substantially free from at least one other component with which the sequence or protein is naturally associated in nature and as found in nature.
Purified
In one aspect, the lipid acyltransferase may be in a purified form.
In another aspect, the nucleotide sequence encoding a lipid acyltransferase for use in the present invention may be in a purified form.
The term “purified” means that the sequence is in a relatively pure state—e.g. at least about 51% pure, or at least about 75%, or at least about 80%, or at least about 90% pure, or at least about 95% pure or at least about 98% pure.
Cloning a Nucleotide Sequence Encoding a Polypeptide According to the Present Invention
A nucleotide sequence encoding either a polypeptide which has the specific properties as defined herein or a polypeptide which is suitable for modification may be isolated from any cell or organism producing said polypeptide. Various methods are well known within the art for the isolation of nucleotide sequences.
For example, a genomic DNA and/or cDNA library may be constructed using chromosomal DNA or messenger RNA from the organism producing the polypeptide. If the amino acid sequence of the polypeptide is known, labeled oligonucleotide probes may be synthesised and used to identify polypeptide-encoding clones from the genomic library prepared from the organism. Alternatively, a labelled oligonucleotide probe containing sequences homologous to another known polypeptide gene could be used to identify polypeptide-encoding clones. In the latter case, hybridisation and washing conditions of lower stringency are used.
Alternatively, polypeptide-encoding clones could be identified by inserting fragments of genomic DNA into an expression vector, such as a plasmid, transforming enzyme-negative bacteria with the resulting genomic DNA library, and then plating the transformed bacteria onto agar containing an enzyme inhibited by the polypeptide, thereby allowing clones expressing the polypeptide to be identified.
In a yet further alternative, the nucleotide sequence encoding the polypeptide may be prepared synthetically by established standard methods, e.g. the phosphoroamidite method described by Beucage S. L. et al (1981) Tetrahedron Letters 22, p 1859-1869, or the method described by Matthes et al (1984) EMBO J. 3, p 801-805. In the phosphoroamidite method, oligonucleotides are synthesised, e.g. in an automatic DNA synthesiser, purified, annealed, ligated and cloned in appropriate vectors.
The nucleotide sequence may be of mixed genomic and synthetic origin, mixed synthetic and cDNA origin, or mixed genomic and cDNA origin, prepared by ligating fragments of synthetic, genomic or cDNA origin (as appropriate) in accordance with standard techniques. Each ligated fragment corresponds to various parts of the entire nucleotide sequence. The DNA sequence may also be prepared by polymerase chain reaction (PCR) using specific primers, for instance as described in U.S. Pat. No. 4,683,202 or in Saiki R K et al (Science (1988) 239, pp 487-491).
Nucleotide Sequences
The present invention also encompasses nucleotide sequences encoding polypeptides having the specific properties as defined herein. The term “nucleotide sequence” as used herein refers to an oligonucleotide sequence or polynucleotide sequence, and variant, homologues, fragments and derivatives thereof (such as portions thereof). The nucleotide sequence may be of genomic or synthetic or recombinant origin, which may be double-stranded or single-stranded whether representing the sense or antisense strand.
The term “nucleotide sequence” in relation to the present invention includes genomic DNA, cDNA, synthetic DNA, and RNA. Preferably it means DNA, more preferably cDNA for the coding sequence.
In a preferred embodiment, the nucleotide sequence per se encoding a polypeptide having the specific properties as defined herein does not cover the native nucleotide sequence in its natural environment when it is linked to its naturally associated sequence(s) that is/are also in its/their natural environment. For ease of reference, we shall call this preferred embodiment the “non-native nucleotide sequence”. In this regard, the term “native nucleotide sequence” means an entire nucleotide sequence that is in its native environment and when operatively linked to an entire promoter with which it is naturally associated, which promoter is also in its native environment. Thus, the polypeptide of the present invention can be expressed by a nucleotide sequence in its native organism but wherein the nucleotide sequence is not under the control of the promoter with which it is naturally associated within that organism.
Preferably the polypeptide is not a native polypeptide. In this regard, the term “native polypeptide” means an entire polypeptide that is in its native environment and when it has been expressed by its native nucleotide sequence.
Typically, the nucleotide sequence encoding polypeptides having the specific properties as defined herein is prepared using recombinant DNA techniques (i.e. recombinant DNA). However, in an alternative embodiment of the invention, the nucleotide sequence could be synthesised, in whole or in part, using chemical methods well known in the art (see Caruthers M H et al (1980) Nuc Acids Res Symp Ser 215-23 and Horn T et al (1980) Nuc Acids Res Symp Ser 225-232).
Molecular Evolution
Once an enzyme-encoding nucleotide sequence has been isolated, or a putative enzyme-encoding nucleotide sequence has been identified, it may be desirable to modify the selected nucleotide sequence, for example it may be desirable to mutate the sequence in order to prepare an enzyme in accordance with the present invention.
Mutations may be introduced using synthetic oligonucleotides. These oligonucleotides contain nucleotide sequences flanking the desired mutation sites.
A suitable method is disclosed in Morinaga et al (Biotechnology (1984) 2, p 646-649). Another method of introducing mutations into enzyme-encoding nucleotide sequences is described in Nelson and Long (Analytical Biochemistry (1989), 180, p 147-151).
Instead of site directed mutagenesis, such as described above, one can introduce mutations randomly for instance using a commercial kit such as the GeneMorph PCR mutagenesis kit from Stratagene, or the Diversify PCR random mutagenesis kit from Clontech. EP 0 583 265 refers to methods of optimising PCR based mutagenesis, which can also be combined with the use of mutagenic DNA analogues such as those described in EP 0 866 796. Error prone PCR technologies are suitable for the production of variants of lipid acyl transferases with preferred characteristics. WO0206457 refers to molecular evolution of lipases.
A third method to obtain novel sequences is to fragment non-identical nucleotide sequences, either by using any number of restriction enzymes or an enzyme such as Dnase I, and reassembling full nucleotide sequences coding for functional proteins. Alternatively one can use one or multiple non-identical nucleotide sequences and introduce mutations during the reassembly of the full nucleotide sequence. DNA shuffling and family shuffling technologies are suitable for the production of variants of lipid acyl transferases with preferred characteristics. Suitable methods for performing ‘shuffling’ can be found in EP0 752 008, EP1 138 763, EP1 103 606. Shuffling can also be combined with other forms of DNA mutagenesis as described in U.S. Pat. No. 6,180,406 and WO 01/34835.
Thus, it is possible to produce numerous site directed or random mutations into a nucleotide sequence, either in vivo or in vitro, and to subsequently screen for improved functionality of the encoded polypeptide by various means. Using in silico and exo mediated recombination methods (see WO 00/58517, U.S. Pat. No. 6,344,328, U.S. Pat. No. 6,361,974), for example, molecular evolution can be performed where the variant produced retains very low homology to known enzymes or proteins. Such variants thereby obtained may have significant structural analogy to known transferase enzymes, but have very low amino acid sequence homology.
As a non-limiting example, In addition, mutations or natural variants of a polynucleotide sequence can be recombined with either the wild type or other mutations or natural variants to produce new variants. Such new variants can also be screened for improved functionality of the encoded polypeptide.
The application of the above-mentioned and similar molecular evolution methods allows the identification and selection of variants of the enzymes of the present invention which have preferred characteristics without any prior knowledge of protein structure or function, and allows the production of non-predictable but beneficial mutations or variants. There are numerous examples of the application of molecular evolution in the art for the optimisation or alteration of enzyme activity, such examples include, but are not limited to one or more of the following: optimised expression and/or activity in a host cell or in vitro, increased enzymatic activity, altered substrate and/or product specificity, increased or decreased enzymatic or structural stability, altered enzymatic activity/specificity in preferred environmental conditions, e.g. temperature, pH, substrate
As will be apparent to a person skilled in the art, using molecular evolution tools an enzyme may be altered to improve the functionality of the enzyme.
Suitably, the nucleotide sequence encoding a lipid acyltransferase used in the invention may encode a variant lipid acyltransferase, i.e. the lipid acyltransferase may contain at least one amino acid substitution, deletion or addition, when compared to a parental enzyme. Variant enzymes retain at least 1%, 2%, 3%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 97%, 99% homology with the parent enzyme. Suitable parent enzymes may include any enzyme with esterase or lipase activity. Preferably, the parent enzyme aligns to the pfam00657 consensus sequence.
In a preferable embodiment a variant lipid acyltransferase enzyme retains or incorporates at least one or more of the pfam00657 consensus sequence amino acid residues found in the GDSX (SEQ ID NO: 120), GANDY (SEQ ID NO: 118) and HPT blocks.
Enzymes, such as lipases with no or low lipid acyltransferase activity in an aqueous environment may be mutated using molecular evolution tools to introduce or enhance the transferase activity, thereby producing a lipid acyltransferase enzyme with significant transferase activity suitable for use in the compositions and methods of the present invention.
Suitably, the nucleotide sequence encoding a lipid acyltransferase for use in any one of the methods and/or uses of the present invention may encode a lipid acyltransferase that may be a variant with enhanced enzyme activity on polar lipids, preferably phospholipids and/or glycolipids when compared to the parent enzyme. Preferably, such variants also have low or no activity on lyso polar lipids. The enhanced activity on polar lipids, phospholipids and/or glycolipids may be the result of hydrolysis and/or transferase activity or a combination of both.
Variant lipid acyltransferases may have decreased activity on triglycerides, and/or monoglycerides and/or diglycerides compared with the parent enzyme.
Suitably the variant enzyme may have no activity on triglycerides and/or monoglycerides and/or diglycerides.
Alternatively, the variant enzyme may have increased activity on triglycerides, and/or may also have increased activity on one or more of the following, polar lipids, phospholipids, lecithin, phosphatidylcholine, glycolipids, digalactosyl monoglyceride, monogalactosyl monoglyceride.
Variants of lipid acyltransferases are known, and one or more of such variants may be suitable for use in the methods and uses according to the present invention and/or in the enzyme compositions according to the present invention. By way of example only, variants of lipid acyltransferases are described in the following references may be used in accordance with the present invention: Hilton & Buckley J. Biol. Chem. 1991 Jan. 15: 266 (2): 997-1000; Robertson et al J. Biol. Chem. 1994 Jan. 21; 269(3):2146-50; Brumlik et al J. Bacteriol 1996 April; 178 (7): 2060-4; Peelman et al Protein Sci. 1998 March; 7(3):587-99.
Amino Acid Sequences
The present invention also encompasses the use of amino acid sequences encoded by a nucleotide sequence which encodes a lipid acyltransferase for use in any one of the methods and/or uses of the present invention.
As used herein, the term “amino acid sequence” is synonymous with the term “polypeptide” and/or the term “protein”. In some instances, the term “amino acid sequence” is synonymous with the term “peptide”.
The amino acid sequence may be prepared/isolated from a suitable source, or it may be made synthetically or it may be prepared by use of recombinant DNA techniques.
Suitably, the amino acid sequences may be obtained from the isolated polypeptides taught herein by standard techniques.
One suitable method for determining amino acid sequences from isolated polypeptides is as follows:
Purified polypeptide may be freeze-dried and 100 μg of the freeze-dried material may be dissolved in 50 μl of a mixture of 8 M urea and 0.4 M ammonium hydrogen carbonate, pH 8.4. The dissolved protein may be denatured and reduced for 15 minutes at 50° C. following overlay with nitrogen and addition of 5 μl of 45 mM dithiothreitol. After cooling to room temperature, 5 μl of 100 mM iodoacetamide may be added for the cysteine residues to be derivatized for 15 minutes at room temperature in the dark under nitrogen. 135 μl of water and 5 μg of endoproteinase Lys-C in 5 μl of water may be added to the above reaction mixture and the digestion may be carried out at 37° C. under nitrogen for 24 hours. The resulting peptides may be separated by reverse phase HPLC on a VYDAC C18 column (0.46×15 cm; 10 μm; The Separation Group, California, USA) using solvent A: 0.1% TFA in water and solvent B: 0.1% TFA in acetonitrile. Selected peptides may be re-chromatographed on a Develosil C18 column using the same solvent system, prior to N-terminal sequencing. Sequencing may be done using an Applied Biosystems 476A sequencer using pulsed liquid fast cycles according to the manufacturer's instructions (Applied Biosystems, California, USA).

Sequence Identity or Sequence Homology

Here, the term “homologue” means an entity having a certain homology with the subject amino acid sequences and the subject nucleotide sequences. Here, the term “homology” can be equated with “identity”.
The homologous amino acid sequence and/or nucleotide sequence should provide and/or encode a polypeptide which retains the functional activity and/or enhances the activity of the enzyme.
In the present context, a homologous sequence is taken to include an amino acid sequence which may be at least 75, 85 or 90% identical, preferably at least 95 or 98% identical to the subject sequence. Typically, the homologues will comprise the same active sites etc. as the subject amino acid sequence. Although homology can also be considered in terms of similarity (i.e. amino acid residues having similar chemical properties/functions), in the context of the present invention it is preferred to express homology in terms of sequence identity.
In the present context, a homologous sequence is taken to include a nucleotide sequence which may be at least 75, 85 or 90% identical, preferably at least 95 or 98% identical to a nucleotide sequence encoding a polypeptide of the present invention (the subject sequence). Typically, the homologues will comprise the same sequences that code for the active sites etc. as the subject sequence. Although homology can also be considered in terms of similarity (i.e. amino acid residues having similar chemical properties/functions), in the context of the present invention it is preferred to express homology in terms of sequence identity.
Homology comparisons can be conducted by eye, or more usually, with the aid of readily available sequence comparison programs. These commercially available computer programs can calculate % homology between two or more sequences.
% homology may be calculated over contiguous sequences, i.e. one sequence is aligned with the other sequence and each amino acid in one sequence is directly compared with the corresponding amino acid in the other sequence, one residue at a time. This is called an “ungapped” alignment. Typically, such ungapped alignments are performed only over a relatively short number of residues.
Although this is a very simple and consistent method, it fails to take into consideration that, for example, in an otherwise identical pair of sequences, one insertion or deletion will cause the following amino acid residues to be put out of alignment, thus potentially resulting in a large reduction in % homology when a global alignment is performed. Consequently, most sequence comparison methods are designed to produce optimal alignments that take into consideration possible insertions and deletions without penalising unduly the overall homology score. This is achieved by inserting “gaps” in the sequence alignment to try to maximise local homology.
However, these more complex methods assign “gap penalties” to each gap that occurs in the alignment so that, for the same number of identical amino acids, a sequence alignment with as few gaps as possible—reflecting higher relatedness between the two compared sequences—will achieve a higher score than one with many gaps. “Affine gap costs” are typically used that charge a relatively high cost for the existence of a gap and a smaller penalty for each subsequent residue in the gap. This is the most commonly used gap scoring system. High gap penalties will of course produce optimised alignments with fewer gaps. Most alignment programs allow the gap penalties to be modified. However, it is preferred to use the default values when using such software for sequence comparisons.
Calculation of maximum % homology therefore firstly requires the production of an optimal alignment, taking into consideration gap penalties. A suitable computer program for carrying out such an alignment is the Vector NTI (Invitrogen Corp.). Examples of other software that can perform sequence comparisons include, but are not limited to, the BLASTTMpackage (see Ausubel et al 1999 Short Protocols in Molecular Biology, 4.sup.th Ed—Chapter 18), and FASTA (Altschul et al 1990 J. Mol. Biol. 403-410). Both BLASTTM and FASTA are available for offline and online searching (see Ausubel et al 1999, pages 7-58 to 7-60). However, for some applications, it is preferred to use the Vector NTI program. A new tool, called BLAST 2 Sequences is also available for comparing protein and nucleotide sequence (see FEMS Microbiol Lett 1999 174(2): 247-50; FEMS Microbiol Lett 1999 177(1): 187-8).
Although the final % homology can be measured in terms of identity, the alignment process itself is typically not based on an all-or-nothing pair comparison. Instead, a scaled similarity score matrix is generally used that assigns scores to each pairwise comparison based on chemical similarity or evolutionary distance. An example of such a matrix commonly used is the BLOSUM62 matrix—the default matrix for the BLASTTM suite of programs. Vector NTI programs generally use either the public default values or a custom symbol comparison table if supplied (see user manual for further details). For some applications, it is preferred to use the default values for the Vector NTI package.
Alternatively, percentage homologies may be calculated using the multiple alignment feature in Vector NTI (Invitrogen Corp.), based on an algorithm, analogous to CLUSTAL (Higgins D G & Sharp P M (1988), Gene 73(1), 237-244).
Once the software has produced an optimal alignment, it is possible to calculate % homology, preferably % sequence identity. The software typically does this as part of the sequence comparison and generates a numerical result.
Should Gap Penalties be used when determining sequence identity, then preferably the following parameters are used for pairwise alignment:












FOR BLAST TM


















GAP OPEN
0



GAP EXTENSION
0
























FOR CLUSTAL
DNA
PROTEIN





















WORD SIZE
2
1
K triple



GAP PENALTY
15
10




GAP EXTENSION
6.66
0.1









In one embodiment, preferably the sequence identity for the nucleotide sequences is determined using CLUSTAL with the gap penalty and gap extension set as defined above.
Suitably, the degree of identity with regard to a nucleotide sequence is determined over at least 20 contiguous nucleotides, preferably over at least 30 contiguous nucleotides, preferably over at least 40 contiguous nucleotides, preferably over at least 50 contiguous nucleotides, preferably over at least 60 contiguous nucleotides, preferably over at least 100 contiguous nucleotides.
Suitably, the degree of identity with regard to a nucleotide sequence may be determined over the whole sequence.
In one embodiment the degree of amino acid sequence identity in accordance with the present invention may be suitably determined by means of computer programs known in the art, such as Vector NTI 10 (Invitrogen Corp.). For pairwise alignment the matrix used is preferably BLOSUM62 with Gap opening penalty of 10.0 and Gap extension penalty of 0.1.
Suitably, the degree of identity with regard to an amino acid sequence is determined over at least 20 contiguous amino acids, preferably over at least 30 contiguous amino acids, preferably over at least 40 contiguous amino acids, preferably over at least 50 contiguous amino acids, preferably over at least 60 contiguous amino acids.
Suitably, the degree of identity with regard to an amino acid sequence may be determined over the whole sequence.
The sequences may also have deletions, insertions or substitutions of amino acid residues which produce a silent change and result in a functionally equivalent substance. Deliberate amino acid substitutions may be made on the basis of similarity in polarity, charge, solubility, hydrophobicity, hydrophilicity, and/or the amphipathic nature of the residues as long as the secondary binding activity of the substance is retained. For example, negatively charged amino acids include aspartic acid and glutamic acid; positively charged amino acids include lysine and arginine; and amino acids with uncharged polar head groups having similar hydrophilicity values include leucine, isoleucine, valine, glycine, alanine, asparagine, glutamine, serine, threonine, phenylalanine, and tyrosine.
Conservative substitutions may be made, for example according to the Table below. Amino acids in the same block in the second column and preferably in the same line in the third column may be substituted for each other:
















ALIPHATIC
Non-polar
G A P





I L V




Polar - uncharged
C S T M





N Q




Polar - charged
D E





K R



AROMATIC

H F W Y









The present invention also encompasses homologous substitution (substitution and replacement are both used herein to mean the interchange of an existing amino acid residue, with an alternative residue) that may occur i.e. like-for-like substitution such as basic for basic, acidic for acidic, polar for polar etc. Non-homologous substitution may also occur i.e. from one class of residue to another or alternatively involving the inclusion of unnatural amino acids such as ornithine (hereinafter referred to as Z), diaminobutyric acid ornithine (hereinafter referred to as B), norleucine ornithine (hereinafter referred to as O), pyriylalanine, thienylalanine, naphthylalanine and phenylglycine.
Replacements may also be made by unnatural amino acids.
Variant amino acid sequences may include suitable spacer groups that may be inserted between any two amino acid residues of the sequence including alkyl groups such as methyl, ethyl or propyl groups in addition to amino acid spacers such as glycine or β-alanine residues. A further form of variation, involves the presence of one or more amino acid residues in peptoid form, will be well understood by those skilled in the art. For the avoidance of doubt, “the peptoid form” is used to refer to variant amino acid residues wherein the α-carbon substituent group is on the residue's nitrogen atom rather than the α-carbon. Processes for preparing peptides in the peptoid form are known in the art, for example Simon R J et al., PNAS (1992) 89(20), 9367-9371 and Horwell D C, Trends Biotechnol. (1995) 13(4), 132-134.
Nucleotide sequences for use in the present invention or encoding a polypeptide having the specific properties defined herein may include within them synthetic or modified nucleotides. A number of different types of modification to oligonucleotides are known in the art. These include methylphosphonate and phosphorothioate backbones and/or the addition of acridine or polylysine chains at the 3′ and/or 5′ ends of the molecule. For the purposes of the present invention, it is to be understood that the nucleotide sequences described herein may be modified by any method available in the art. Such modifications may be carried out in order to enhance the in vivo activity or life span of nucleotide sequences.
The present invention also encompasses the use of nucleotide sequences that are complementary to the sequences discussed herein, or any derivative, fragment or derivative thereof. If the sequence is complementary to a fragment thereof then that sequence can be used as a probe to identify similar coding sequences in other organisms etc.
Polynucleotides which are not 100% homologous to the sequences of the present invention but fall within the scope of the invention can be obtained in a number of ways. Other variants of the sequences described herein may be obtained for example by probing DNA libraries made from a range of individuals, for example individuals from different populations. In addition, other viral/bacterial, or cellular homologues particularly cellular homologues found in mammalian cells (e.g. rat, mouse, bovine and primate cells), may be obtained and such homologues and fragments thereof in general will be capable of selectively hybridising to the sequences shown in the sequence listing herein. Such sequences may be obtained by probing cDNA libraries made from or genomic DNA libraries from other animal species, and probing such libraries with probes comprising all or part of any one of the sequences in the attached sequence listings under conditions of medium to high stringency. Similar considerations apply to obtaining species homologues and allelic variants of the polypeptide or nucleotide sequences of the invention.
Variants and strain/species homologues may also be obtained using degenerate PCR which will use primers designed to target sequences within the variants and homologues encoding conserved amino acid sequences within the sequences of the present invention. Conserved sequences can be predicted, for example, by aligning the amino acid sequences from several variants/homologues. Sequence alignments can be performed using computer software known in the art. For example the GCG Wisconsin PileUp program is widely used.
The primers used in degenerate PCR will contain one or more degenerate positions and will be used at stringency conditions lower than those used for cloning sequences with single sequence primers against known sequences.
Alternatively, such polynucleotides may be obtained by site directed mutagenesis of characterised sequences. This may be useful where for example silent codon sequence changes are required to optimise codon preferences for a particular host cell in which the polynucleotide sequences are being expressed. Other sequence changes may be desired in order to introduce restriction polypeptide recognition sites, or to alter the property or function of the polypeptides encoded by the polynucleotides.
Polynucleotides (nucleotide sequences) of the invention may be used to produce a primer, e.g. a PCR primer, a primer for an alternative amplification reaction, a probe e.g. labelled with a revealing label by conventional means using radioactive or non-radioactive labels, or the polynucleotides may be cloned into vectors. Such primers, probes and other fragments will be at least 15, preferably at least 20, for example at least 25, 30 or 40 nucleotides in length, and are also encompassed by the term polynucleotides of the invention as used herein.
Polynucleotides such as DNA polynucleotides and probes according to the invention may be produced recombinantly, synthetically, or by any means available to those of skill in the art. They may also be cloned by standard techniques.
In general, primers will be produced by synthetic means, involving a stepwise manufacture of the desired nucleic acid sequence one nucleotide at a time. Techniques for accomplishing this using automated techniques are readily available in the art.
Longer polynucleotides will generally be produced using recombinant means, for example using a PCR (polymerase chain reaction) cloning techniques. This will involve making a pair of primers (e.g. of about 15 to 30 nucleotides) flanking a region of the lipid targeting sequence which it is desired to clone, bringing the primers into contact with mRNA or cDNA obtained from an animal or human cell, performing a polymerase chain reaction under conditions which bring about amplification of the desired region, isolating the amplified fragment (e.g. by purifying the reaction mixture on an agarose gel) and recovering the amplified DNA. The primers may be designed to contain suitable restriction enzyme recognition sites so that the amplified DNA can be cloned into a suitable cloning vector.
Hybridisation
The present invention also encompasses the use of sequences that are complementary to the sequences of the present invention or sequences that are capable of hybridising either to the sequences of the present invention or to sequences that are complementary thereto.
The term “hybridisation” as used herein shall include “the process by which a strand of nucleic acid joins with a complementary strand through base pairing” as well as the process of amplification as carried out in polymerase chain reaction (PCR) technologies.
The present invention also encompasses the use of nucleotide sequences that are capable of hybridising to the sequences that are complementary to the subject sequences discussed herein, or any derivative, fragment or derivative thereof.
The present invention also encompasses sequences that are complementary to sequences that are capable of hybridising to the nucleotide sequences discussed herein.
Hybridisation conditions are based on the melting temperature (Tm) of the nucleotide binding complex, as taught in Berger and Kimmel (1987, Guide to Molecular Cloning Techniques, Methods in Enzymology, Vol. 152, Academic Press, San Diego Calif.), and confer a defined “stringency” as explained below.
Maximum stringency typically occurs at about Tm−5° C. (5° C. below the Tm of the probe); high stringency at about 5° C. to 10° C. below Tm; intermediate stringency at about 10° C. to 20° C. below Tm; and low stringency at about 20° C. to 25° C. below Tm. As will be understood by those of skill in the art, a maximum stringency hybridisation can be used to identify or detect identical nucleotide sequences while an intermediate (or low) stringency hybridisation can be used to identify or detect similar or related polynucleotide sequences.
Preferably, the present invention encompasses the use of sequences that are complementary to sequences that are capable of hybridising under high stringency conditions or intermediate stringency conditions to nucleotide sequences encoding polypeptides having the specific properties as defined herein.
More preferably, the present invention encompasses the use of sequences that are complementary to sequences that are capable of hybridising under high stringency conditions (e.g. 65° C. and 0.1×SSC {1×SSC=0.15 M NaCl, 0.015 M Na-citrate pH 7.0}) to nucleotide sequences encoding polypeptides having the specific properties as defined herein.
The present invention also relates to the use of nucleotide sequences that can hybridise to the nucleotide sequences discussed herein (including complementary sequences of those discussed herein).
The present invention also relates to the use of nucleotide sequences that are complementary to sequences that can hybridise to the nucleotide sequences discussed herein (including complementary sequences of those discussed herein).
Also included within the scope of the present invention are the use of polynucleotide sequences that are capable of hybridising to the nucleotide sequences discussed herein under conditions of intermediate to maximal stringency.
In a preferred aspect, the present invention covers the use of nucleotide sequences that can hybridise to the nucleotide sequences discussed herein, or the complement thereof, under stringent conditions (e.g. 50° C. and 0.2×SSC).
In a more preferred aspect, the present invention covers the use of nucleotide sequences that can hybridise to the nucleotide sequences discussed herein, or the complement thereof, under high stringency conditions (e.g. 65° C. and 0.1×SSC).
Expression of Polypeptides
A nucleotide sequence for use in the present invention or for encoding a polypeptide having the specific properties as defined herein can be incorporated into a recombinant replicable vector. The vector may be used to replicate and express the nucleotide sequence, in polypeptide form, in and/or from a compatible host cell. Expression may be controlled using control sequences which include promoters/enhancers and other expression regulation signals. Prokaryotic promoters and promoters functional in eukaryotic cells may be used. Tissue specific or stimuli specific promoters may be used. Chimeric promoters may also be used comprising sequence elements from two or more different promoters described above.
The polypeptide produced by a host recombinant cell by expression of the nucleotide sequence may be secreted or may be contained intracellularly depending on the sequence and/or the vector used. The coding sequences can be designed with signal sequences which direct secretion of the substance coding sequences through a particular prokaryotic or eukaryotic cell membrane.
Constructs
The term “construct”—which is synonymous with terms such as “conjugate”, “cassette” and “hybrid”—includes a nucleotide sequence encoding a polypeptide having the specific properties as defined herein for use according to the present invention directly or indirectly attached to a promoter. An example of an indirect attachment is the provision of a suitable spacer group such as an intron sequence, such as the Sh1-intron or the ADH intron, intermediate the promoter and the nucleotide sequence of the present invention. The same is true for the term “fused” in relation to the present invention which includes direct or indirect attachment. In some cases, the terms do not cover the natural combination of the nucleotide sequence coding for the protein ordinarily associated with the wild type gene promoter and when they are both in their natural environment.
The construct may even contain or express a marker which allows for the selection of the genetic construct.
For some applications, preferably the construct comprises at least a nucleotide sequence of the present invention or a nucleotide sequence encoding a polypeptide having the specific properties as defined herein operably linked to a promoter.
Organism
The term “organism” in relation to the present invention includes any organism that could comprise a nucleotide sequence according to the present invention or a nucleotide sequence encoding for a polypeptide having the specific properties as defined herein and/or products obtained therefrom.
The term “transgenic organism” in relation to the present invention includes any organism that comprises a nucleotide sequence coding for a polypeptide having the specific properties as defined herein and/or the products obtained therefrom, and/or wherein a promoter can allow expression of the nucleotide sequence coding for a polypeptide having the specific properties as defined herein within the organism. Preferably the nucleotide sequence is incorporated in the genome of the organism.
The term “transgenic organism” does not cover native nucleotide coding sequences in their natural environment when they are under the control of their native promoter which is also in its natural environment.
Therefore, the transgenic organism of the present invention includes an organism comprising any one of, or combinations of, a nucleotide sequence coding for a polypeptide having the specific properties as defined herein, constructs as defined herein, vectors as defined herein, plasmids as defined herein, cells as defined herein, or the products thereof. For example the transgenic organism can also comprise a nucleotide sequence coding for a polypeptide having the specific properties as defined herein under the control of a promoter not associated with a sequence encoding a lipid acyltransferase in nature.
Transformation of Host Cells/Organism
The host organism can be a prokaryotic or a eukaryotic organism.
Examples of suitable prokaryotic hosts include bacteria such as E. coli and Bacillus licheniformis, preferably B. licheniformis. 
Teachings on the transformation of prokaryotic hosts is well documented in the art, for example see Sambrook et al (Molecular Cloning: A Laboratory Manual, 2nd edition, 1989, Cold Spring Harbor Laboratory Press). If a prokaryotic host is used then the nucleotide sequence may need to be suitably modified before transformation—such as by removal of introns.
In another embodiment the transgenic organism can be a yeast.
Filamentous fungi cells may be transformed using various methods known in the art—such as a process involving protoplast formation and transformation of the protoplasts followed by regeneration of the cell wall in a manner known. The use of Aspergillus as a host microorganism is described in EP 0 238 023.
Another host organism can be a plant. A review of the general techniques used for transforming plants may be found in articles by Potrykus (Annu Rev Plant Physiol Plant Mol Biol [1991] 42:205-225) and Christou (Agro-Food-Industry Hi-Tech March/April 1994 17-27). Further teachings on plant transformation may be found in EP-A-0449375.
General teachings on the transformation of fungi, yeasts and plants are presented in following sections.
Transformed Fungus
A host organism may be a fungus—such as a filamentous fungus. Examples of suitable such hosts include any member belonging to the genera Thermomyces, Acremonium, Aspergillus, Penicillium, Mucor, Neurospora, Trichoderma and the like.
Methods referred to on transforming filamentous fungi are reviewed in U.S. Pat. No. 5,741,665 which states that standard techniques for transformation of filamentous fungi and culturing the fungi are well known in the art. An extensive review of techniques as applied to N crassa is found, for example in Davis and de Serres, Methods Enzymol (1971) 17A: 79-143.
Further teachings on transforming filamentous fungi are reviewed in U.S. Pat. No. 5,674,707.
In one aspect, the host organism can be of the genus Aspergillus, such as Aspergillus niger. 
A transgenic Aspergillus according to the present invention can also be prepared by following, for example, referred to in Turner G. 1994 (Vectors for genetic manipulation. In: Martinelli S. D., Kinghorn J. R. (Editors) Aspergillus: 50 years on. Progress in industrial microbiology vol 29. Elsevier Amsterdam 1994. pp. 641-666).
Gene expression in filamentous fungi has been reviewed in Punt et al. (2002) Trends Biotechnol 2002 May; 20(5):200-6, Archer & Peberdy Crit. Rev Biotechnol (1997) 17(4):273-306.
Transformed Yeast
In another embodiment, the transgenic organism can be a yeast.
A review of the principles of heterologous gene expression in yeast are provided in, for example, Methods Mol Biol (1995), 49:341-54, and Curr Opin Biotechnol (1997) October; 8(5):554-60
In this regard, yeast—such as the species Saccharomyces cerevisi or Pichia pastoris (see FEMS Microbiol Rev (2000 24(1):45-66), may be used as a vehicle for heterologous gene expression.
A review of the principles of heterologous gene expression in Saccharomyces cerevisiae and secretion of gene products is given by E Hinchcliffe E Kenny (1993, “Yeast as a vehicle for the expression of heterologous genes”, Yeasts, Vol 5, Anthony H Rose and J Stuart Harrison, eds, 2nd edition, Academic Press Ltd.).
For the transformation of yeast, several transformation protocols have been developed. For example, a transgenic Saccharomyces according to the present invention can be prepared by following the teachings of Hinnen et al., (1978, Proceedings of the National Academy of Sciences of the USA 75, 1929); Beggs, J D (1978, Nature, London, 275, 104); and Ito, H et al (1983, J Bacteriology 153, 163-168).
The transformed yeast cells may be selected using various selective markers—such as auxotrophic markers dominant antibiotic resistance markers.
A suitable yeast host organism can be selected from the biotechnologically relevant yeasts species such as, but not limited to, yeast species selected from Pichia spp., Hansenula spp., Kluyveromyces, Yarrowinia spp., Saccharomyces spp., including S. cerevisiae, or Schizosaccharomyce spp. including Schizosaccharomyce pombe. 
A strain of the methylotrophic yeast species Pichia pastoris may be used as the host organism.
In one embodiment, the host organism may be a Hansenula species, such as H. polymorpha (as described in WO01/39544).
Transformed Plants/Plant Cells
A host organism suitable for the present invention may be a plant. A review of the general techniques may be found in articles by Potrykus (Annu Rev Plant Physiol Plant Mol Biol 42:205-225) and Christou (Agro-Food-Industry Hi-Tech March/April 1994 17-27), or in WO01/16308. The transgenic plant may produce enhanced levels of phytosterol esters and phytostanol esters, for example.
Therefore the present invention also relates to a method for the production of a transgenic plant with enhanced levels of phytosterol esters and phytostanol esters, comprising the steps of transforming a plant cell with a lipid acyltransferase as defined herein (in particular with an expression vector or construct comprising a lipid acyltransferase as defined herein), and growing a plant from the transformed plant cell.
Secretion
Often, it is desirable for the polypeptide to be secreted from the expression host into the culture medium from where the enzyme may be more easily recovered. According to the present invention, the secretion leader sequence may be selected on the basis of the desired expression host. Hybrid signal sequences may also be used with the context of the present invention.
Typical examples of secretion leader sequences not associated with a nucleotide sequence encoding a lipid acyltransferase in nature are those originating from the fungal amyloglucosidase (AG) gene (glaA—both 18 and 24 amino acid versions e.g. from Aspergillus), the α-factor gene (yeasts e.g. Saccharomyces, Kluyveromyces and Hansenula) or the α-amylase gene (Bacillus).
Detection
A variety of protocols for detecting and measuring the expression of the amino acid sequence are known in the art. Examples include enzyme-linked immunosorbent assay (ELISA), radioimmunoassay (RIA) and fluorescent activated cell sorting (FACS).
A wide variety of labels and conjugation techniques are known by those skilled in the art and can be used in various nucleic and amino acid assays.
A number of companies such as Pharmacia Biotech (Piscataway, N.J.), Promega (Madison, Wis.), and US Biochemical Corp (Cleveland, Ohio) supply commercial kits and protocols for these procedures.
Suitable reporter molecules or labels include those radionuclides, enzymes, fluorescent, chemiluminescent, or chromogenic agents as well as substrates, cofactors, inhibitors, magnetic particles and the like. Patents teaching the use of such labels include U.S. Pat. No. 3,817,837; U.S. Pat. No. 3,850,752; U.S. Pat. No. 3,939,350; U.S. Pat. No. 3,996,345; U.S. Pat. No. 4,277,437; U.S. Pat. No. 4,275,149 and U.S. Pat. No. 4,366,241.
Also, recombinant immunoglobulins may be produced as shown in U.S. Pat. No. 4,816,567.
Fusion Proteins
The lipid acyltransferase for use in the present invention may be produced as a fusion protein, for example to aid in extraction and purification thereof. Examples of fusion protein partners include glutathione-S-transferase (GST), 6×His (SEQ ID NO: 136), GAL4 (DNA binding and/or transcriptional activation domains) and β-galactosidase. It may also be convenient to include a proteolytic cleavage site between the fusion protein partner and the protein sequence of interest to allow removal of fusion protein sequences. Preferably the fusion protein will not hinder the activity of the protein sequence.
Gene fusion expression systems in E. coli have been reviewed in Curr. Opin. Biotechnol. (1995) 6(5):501-6.
The amino acid sequence of a polypeptide having the specific properties as defined herein may be ligated to a non-native sequence to encode a fusion protein. For example, for screening of peptide libraries for agents capable of affecting the substance activity, it may be useful to encode a chimeric substance expressing a non-native epitope that is recognised by a commercially available antibody.



BRIEF DESCRIPTION OF THE DRAWINGS
The detailed description, given by way of example, but not intended to limit the invention solely to the specific embodiments described, may best be understood in conjunction with the accompanying drawings, in which:
FIG. 1 shows the amino acid sequence of a mutant Aeromonas salmonicida mature lipid acyltransferase (GCAT) with a mutation of Asn80Asp (notably, amino acid 80 is in the mature sequence) (SEQ ID NO: 16);
FIG. 2 shows an amino acid sequence (SEQ ID NO: 1) a lipid acyl transferase from Aeromonas hydrophila (ATCC #7965);
FIG. 3 shows a pfam00657 consensus sequence from database version 6 (SEQ ID NO: 2);
FIG. 4 shows an amino acid sequence (SEQ ID NO: 3) obtained from the organism Aeromonas hydrophila (P10480; GI:121051);
FIG. 5 shows an amino acid sequence (SEQ ID NO: 4) obtained from the organism Aeromonas salmonicida (AAG098404; GI:9964017);
FIG. 6 shows an amino acid sequence (SEQ ID NO: 5) obtained from the organism Streptomyces coelicolor A3(2) (Genbank accession number NP.sub.—631558);
FIG. 7 shows an amino acid sequence (SEQ ID NO: 6) obtained from the organism Streptomyces coelicolor A3(2) (Genbank accession number: CAC42140);
FIG. 8 shows an amino acid sequence (SEQ ID NO: 7) obtained from the organism Saccharomyces cerevisiae (Genbank accession number P41734);
FIG. 9 shows an amino acid sequence (SEQ ID NO: 8) obtained from the organism Ralstonia (Genbank accession number: AL646052);
FIG. 10 shows SEQ ID NO: 9. Scoe1 NCBI protein accession code CAB39707.1 GI:4539178 conserved hypothetical protein [Streptomyces coelicolor A3(2)];
FIG. 11 shows an amino acid shown as SEQ ID NO: 10. Scoe2 NCBI protein accession code CAC01477.1 GI:9716139 conserved hypothetical protein [Streptomyces coelicolor A3 (2)];
FIG. 12 shows an amino acid sequence (SEQ ID NO: 11) Scoe3 NCBI protein accession code CAB88833.1 GI:7635996 putative secreted protein. [Streptomyces coelicolor A3(2)];
FIG. 13 shows an amino acid sequence (SEQ ID NO: 12) Scoe4 NCBI protein accession code CAB89450.1 GI:7672261 putative secreted protein. [Streptomyces coelicolor A3(2)];
FIG. 14 shows an amino acid sequence (SEQ ID NO: 13) Scoe5 NCBI protein accession code CAB62724.1 GI:6562793 putative lipoprotein [Streptomyces coelicolor A3 (2)];
FIG. 15 shows an amino acid sequence (SEQ ID NO: 14) Srim1 NCBI protein accession code AAK84028.1 GI:15082088 GDSL-lipase (‘GDSL’ disclosed as SEQ ID NO: 122) [Streptomyces rimosus]; 
FIG. 16 shows an amino acid sequence (SEQ ID NO: 15) of a lipid acyltransferase from Aeromonas salmonicida subsp. Salmonicida (ATCC#14174);
FIG. 17 shows SEQ ID NO: 19. Scoe 1 NCBI protein accession code CAB39707.1 GI:4539178 conserved hypothetical protein [Streptomyces coelicolor A3(2)];
FIG. 18 shows an amino acid sequence (SEQ ID NO: 25) of the fusion construct used for mutagenesis of the Aeromonas hydrophila lipid acyltransferase gene. The underlined amino acids is a xylanase signal peptide;
FIG. 19 shows a polypeptide sequence of a lipid acyltransferase enzyme from Streptomyces (SEQ ID NO: 26);
FIG. 20 shows a polypeptide sequence of a lipid acyltransferase enzyme from Thermobifida (SEQ ID NO: 27);
FIG. 21 shows a polypeptide sequence of a lipid acyltransferase enzyme from Thermobifida (SEQ ID NO: 28);
FIG. 22 shows a polypeptide of a lipid acyltransferase enzyme from Corynebacterium efficiens GDSX (SEQ ID NO: 120) 300 amino acid (SEQ ID NO: 29);
FIG. 23 shows a polypeptide of a lipid acyltransferase enzyme from Novosphingobium aromaticivorans GDSX (SEQ ID NO: 120) 284 amino acid (SEQ ID NO: 30);
FIG. 24 shows a polypeptide of a lipid acyltransferase enzyme from Streptomyces coelicolor GDSX (SEQ ID NO: 120) 269 aa (SEQ ID NO: 31);
FIG. 25 shows a polypeptide of a lipid acyltransferase enzyme from Streptomyces avermitilis\GDSX (SEQ ID NO: 120) 269 amino acid (SEQ ID NO: 32);
FIG. 26 shows a polypeptide of a lipid acyltransferase enzyme from Streptomyces (SEQ ID NO: 33);
FIG. 27 shows an amino acid sequence (SEQ ID NO: 34) obtained from the organism Aeromonas hydrophila (P10480; GI:121051) (notably, this is the mature sequence);
FIG. 28 shows the amino acid sequence (SEQ ID NO: 35) of a mutant Aeromonas salmonicida mature lipid acyltransferase (GCAT) (notably, this is the mature sequence);
FIG. 29 shows a nucleotide sequence (SEQ ID NO: 36) from Streptomyces thermosacchari; 
FIG. 30 shows an amino acid sequence (SEQ ID NO: 37) from Streptomyces thermosacchari; 
FIG. 31 shows an amino acid sequence (SEQ ID NO: 38) from Thermobifida fusca/GDSX (SEQ ID NO: 120) 548 amino acid;
FIG. 32 shows a nucleotide sequence (SEQ ID NO: 39) from Thermobifida fusca; 
FIG. 33 shows an amino acid sequence (SEQ ID NO: 40) from Thermobifida fusca/GDSX (SEQ ID NO: 120);
FIG. 34 shows an amino acid sequence (SEQ ID NO: 41) from Corynebacterium efficiens/GDSX (SEQ ID NO: 120) 300 amino acid;
FIG. 35 shows a nucleotide sequence (SEQ ID NO: 42) from Corynebacterium efficiens; 
FIG. 36 shows an amino acid sequence (SEQ ID NO: 43) from S. coelicolor/GDSX (SEQ ID NO: 120) 268 amino acid;
FIG. 37 shows a nucleotide sequence (SEQ ID No: 44) from S. coelicolor; 
FIG. 38 shows an amino acid sequence (SEQ ID NO: 45) from S. avermitilis; 
FIG. 39 shows a nucleotide sequence (SEQ ID NO: 46) from S. avermitilis; 
FIG. 40 shows an amino acid sequence (SEQ ID NO: 47) from Thermobifida fusca/GDSX (SEQ ID NO: 120);
FIG. 41 shows a nucleotide sequence (SEQ ID NO: 48) from Thermobifida fusca/GDSX (SEQ ID NO: 120);
FIG. 42 shows an alignment of the L131 (SEQ ID NO: 26) and homologues from S. avermitilis (SEQ ID NO: 32) and T. fusca (SEQ ID NO: 40) illustrates that the conservation of the GDSX (SEQ ID NO: 120) motif (GDSY (SEQ ID NO: 125) in L131 and S. avermitilis and T. fusca), the GANDY (SEQ ID NO: 118) box, which is either GGNDA (SEQ ID NO: 123) or GGNDL (SEQ ID NO: 124), and the HPT block (considered to be the conserved catalytic histidine). These three conserved blocks are highlighted. Consensus sequence fragments disclosed as SEQ ID NOS 71-94, respectively, in order of appearance;
FIG. 43 shows SEQ ID No 17 which is the amino acid sequence of a lipid acyltransferase from Candida parapsilosis; 
FIG. 44 shows SEQ ID No 18 which is the amino acid sequence of a lipid acyltransferase from Candida parapsilosis; 
FIG. 45 shows a ribbon representation of the 1IVN.PDB crystal structure which has glycerol in the active site. The Figure was made using the Deep View Swiss-PDB viewer;
FIG. 46 shows 1IVN.PDB Crystal Structure—Side View using Deep View Swiss-PDB viewer, with glycerol in active site—residues within 10 Å of active site glycerol are coloured black;
FIG. 47 shows 1IVN.PDB Crystal Structure—Top View using Deep View Swiss-PDB viewer, with glycerol in active site—residues within 10 Å of active site glycerol are coloured black;
FIG. 48 shows alignment 1 (SEQ ID NOS 20, 96, and 97, respectively, in order of appearance);
FIG. 49 shows alignment 2 (SEQ ID NOS 95-97, respectively, in order of appearance);
FIGS. 50A-B and 51 show an alignment of 1IVN to P10480 (P10480 is the database sequence for A. hydrophila enzyme), this alignment was obtained from the PFAM database and used in the model building process (FIG. 50A-B discloses SEQ ID NOS 20, 96-97, and 95-97, and FIG. 51 discloses SEQ ID NOS 98-99, all respectively, in order of appearance); and
FIG. 52 shows an alignment where P10480 is the database sequence for Aeromonas hydrophila. This sequence is used for the model construction and the site selection. Note that the full protein (SEQ ID NO: 3) is depicted, the mature protein (equivalent to SEQ ID NO: 34) starts at residue 19. A. sal is Aeromonas salmonicida (SEQ ID NO: 35) GDSX (SEQ ID NO: 120) lipase, A. hyd is Aeromonas hydrophila (SEQ ID NO: 137) GDSX (SEQ ID NO: 120) lipase. The consensus sequence contains a * at the position of a difference between the listed sequences (consensus sequence fragments disclosed as SEQ ID NOS 102-114, respectively, in order of appearance).
FIG. 53 shows a gene construct used in Example 1;
FIG. 54 shows a codon optimised gene construct (no. 052907) used in Example 1; and
FIG. 55 shows the sequence of the XhoI insert containing the LAT-KLM3′ precursor gene, the −35 and −10 boxes are underlined (figure discloses the DNA sequence as SEQ ID NO: 115 and the protein sequence as SEQ ID NO: 116);
FIG. 56 shows BML780-KLM3′CAP50 (comprising SEQ ID NO: 16—upper colony) and BML780 (the empty host strain—lower colony) after 48 h growth at 37.degree. C. on 1% tributyrin agar;
FIG. 57 shows a nucleotide sequence from Aeromonas salmonicida (SEQ ID NO: 49) including the signal sequence (preLAT—positions 1 to 87);
FIG. 58 shows a nucleotide sequence (SEQ ID NO: 50) encoding a lipid acyl transferase according to the present invention obtained from the organism Aeromonas hydrophila; 
FIG. 59 shows a nucleotide sequence (SEQ ID NO: 51) encoding a lipid acyl transferase according to the present invention obtained from the organism Aeromonas salmonicida; 
FIG. 60 shows a nucleotide sequence (SEQ ID NO: 52) encoding a lipid acyl transferase according to the present invention obtained from the organism Streptomyces coelicolor A3(2) (Genbank accession number NC.sub.—003888.1:8327480.8328367);
FIG. 61 shows a nucleotide sequence (SEQ ID NO: 53) encoding a lipid acyl transferase according to the present invention obtained from the organism Streptomyces coelicolor A3(2) (Genbank accession number AL939131.1:265480.266367);
FIG. 62 shows a nucleotide sequence (SEQ ID NO: 54) encoding a lipid acyl transferase according to the present invention obtained from the organism Saccharomyces cerevisiae (Genbank accession number Z75034);
FIG. 63 shows a nucleotide sequence (SEQ ID NO: 55) encoding a lipid acyl transferase according to the present invention obtained from the organism Ralstonia; 
FIG. 64 shows a nucleotide sequence shown as SEQ ID NO: 56 encoding NCBI protein accession code CAB39707.1 GI:4539178 conserved hypothetical protein [Streptomyces coelicolor A3 (2)];
FIG. 65 shows a nucleotide sequence shown as SEQ ID NO: 57 encoding Scoe2 NCBI protein accession code CAC01477.1 GI:9716139 conserved hypothetical protein [Streptomyces coelicolor A3(2)];
FIG. 66 shows a nucleotide sequence shown as SEQ ID NO: 58 encoding Scoe3 NCBI protein accession code CAB88833.1 GI:7635996 putative secreted protein. [Streptomyces coelicolor A3 (2)];
FIG. 67 shows a nucleotide sequence shown as SEQ ID NO: 59 encoding Scoe4 NCBI protein accession code CAB89450.1 GI:7672261 putative secreted protein. [Streptomyces coelicolor A3(2)];
FIG. 68 shows a nucleotide sequence shown as SEQ ID NO: 60, encoding Scoe5 NCBI protein accession code CAB62724.1 GI:6562793 putative lipoprotein [Streptomyces coelicolor A3 (2)];
FIG. 69 shows a nucleotide sequence shown as SEQ ID NO: 61 encoding Srim1 NCBI protein accession code AAK84028.1 GI:15082088 GDSL-lipase (‘GDSL’ disclosed as SEQ ID NO: 122) [Streptomyces rimosus]; 
FIG. 70 shows a nucleotide sequence (SEQ ID NO: 62) encoding a lipid acyltransferase from Aeromonas hydrophila (ATCC #7965);
FIG. 71 shows a nucleotide sequence (SEQ ID NO: 63) encoding a lipid acyltransferase from Aeromonas salmonicida subsp. Salmonicida (ATCC#14174);
FIG. 72 shows a nucleotide sequence (SEQ ID NO: 24) encoding an enzyme from Aeromonas hydrophila including a xylanase signal peptide;
FIG. 73 shows the amino acid sequence of a mutant Aeromonas salmonicida mature lipid acyltransferase (GCAT) with a mutation of Asn80Asp (notably, amino acid 80 is in the mature sequence)—shown herein as SEQ ID No. 16—and after undergoing post-translational modification as SEQ ID NO: 68—amino acid residues 235 and 236 of SEQ ID No. 68 are not covalently linked following post-translational modification. The two peptides formed are held together by one or more S-S bridges. Amino acid 236 in SEQ ID NO: 68 corresponds with the amino acid residue number 274 in SEQ ID No. 16 shown herein;
FIG. 74 shows a turbiscan measurement from the top 5 mm;
FIG. 75 shows a turbiscan measurement from the bottom 5 mm;
FIG. 76 shows the surface tension of Pasterurized milk 12983-1-11 (control), 12983-1-12 (enzyme treated) and UHT milk 12983-1-13 (control), 12983-1-14 (enzyme treated);
FIG. 77 shows measurements of Milk free cholesterol and cholesterol-ester by Gas Chromatography. 11 and 12 were pasteurised milk and 13 and 14 were UHT milk. Sample −12 and −14 were enzymatically treated with KLM3 at 5° C. for 20 hours. A commercially available UHT milk from Arla was included in the analysis in comparison;
FIG. 78 shows HPTLC of extracted pasteurised (90° C.) and UHT (142° C.) milk lipids dissolved in CHCl3:MeOH (2:1). Standard (Std) 16 contains SpectraLipid Soy Lecithin Mix Standard (No. SLM43) dissolved in CHCl3:MeOH (2:1);
FIG. 79 shows the results of Lumifugation of Chocolate milk with KLM3 ((DK 14636-2-3);
FIG. 80 shows the results of Lumifugation of Chocolate milk without KLM 3 (DK14636-2-4):
FIG. 81 shows Clarification (% Integral Transmission);
FIG. 82 shows the results of Front tracking, i.e. monitoring the movement of the front of clearance at 15% transmission; and
FIG. 83 shows the results of Front tracking, i.e. monitoring the movement of the front of clearance at 50% transmission.



The invention will now be further described by way of the following non-limiting examples.
EXAMPLE 1
Expression of KLM3′ in Bacillus licheniformis 
A nucleotide sequence (SEQ ID NO: 49) encoding a lipid acyltransferase (SEQ. ID No. 16, hereinafter KLM3′) was expressed in Bacillus licheniformis as a fusion protein with the signal peptide of B. licheniformis [alpha]-amylase (LAT) (see FIGS. 53 and 54). For optimal expression in Bacillus, a codon optimized gene construct (no. 052907) was ordered at Geneart (Geneart AG, Regensburg, Germany).
Construct no. 052907 contains an incomplete LAT promoter (only the −10 sequence) in front of the LAT-KLM3′ precursor gene and the LAT transcription (Tlat) downstream of the LAT-KLM3′ precursor gene (see FIGS. 53 and 55). To create a XhoI fragment that contains the LAT-KLM3′ precursor gene flanked by the complete LAT promoter at the 5′ end and the LAT terminator at the 3′ end, a PCR (polymerase chain reaction) amplification was performed with the primers Plat5XhoI_FW and EBS2XhoI_RV and gene construct 052907 as template.







Plat5XhoI_FW:


(SEQ ID NO: 69)


ccccgctcgaggcttttcttttggaagaaaatatagggaaaatggtactt


 


gttaaaaattcggaatatttatacaatatcatatgtttcacattgaaa


 


gggg


 


EBS2XhoI_RV:


(SEQ ID NO: 70)


tggaatctcgaggttttatcctttaccttgtctcc






PCR was performed on a thermocycler with Phusion High Fidelity DNA polymerase (Finnzymes OY, Espoo, Finland) according to the instructions of the manufacturer (annealing temperature of 55[deg.] C.).
The resulting PCR fragment was digested with restriction enzyme XhoI and ligated with T4 DNA ligase into XhoI digested pICatH according to the instructions of the supplier (Invitrogen, Carlsbad, Calif. USA).
The ligation mixture was transformed into B. subtilis strain SC6.1 as described in U.S. Patent Application US20020182734 (International Publication WO 02/14490). The sequence of the XhoI insert containing the LAT-KLM3′ precursor gene was confirmed by DNA sequencing (BaseClear, Leiden, The Netherlands) and one of the correct plasmid clones was designated pICatH-KLM3′(ori1) (FIG. 53). plCatH-KLM3′(ori1) was transformed into B. licheniformis strain BML780 (a derivative of BRA7 and BML612, see WO2005111203) at the permissive temperature (37[deg.] C.).
One neomycin resistant (neoR) and chloramphenicol resistant (CmR) transformant was selected and designated BML780(plCatH-KLM3′(ori1)). The plasmid in BML780(plCatH-KLM3′(ori1)) was integrated into the catH region on the B. licheniformis genome by growing the strain at a non-permissive temperature (50[deg.] C.) in medium with 5 [mu]g/ml chloramphenicol. One CmR resistant clone was selected and designated BML780-plCatH-KLM3′(ori1). BML780-plCatH-KLM3′ (ori1) was grown again at the permissive temperature for several generations without antibiotics to loop-out vector sequences and then one neomycin sensitive (neoS), CmR clone was selected. In this clone, vector sequences of plCatH on the chromosome are excised (including the neomycin resistance gene) and only the catH-LATKLM3′ cassette is left. Next, the catH-LATKLM3′ cassette on the chromosome was amplified by growing the strain in/on media with increasing concentrations of chloramphenicol. After various rounds of amplification, one clone (resistant against 50 [mu]g/ml chloramphenicol) was selected and designated BML780-KLM3′CAP50. To verify KLM3′ expression, BML780-KLM3′CAP50 and BML780 (the empty host strain) were grown for 48 h at 37 [deg.] C on a Heart Infusion (Bacto) agar plate with 1% tributyrin. A clearing zone, indicative for lipid acyltransferase activity, was clearly visible around the colony of BML780-KLM3′CAP50 but not around the host strain BML780 (see FIG. 56). This result shows that a substantial amount of KLM3′ is expressed in B. licheniformis strain BML780-KLM3′CAP50 and that these KLM3′ molecules are functional.
COMPARATIVE EXAMPLE 1
Vector Construct
The plasmid construct is pCS32new N80D, which is a pCCmini derivative carrying the sequence encoding the mature form of the native Aeromonas salmonicida Glycerophospholipid-cholesterol acyltransferase with a Asn to Asp substitution at position 80 (KLM3′), under control of the p32 promoter and with a CGTase signal sequence.
The host strain used for the expression, is in the bacillus subtilis OS21ΔAprE strain
The expression level is measured as transferase activity, expressed as % cholesterol esterified, calculated from the difference in free cholesterol in the reference sample and free cholesterol in the enzyme sample in reactions with PC (TPC) as donor and cholesterol as acceptor molecule.
Culture Conditions
5 ml of LB broth (Casein enzymatic digest, 10 g/l; low-sodium Yeast extract, 5 g/l; Sodium Chloride, 5 g/l; Inert tableting aids, 2 g/l) supplemented with 50 mg/l kanamycin, was inoculated with a single colony and incubated at 30° C. for 6 hours at 205 rpm. 0.7 ml of this culture was used to inoculate 50 ml of SAS media (K2HPO4, 10 g/l; MOPS (3-morpholinopropane sulfonic acid), 40 g/l; Sodium Chloride, 5 g/l; Antifoam (Sin 260), 5 drops/l; Soy flour degreased, 20 g/l; Biospringer 106 (100% dw YE), 20 g/l) supplemented with 50 mg/l kanamycin and a solution of high maltose starch hydrolysates (60 g/l). Incubation was continued for 40 hours at 30° C. and 180 rpm before the culture supernatant was separated by centrifugation at 19000 rpm for 30 min. The supernatant was transferred into a clean tube and directly used for transferase activity measurement.
Preparation of Substrates and Enzymatic Reaction
PC (Avanti Polar Lipids #441601) and cholesterol (Sigma C8503) was scaled in the ratio 9:1, dissolved in chloroform, and evaporated to dryness.
The substrate was prepared by dispersion of 3% PC:Cholesterol 9:1 in 50 mM Hepes buffer pH 7.
0.250 ml substrate solution was transferred into a 3 ml glass tube with screw lid. 0.025 ml culture supernatant was added and the mixture was incubated at 40° C. for 2 hours. A reference sample with water instead of enzyme was also prepared. Heating the reaction mixture in a boiling water bath for 10 minutes stopped the enzyme reaction. 2 ml of 99% ethanol was added to the reaction mixture before submitted to cholesterol assay analysis.
Cholesterol Assay
100 μl substrate containing 1.4 U/ml Cholesterol oxidase (SERVA Electrophoresis GmbH cat. No 17109), 0.4 mg/ml ABTS (Sigma A-1888), 6 U/ml Peroxidase (Sigma 6782) in 0.1 M Tris-HCl, pH 6.6 and 0.5% Triton X-100 (Sigma X-100) was incubated at 37° C. for 5 minutes before 5 μl enzyme reaction sample was added and mixed. The reaction mixture was incubated for further 5 minutes and OD405 was measured. The content of cholesterol was calculated from the analyses of standard solutions of cholesterol containing 0.4 mg/ml, 0.3 mg/ml, 0.20 mg/ml, 0.1 mg/ml, 0.05 mg/ml, and 0 mg/ml cholesterol in 99% EtOH.
Results
The table shows the average of 8 separate expression cultures













Strain
TPCa








OS21ΔAprE[pCS3
7.42 ± 10.1b



2new]





aTPC is the transferase activity, expressed as % cholesterol esterified, calculated from the difference in free cholesterol in the reference sample and free cholesterol in the enzyme sample in reactions with PC as donor molecule and cholesterol as acceptor molecule.


bAverage of 8 separate expression cultures






EXAMPLE 2
Emulsion Stability, Removal of Cholesterol in UHT Milk
The use of the lipid acyltransferase shown here as SEQ ID NO: 68 (hereinafter referred to as “KLM3”) for interesterification and/or transesterification between phospholipids and cholesterol in UHT milk has an effect on improving the emulsion stability, comparing results in ordinary UHT milk and Flavoured UHT milk, produced on basis of fresh milk as well as recombined milk.
For the avoidance of doubt recombined milk is a general term for milk, which is produced from original milk based solid components mixed with water and processed in such a way to produce milk with similar characteristics as the original milk.
Test of KLM3 in UHT Milk and Cream


















COMPOSITION IN










PERCENTAGES
1
2
3
4
5
6
7
8























Milk 3.5% fat
99.90
99.90
99.90
94.16






Skim milk powder




9.00
9.00
9.00
9.00


Butter oil (AMF)




3.50
3.50
3.50
3.50


Sucrose



5.50



5.50


Strawberry Flavouring



0.12



0.12


T10063










Carmine Extract (red)



0.02



0.02


RECODAN TM RS 100
0.10
0.10
0.10
0.20
0.15
0.15
0.15
0.20


K460 (KLM3)

75 U/L
40 U/L
75 U/L

75 U/L
40 U/L
75 U/L


Units/liter










Water (Tap)




87.35
87.35
87.35
81.66


Total percentage
100.00
100.00
100.00
100.00
100.00
100.00
100.00
100.00









The samples (recombined milk) were processed in Dairy Pilot Plant as follows:

Pilot (Batch Preparation)

1.—Heat water/milk to 40° C. in mixer tank and add enzymes

2.—Add skimmed milk powder, sugar, other dry ingredients to the water and keep for 30 minutes

3.—Melt butteroil at 70° C.

4.—Add stabiliser/emulsifier to the melted butteroil

5.—Add butteroil, stabiliser/emulsifier to the milk

6.—Add flavorings.

7.—Premix on silverson—medium speed for 1 minute

8.—Dearate for approximately 30 minutes in the bucket

The fresh milk followed step 1, 2, 6, 7 and 8.

UHT—(PHE)

9.—Preheat to 90° C. (holding cell at 30 seconds)

10.—Indirect heating 142° C. for 3 seconds

11.—Downstream homogenisation 200 bar, 75° C.

12.—Cool to 15° C.

13.—Aseptic Filling

The ingredients used for the trials were commercially purchased whole milk and/or standard raw materials used for majority of trials in the Dairy Pilot Plant.
The enzyme solution used was a sample of KLM3 (K460—shown as SEQ ID NO: 68 herein). The K460 contains 1400 TIPU units/ml.
TIPU Assay
Substrate
0.6% L-α Phosphatidylcholine 95% Plant (Avanti #441601), 0.4% Triton-X 100 (Sigma X-100) and 5 mM CaCl2 was dissolved in 0.05M HEPES buffer pH 7.
Assay Procedure:
400 μl substrate was added to an 1.5 ml Eppendorf tube and placed in an Eppendorf Thermomixer at 37° C. for 5 minutes. At time T=0 min, 50 μl enzyme solution was added. Also a blank with water instead of enzyme was analyzed. The sample was mixed at 10*100 rpm in an Eppendorf Thermomixer at 37° C. for 10 minutes. At time T=10 min the Eppendorf tube was placed in another thermomixer at 99° C. for 10 minutes to stop the reaction.
Free fatty acid in the samples was analyzed by using the NEFA C kit from WAKO GmbH.
Enzyme activity TIPU pH 7 was calculated as micromole fatty acid produced per minute under assay conditions.
The dosage level of enzymes was 75 and 40 units per liter. Reaction time and temperature was in this experiment constant at 40° C. for 30 min.
In order to evaluate results from the trial, all samples were analysed as follows:

    
    
        Remaining content of cholesterol and phospholipids
        Particle size distribution in water and with 1% SDS added
        Viscosity and sediment (DLA standard methods in Dairy Pilot Plant) Viscosity is measured in centipoises on a Brookfield Viscosimeter with spindle 2 at 60 rpm and 4° C. Sedimentation is measured by the Sedimentation test in % when subjecting a product sample to centrifugal force of 2800 g for 20 minutes and 20° C. (Ultracentrifuge) and then calculate pellet at % of total sample.
    
    


Particle size was measured by Malvern Mastersizer S long bed, configuration Alpha, Linse 300R. The instrument was calibrated with a polymer standard to a specification of 0.993 μm±0.021 μm. The sample is diluted in water (2 g sample to 10 ml water with 1% SDS). SDS was added to avoid particles aggregation, as aggregation will give a false result.
Results
Analysis Results:



















Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8







Cholesterol
Normal
Completely
Completely
Completely
Normal
Partly
Partly
Partly



level
esterified
esterified
esterified
level
esterified
esterified
esterified


Phospholipids
Normal
Not
Not
Not
Normal
Not
Not
Not



level
present
present
present
level
present
present
present









Particle Size Analysis:




















Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8







Mean particle
0.57
0.58
0.58
0.53
0.55
0.54
0.53
0.49


diameter μm









All samples have a mean particle size under 1 μm.
Samples are weighed and then subjected to ultracentrifugation at 2800 G for 20 minutes and at 20° C. After centrifugation the supernatant is removed and the dry pellet is weighed and sediment is calculated as percentage of original sample size. As noted above viscosity is measured in centipoises and sedimentation in %.



















Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8























Viscosity
5
6
6
22
15
15
17
28


Sediment
2.1
0.8
1.2
0.7
1.4
0.6
0.5
0.5









Results show that use of KLM3 can improve the emulsion stability in UHT milk, and remove the cholesterol.
EXAMPLE 3
Effect of KLM-3 Enzyme in Pasteurized or UHT Treated Milk
Materials and Methods
Glycerophospholipid cholesterol acyltransferase KLM3 (K460)
Recodan RS 100: Stabilizer system
Cream: Commercial source
Skim milk: Commercial source.
EXPERIMENTAL
In order to further establish whether the use of KLM3 in milk has an effect on improving the emulsion stability the following trial run was made, comparing results in ordinary UHT milk and pasteurised milk, produced on basis of recombined fresh milk. In this experiment the enzyme reaction was conducted at 5° C.
Test of KLM3 in pasteurised (sample 11 and 12) and UHT milk (sample 13 and 14)














Composition in %
11
12
13
14



















RECODAN RS 100
0.15
0.15
0.13
0.13


Cream 38% fat
8.61
8.61
8.66
8.66


Skimmed milk
91.24
91.24
91.21
91.21


KLM3, 100 U/ml
−
+
−
+


Temperature ° C.
90
90
142
142


Holding time in seconds
30
30
3
3









The said samples were processed in the Dairy Pilot Plant as follows:
Sample 11, 12, 13 and 14:
UHT milk—Pilot (PHE)
1.—Mix skim milk and cream
2.—Add KLM 3 enzyme and stir well.
3.—Leave in cold store overnight (20 hr.)
4.—Heat milk to 60° C. and add Recodan
Sample 13 and 14:
5.—Preheat to 90° C. (holding cell at 30 seconds)
6.—Indirect heating 142° C. for 3 seconds
7.—Downstream homogenisation 200 bar, 75° C.
8.—Cool to 15° C.
9.—Aseptic Filling
Sample 11 and 12:
10.—Homogenise up stream at 70° C. and 200 bar
11.—Pasteurise at 90° C. for 30 sec
12.—Cool to 5° C. and fill
The ingredients used for the trials were commercially purchased whole milk and/or standard raw materials used for majority of trials in the Dairy Pilot Plant.
The dosage level of enzymes was the same as in the other examples herein showing with KLM3 enzymation of milk at 5° C.
In order to evaluate results from the trial, all samples were analysed as follows:

    
    
        Turbiscan over 5 days
        Stress test of the UHT samples (long term stability)
        Surface Tension.
        Cholesterol and phosphatidylethanolamine
        Sensoric analysis by Triangle Test

Turbiscan:

    
    


Turbiscan MA 2000 was used to measure the stability of emulsions by measuring the backscatter of a laser beam from the product.
The milk samples were filled aseptically into a sterile test tube, the test tubes were kept at ambient temperature. The samples were measured at regular intervals over a period of 5-7 days.
Samples were measured from top 5 mm and bottom 5 mm of the test tube, where increase in back scattering from the top layer indicates creaming and increase in the bottom indicates sedimentation of particles in the sample.
STRESS Test of Neutral UHT Milk Products


    
    
        1. After aseptic filling (typically at ambient temp.) Sample 13 and 14 were placed overnight in cold store at 5° C.
        2. Samples were then transferred to an incubator at 35° C. for 24 hours
        3. Samples were transferred to Cold Store at 5° C. for 24 hours
        4. Samples were transferred to ambient temperature of 20-25° C. for 24 hours
        5. Samples were transferred to Cold Store at 5° C. for 24 hours
    
    


After said temperature treatment, the samples were left at ambient temperature for 2-3 days and is then evaluated visually for Creaming, flocculation, Sedimentation and possible phase separations.
The correlation of this test with actual long-life stability of products has through 2 years observations proved to be having a very high correlation.
Surface Tension:
The surface tension of the milk samples was measured with a Wilhelmy plate using a Tensiometer K10 from Krüss
Gas Chromatography:
Gas Chromatography was used to measure the content of cholesterol and cholesterol-ester in the milk samples.
The following CG setup was used:
Perkin Elmer Autosystem 9000 Capillary Gas Chromatograph equipped with WCOT fused silica column 12.5 m×0.25 mm ID×0.1μ film thickness 5% phenyl-methyl-silicone (CP Sil 8 CB from Chrompack).
Carrier gas: Helium.
Injector. PSSI cold split injection (initial temp 50° C. heated to 385° C.), volume 1.0 μl
Detector FID: 395° C.














Oven program:













1
2
3















Oven temperature, ° C.
90
280
350



Isohtermal, time, min.
1
0
10



Temperature rate, ° C./min.
15
4









Preparation of Milk Samples for Gc Analysis:

The milk lipids are extracted according to Mojonnier AOAC 989.05 using ethanol, NH3, MTBE (methyl-tert-butyl ether) and p-ether. The lipid fraction is redissolved in heptane/pyridine (2:1) containing heptadecan as internal standard and cholesterol is measured by GC.
Preparing samples for cholesterol-ester measurements Squalane is added as an additional internal standard. The lipid fraction is redissolved in hexane and cholesterol-esters are concentrated using a NH2 Bond Elut column and hexane eluation. Samples are redissolved in heptane/pyridine (2:1) and cholesterol-esters are measured by CG.
HPTLC:
HPTLC is used to measure the content of phosphatidylethanolamine (PE) in pasteurised milk samples and UHT milk samples.
Applicator: CAMAG applicator AST4.
HPTLC plate: 20×10 cm (Merck no. 1.05641)
The plate is activated before use by drying in an oven at 160° C. for 20-30 minutes.
Application: 6.0 μl of extracted lipids dissolved in CHCl3:Methanol (2:1) are applied to the HPTLC plate using AST4 applicator.
0.1, 0.3, 0.5, 0.8, 1.5 μl of a standard solution containing standard components with known concentration are also applied to the HPTLC plate
Running-buffer 6: Methylacetate:CHCl3:1-propanol:MeOH:0.25% KCl (25:25:25:10:9)
Elution length: 7 cm
Developing fluid: 6% Cupriacetate in 16% H3PO4 
After elution the plate is dried in an oven at 160° C. for 10 minutes, cooled and immersed in the developing fluid (10 sec) and then dried additional for 6 minutes at 160° C. The plate is evaluated visually and scanned (Camag TLC scanner).
Triangle Test.
ISO 4120:2004 Sensory analysis—Methodology—Triangle test
ISO 4120:2004 describes a procedure for determining whether a perceptible sensory difference or similarity exists between samples of two products. The triangle test is a three-alternative test in which one sample is different from the other two.
The test is counterbalanced for the identity of the odd sample (both ABB and BAA used) and its position in tasting (ABB, BAB, BBA, AAB, ABA, BAA). Chance performance is one third, and performance in a group above that level provides evidence for a perceivable difference. The method is a forced-choice procedure. The method applies whether a difference can exist in a single sensory attribute or in several attributes.
Results
TURBISCAN Measurements
Results from Turbiscan measurements of pasteurized or UHT milk are shown in the Table below and also in FIG. 74 and FIG. 75.







TABLE





Turboscan measurement of Pasterurized milk 12983-1-11 (control),


12983-1-12 (enzyme treated) and UHT milk 12983-1-13 (control),


12983-1-14 (enzyme treated)







Average top 5 mm












Relative





Time (min)
12983-1-11
12983-1-12
12983-1-13
12983-1-14





0
0.00
0.00
0.00
0.00


1
−0.04
−0.51
−0.11
0.08


1225
1.31
2.55
−0.53
−0.68


2683
2.11
2.81
−1.09
−0.02


6951
4.30
2.89
−0.58
0.04










Average bottom 5 mm











Time (min)
12983-1-11
12983-1-12
12983-1-13
12983-1-14





0
0.00
0.00
0.00
0.00


1
−0.25
0.09
−0.06
−0.12


1225
−1.80
−1.91
−0.10
0.11


2683
−3.03
−2.21
−0.50
0.12


6951
−4.22
−2.71
−0.65
0.17









The TURBISCAN measurements show decreased creaming and decreased sedimentation in the pasteurised samples, the storage time was too short to determine the effect in UHT milk. Storage stability of the UHT milk was therefore determined by the Stress test.
Stress Test of Enzymatically Treated Milk in Trial DK 12938














Evaluation after stress test,



Sample
placed 3 weeks at 30° C.








13 (no enzymatic treatment)
Slight creaming 0-1 mm



14 (enzymatic treatment)
Sample stable









After 3 weeks at 30° C. a significant difference was observed between the control and the enzyme treated sample.
Surface Tension
The surface tension of the milk samples were measured at 20° C. using a Kruss Tensiometer.
The results are illustrated in FIG. 76.
The results form surface measurement indicates a significant effect of enzymatic treatment of milk with KLM3.
Gas Chromatography of Free Cholesterol and Cholesterol-Ester.
Results of Gas Chromatography measurements of milk cholesterol and cholesterol-ester are shown in FIG. 77.
In general GC results from enzymatic treatment of both pasteurised and UHT milk with KLM3 acyltransferase confirms the ability of this enzyme to convert cholesterol into cholesterol-ester. KLM3 treatment of milk samples reduces free cholesterol by 85-90% in UHT as well as pasteurized milk. In addition KLM3 treatment increased cholesterol-ester level in pasteurized and UHT milk by a factor  ̃6 and  ̃10, respectively. A clear effect is thus observed from KLM3 treatment of pasteurized and UHT milk with respect to reduction of free cholesterol.
Pasteurised and UHT milk controls both resembled the commercial UHT milk from ARLA with respect to free cholesterol and cholesterol-ester levels.
HPTLC of Milk Phosphatidylethanolamine:
Results of milk lipids extracted from pasteurised and UHT milk and measured by HPTLC are shown in FIG. 78.
HPTLC Measurements.
Enzymatic treatment of both pasteurised and UHT milk with KLM3 show a marked reduction in milk phosphatidylethanolamine (PE) content as presented in the table below.







TABLE







Milk phosphatidylethanolamine quantified from


HPTLC plate scan. SpectraLipid, Soy Lecithin Mix


Standard (No. SLM43) was used in the quantification.












Pasteurised milk

UHT milk













12983-1-11
12983-1-12
12983-1-13
12983-1-14






18.7 ppm
1.5 ppm
23.3 ppm
3.4 ppm









The reduction in milk PE content as a response of KLM3 enzymatic treatment and thus the formation of partially hydrolyzed PE (Lyso-PE) correspond to a better emulsion stability and less tendency to creaming over time. In addition, the reduced milk PE corresponds to the formation of cholesterol-esters and a reduction of free cholesterol as given in FIG. 77, and further a better emulsion stability.
Triangle Test
Organoleptic differences between control and enzyme treated pasteurised or UHT milk were evaluated by a triangle test. The results from the tests is outlined in the table below:







TABLE







Triangle tests of UHT milk and Pasteurised (PAST) milk.














Without
Answers
Answers



Test no
Results of tests (Alpha risks)
Answer
Taken
Right
Signif.















1
UHT without enzyme/UHT with enzyme
0
8
1
0.961


3
UHT without enzyme/UHT with enzyme
0
8
4
0.259


5
UHT without enzyme/UHT with enzyme
0
8
5
0.088


Average
UHT without enzyme/UHT with enzyme
0
24
10
0.2538


1-3-5







2
PAST without enzyme/PAST with enzyme
0
8
3
0.532


4
PAST without enzyme/PAST with enzyme
0
8
2
0.805


6
PAST without enzyme/PAST with enzyme
0
8
5
0.088


Average
PAST without enzyme/PAST with enzyme
0
24
10
0.2538


2-4-6









The triangle test shows that treatment with the enzyme (KLM3) does not adversely affect the taste of UHT milk or pasteurized milk compared with milk without enzyme addition.
EXAMPLE 4
Preparation of Chocolate Milk
Materials and Methods
Glycerophospholipid cholesterol acyltransferase KLM3 (K932) (SEQ ID NO: 68): 1128 LATU/g
Soy Lecithin Mix Standard (ST16) from Spectra Lipid, Germany.
Recipe













Sample no 1
Sample no 2


Ingredient Name
DK14636-2-3
DK14636-2-4

















Skimmed milk
89.496
89.496


Cream 38% fat
2.804
2.804


Sucrose
6.000
6.000


Cocoa powder D-11A (light alk.)
1.500
1.500


GRINDSTED ® Carrageenan CL 220
0.020
0.020


CREMODAN ® SUPER
0.180
0.180


Mono-diglyceride




KLM3
+0.01




LATU/ml



Total %
100
100









Process

Add KLM3 (100 U/ml) to the pasteurised skimmed milk for sample DK14636-2-3, at a dosage of 0.100 ml KLM3 per liter milk

Agitate for two minutes

Place in cold store at 5° C. for 24 hours

Also place the milk for sample no DK14636-2-4 in the cold store at 5° C. for 24 hours.

After 24 hours storage at 5° C., heat the milk to 70° C. and add all other ingredients

Heat to 90° C. for 30 seconds

UHT treatment (plate heat exchanger) 139-142° C./2-4 sec.

Homogenise at 150 bar/50 bar and 75° C.

Cool to 10-15° C.

Transfer to cold store

Store at below 5° C.

Preparation of Cocoa Milk Samples for GC and TLC Analysis:

2 gram Cocoa milk was scaled in a 12 ml test tube with screw lid. 10 Hexan:Isopropanol 3:2 was added.
The sample was mixed on a Whirley and extracted on a rotamix 30 rpm for 30 minutes.
The test tube was centrifugated at 1720 rcf for 10 minutes. The upper phase accounting 8.5 ml was isolated.
5 ml solvent phase was transferred to a 10 ml Dramglass an evaporated to dryness at 50° C. under a steam of nitrogen. The sample was re-dissolved in 0.400 ml Chloroform:Methanol 2:1 and used for TLC analysis.
Another 2 ml of the solvent phase was isolated, evaporated at 50° C. under a stream of Nitrogen and used for GLC analysis
Gas Chromatography:
Gas Chromatography is used to measure the content of cholesterol and cholesterol-ester in the lipid from Cocoa milk samples.
The following CG setup is used:
Perkin Elmer Autosystem 9000 Capillary Gas Chromatograph equipped with WCOT fused silica column 12.5 m×0.25 mm ID×0.1μ film thickness 5% phenyl-methyl-silicone (CP Sil 8 CB from Chrompack).
Carrier gas: Helium.
Injector. PSSI cold split injection (initial temp 50° C. heated to 385° C.), volume 1.0 μl
Detector FID: 395° C.














Oven program













1
2
3















Oven temperature, ° C.
90
280
350



Isohtermal, time, min.
1
0
10



Temperature rate, ° C./min.
15
4









HPTLC:

HPTLC is used to measure the content of phosphatidylethanolamine (PE) and Phosphatidylcholine (PC) in the isolated lipid from Cocoa milk samples.
Applicator: CAMAG applicator AST4.
HPTLC plate: 20×10 cm (Merck no. 1.05641)
The plate is activated before use by drying in an oven at 160° C. for 10 minutes.
Application: 6.0 μl of extracted lipids dissolved in CHCl3:Methanol (2:1) are applied to the HPTLC plate using AST4 applicator.
0.1, 0.3, 0.5, 0.8, 1.5 μl of a standard solution containing standard components of phospholipids with known concentration are also applied to the HPTLC plate
Running-buffer 6: Methylacetate:CHCl3:1-propanol:MeOH:0.25% KCl (25:25:25:10:9)
Elution length: 7 cm
Developing fluid: 6% Cupriacetate in 16% H3PO4 
After elution the plate is dried in an oven at 160° C. for 10 minutes, cooled and immersed in the developing fluid (10 sec) and then dried additional for 6 minutes at 160° C. The plate is evaluated visually and scanned (Camag TLC scanner). Phospholipid components are quantified based on calibration curves from the standard phospholipid composition.
Turbiscan:
Turbiscan MA 2000 is used to measure the stability of emulsions by measuring the backscatter of a laser beam (Lumifugation) from the product.
Results
The results from GLC and TLC analysis of lipid extracted form Cocoamilk treated with KLM3′ and a control sample without enzyme treatment is seen in Table 1.







TABLE 1







GLC and TLC analysis of lipid from Cocoa milk










Cocoa milk
Cocoa milk



Enzyme treated
Control



ppm
Ppm














GLC-analysis





Free fatty acids
300
292



Cholesterol
33
60



Cholesterol ester
48
6



TLC-analysis





Phosphatidylethanolamine
10.5
27.3



Phosphatidylcholine
2.8
24.9









The results in Table 1 indicate that almost half of the cholesterol in the Cocoa milk has been esterified by the enzyme treatment. And the amount of phospholipids in the enzyme treated sample was reduced. The results indicate that KLM3′ is more active on phosphatidylcholine than on phosphatidylethanolamine in the Cocoa milk.
Lumifugation of Chocolate Milk with and without KLM 3 (DK14636-2)
Experimental: Lumifugation has been carried out with 300 rpm (12×g), centrifugation glass no. 2 and the results are shown in FIG. 79 (DK 14636-2-3) and FIG. 80 (DK14636-2-4).
Clarification (% Integral Transmission):













Sample no.
% Change in Transmission/hour ×103








Sample 1 DK 14636-2-3
64



Sample 2 DK14636-2-4
72









The results are shown in FIG. 81.
As the change in the transmission is a measure of the rate in the clearance, sample 2 is the most unstable.
In order to investigate the rate of clearance front tracking has been performed.
Front tracking, i.e. monitoring the movement of the front of clearance, at 15% transmission (see FIG. 82)














Sample no
μm/sec at 12xg
mm/month at 1xg








Sample 1 DK 14636-2-3
0.0067
1.45



Sample 2 DK 14636-2-4
0.0242
5.23









Front tracking at 50% transmission (see FIG. 83) together with the front tracking at 15% (see FIG. 82) shows the difference in the clearance of the two samples, as sample 1 has approx. 1 mm clearance (50% T) supernatant, while sample 2 has a 2 mm less transparent supernatant. This is the result of a broader particle size distribution in sample 2.
Conclusion:
The enzyme treated sample is the most stable sample and further it has the most narrow particle size distribution
EXAMPLE 5
Comparison of KLM3′ (K932) with Different Phospholipases
Materials and Methods
Lipid acyltransferase—KLM3′ (K932)
A fungal lipolytic enzyme obtainable from Fusarium heterosporum CBS 782.83 (hereinafter referred to a “KLM1” from Danisco A/S) as taught in WO2005/087818.
Phospholipase A1 from Fusarium oxysporum (LIPOPAN FTM) from Novozymes
Pphospholipase A2 from Porcine pancreas (LIPOMOD 699 LTM) from Biocatalysts, UK
Standard pasteurised Whole Milk (3.5% fat) from ARLA in Denmark
Enzymated milk was investigated in comparison to reference milk in terms of stability against creaming visual evaluation of creaming, sedimentation and phase separation in samples stored over 60 days.
Furthermore the amount of free fatty acids in the milk was analyzed to evaluate level of rancidity in final product, and amount of cholesterol and/or phospholipids was analyzed to get an indication of enzymatic reaction level.
EXPERIMENTAL
Preparation of Milk







TABLE







Recipe


Ingredients in %













Ingredient Name
1
2
3
4
5
6
















Whole milk 3.5% fat
100.000
100.000
100.000
100.000
100.000
100.000


KLM1



10








LATU/ml




KLM3′

0.01



0.25




LATU/ml



LATU/ml


LIPOPAN F


5








LATU/ml





Lipomod 699 L




0.25








e-








PLU/ml



Total %
100
100
100
100
100
100









Process

1. Cold milk was mixed with enzyme portion and mixture was left in cold store overnight

2. Preheating to 90° C. for 30 sec

3. UHT treatment at 142° C. for 3 sec

4. Homogenise at 75° C. and 200 bar

5. Cool to 20° C. and fill aseptically in 6 bottles








TABLE







Real time shelf-life test














Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6





Cream Layer
4 mm
1 mm
3 mm
2 mm
3 mm
 2 mm


Sediment layer
0 mm
0 mm
12 mm
1 mm
2 mm
<1 mm


Organoleptic
Typical
As sample
Grainy
As sample 1
As sample 1
As sample 1


evaluation
UHT
1,
texture






flavour,
however,
with very






slightly
slightly
strong






cooked
less
rancidity







cooked









Samples prepared by UHT processing as described earlier were stored at ambient temperatures (18-25° C.) for a period of 60 days, where after the samples were evaluated for creaming layer as well as eventual phase separation or sedimentation in the bottom of the bottles.
Samples were furthermore tested by a trained panel of 6 persons, with a tasting session made as a randomised triangle test with sample 1 (plain UHT milk) used as the reference sample in all test sessions.
Both for real time observation of stability as well as organoleptic evaluation, it can be seen that sample 3 (enzymated with LIPOPAN FTM) gives significantly deviating results, with lower stability and strong lipolytic flavour in samples.
KLM3′ (samples 2 and 6) reduced the cream layer without forming a sediment layer and showed a marked improvement compared with the control 1.
The phospholipase treated samples 3, 4 and 5 may also reduced the cream layer compared with the control (although not to the same degree as KLM3′), but this was at the expense of forming a sediment layer.
With regard to organoleptic properties, sample 2 (KLM3′) had a slightly less cooked taste compared with the control 1. Hence sample 2 has an improved taste compared with the control 1. Lipopan FTM (sample 3) produced milk with bad organoleptic properties, probably due to the high level of free fatty acids produced.
HPTLC and GLC Analysis
Enzyme treated UHT milk according to the recipes shown in the table was extracted with organic solvents and the isolated lipids were analyzed for phospholipids by HPTLC and for cholesterol, cholesterol ester and free fatty acids (FFA) by Gaschromatography (GLC).







TABLE







HPTLC analysis of main phospholipids in milk


PC = phosphatidylcholine


PE = phosphatidylethanolamine.














PC
PE
Sum PC + PE
Degree of


Sample
Dosage
ppm
ppm
Ppm
hydrolysis %















Control

26.6
61.4
88.0
0


KLM3*
0.01 TIPU/ml
9.0
10.9
19.9
77


Lipopan F
5 TIPU/ml
3.9
7.8
11.8
87


KLM1
10 TIPU/ml
14.6
14.6
29.2
67


Lipomod
0.25 e-
5.1
2.0
7.2
92


699L
PLU/ml






KLM3′
TIPU/ml
5.0
2.0
7.0
92
















TABLE







GLC analysis of cholesterol, cholesterol ester and free fatty acids (FFA)















Cholesterol


Sample
Dosage
FFA total %
Cholesterol %
ester %





Control
0
0.022
0.015
0.0012


KLM3*
0.01 TIPU/g
0.029
0.009
0.0106


Lipopan F
5 TIPU/g
0.620
0.016
0.0014


KLM1
10 TIPU/g
0.159
0.016
0.0015


Lipomod
0.25 e-
0.042
0.014
0.0010


699L
PLU





KLM3′
TIPU/g
0.065
0.001
0.0215









The results form HPTLC analysis (see Table above) indicate that all enzymes tested were able to hydrolyse a main part of the phospholipids in the milk accounting from 77% to 92%, but only the lipid acyltransferease KLM3′ were able to make a transfer reaction of fatty acid to cholesterol during formation of cholesterol ester.
Although all enzymes produced a high degree of phospholipid hydrolysis the amount of free fatty acids produced were significantly different. Based of the amount of phospholipid hydrolysis and free fatty acid produced it is possible to calculate on a molar basis the amount of free fatty acid relative to the amount of phospholipids produced (see the table below). These results clearly demonstrate that the microbial phospholipases A1 produces much more free fatty acid that KLM3, because these phospholipases are not specific but also hydrolysis triglycerides (milk fat). Pancreas phospholipase (Lipomod 699 L) is known to be very specific for the phospholipids, but still produces more free fatty acids than the low dosage of KLM3′. At the high dosage of KLM3′ more fatty acid are produced than pancreas phospholipase, but this is explained by activity on lyso-phospholipids. Lipopan F produced the highest amount of free fatty acid because of the hydrolytic activity on triglycerides, which contributed to the negative evaluation in the organoleptic test.







TABLE







Formation of free fatty acid (FFA) relative to the amount


of hydrolysed phospholipids













FFA change
PL change
FFA/PL


Sample
Dosage
mmol/kg
mmol/kg
mol. ratio














Control
0
0
0
—


KLM3*
0.01 TIPU/g
0.279
0.093
3


Lipopan F
5 TIPU/g
21.7
0.103
210


KLM1
10 TIPU/g
4.98
0.080
62


Lipomod 699L
0.25 e-
0.742
0.110
7



PLU





KLM3′
TIPU/g
1.58
0.110
14









In conclusion: KLM3′ showed an enhanced stability (with a reduced cream layer without formation of a sediment layer) compared with both the control (without enzyme) and the comparative phospholipase enzymes. Without wishing to be bound by theory the reason for the enhanced stability may be due to a reduced particle size distribution of the fat globules in milk treated with KLM3′.
A further important effect is that KLM3′ produces much less free fatty acid compared with the same concentration of phospholipase. During extended storage at ambient temperatures free fatty acid can easily result in more oxidation of the milk and thus later cause organoleptic problems. Thus high free fatty acid content may cause significant problems in UHT milk which is typically stored at ambient temperatures for more than a month.
All publications mentioned in the above specification are herein incorporated by reference. Various modifications and variations of the described methods and system of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in biochemistry and biotechnology or related fields are intended to be within the scope of the following claims.
The invention is further described by the following numbered paragraphs:
1. A method of producing UHT milk, wherein said method comprises admixing a lipid acyltransferase and milk or a fraction thereof and treating the enzyme treated milk by ultra-heat treatment to produce UHT milk.
2. A method according to paragraph 1 wherein the lipid acyltransferase is added to the UHT milk and incubated therewith at a temperature of less than about 20° C., preferably less than about 10° C.
3. A method according to paragraph 1 or paragraph 2 wherein the lipid acyltransferase is added to the UHT milk and incubated therewith at a temperature of between about 1° C. and about 10° C., preferably between about 3° C. and about 7° C., more preferably about 5° C.

4. A method according to any one of paragraphs 1 to 3 wherein the lipid acyltransferase comprises a GDSx (SEQ ID NO: 120) motif and/or a GANDY (SEQ ID NO: 118) motif.

5. A method according to any one of the preceding paragraphs wherein the lipid acyltransferase enzyme is characterised as an enzyme which possesses acyltransferase activity and which comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S.

6. A method according to any one of the preceding paragraphs wherein the lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be obtainable, preferably obtained, from an organism from one or more of the following genera: Aeromonas, Streptomyces, Saccharomyces, Lactococcus, Mycobacterium, Streptococcus, Lactobacillus, Desulfitobacterium, Bacillus, Campylobacter, Vibrionaceae, Xylella, Sulfolobus, Aspergillus, Schizosaccharomyces, Listeria, Neisseria, Mesorhizobium, Ralstonia, Xanthomonas and Candida. 

7. A method according to paragraph 6 wherein the lipid acyltransferase is obtainable, preferably obtained, from an organism from the genus Aeromonas. 

8. A method according to any on the preceding paragraphs wherein said lipid acyltransferase is a polypeptide having lipid acyltranferase activity which polypeptide is obtained by expression of any one of the nucleotide sequences shown as SEQ ID NO: 36, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 or SEQ ID NO: 63 or a nucleotide sequence which as has 75% or more identity therewith.

9. A method according to any one of the preceding paragraphs wherein said lipid acyltranferase is a polypeptide having lipid acyltranferase activity which polypeptide is obtained by expression of:

    
    
        a) the nucleotide sequence shown as SEQ ID NO: 49 or a nucleotide sequence which as has 75% or more identity therewith;
        b) a nucleic acid which encodes said polypeptide wherein said polypeptide is at least 70% identical with the polypeptide sequence shown in SEQ ID NO: 16 or with the polypeptide sequence shown in SEQ ID NO: 68;
        c) or a nucleic acid which hybridises under medium stringency conditions to a nucleic probe comprising the nucleotide sequence shown as SEQ ID NO: 49.

10. A method according to any on the preceding paragraphs wherein said lipid acyltransferase is a polypeptide having lipid acyltranferase activity which polypeptide comprises any one of the amino acid sequences shown as SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 68 or an amino acid sequence sequence which as has 75% or more identity therewith.

11. A method according to any one of the preceding paragraphs wherein said lipid acyltranferase is a polypeptide having lipid acyltranferase activity which polypeptide comprises the amino acid sequence shown as SEQ ID NO: 68 or an amino acid sequence sequence which as has 75% or more identity therewith.

12. Use of a lipid acyltransferase in the manufacture of UHT milk for improving the stability, particularly the long term stability, of the UHT milk.

Use of a lipid acyltransferase in the manufacture of UHT milk for improving the perceptible sensory difference of the UHT milk.

    
    


14. Use of a lipid acyltransferase in the manufacture of UHT milk for improving smell and/or taste of the UHT milk.
15. Use of a lipid acyltransferase in the manufacture of UHT milk for reducing the cholesterol content in the UHT milk.
16. Use of a lipid acyltransferase in the manufacture of UHT milk for eliminating or reducing creaming in the UHT milk.
17. Use according to any one of paragraphs 12-16 wherein the lipid acyltransferase is added to the UHT milk and incubated therewith at a temperature of less than about 20° C., preferably less than about 10° C.
18. Use according to any one of paragraphs 12-17 wherein the lipid acyltransferase is added to the UHT milk and incubated therewith at a temperature of between about 1° C. and about 10° C., preferably between about 3° C. and about 7° C., more preferably about 5° C.

19. Use according to any one of paragraphs 12 to 18 wherein the lipid acyltransferase comprises a GDSX (SEQ ID NO: 120) motif and/or a GANDY (SEQ ID NO: 118) motif.

20. Use according to any one of paragraphs 12-19 wherein the lipid acyltransferase enzyme is characterised as an enzyme which possesses acyltransferase activity and which comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S.

21. Use according to any one of paragraphs 12-20 wherein the lipid acyltransferase for use in any one of the methods and/or uses of the present invention may be obtainable, preferably obtained, from an organism from one or more of the following genera: Aeromonas, Streptomyces, Saccharomyces, Lactococcus, Mycobacterium, Streptococcus, Lactobacillus, Desulfitobacterium, Bacillus, Campylobacter, Vibrionaceae, Xylella, Sulfolobus, Aspergillus, Schizosaccharomyces, Listeria, Neisseria, Mesorhizobium, Ralstonia, Xanthomonas and Candida. 

22. Use according to paragraph 21 wherein the lipid acyltransferase is obtainable, preferably obtained, from an organism from the genus Aeromonas. 

23. Use according to any one of paragraphs 12-22 wherein said lipid acyltransferase is a polypeptide having lipid acyltransferase activity which polypeptide is obtained by expression of any one of the nucleotide sequences shown as SEQ ID NO: 36, SEQ ID NO: 38, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 or SEQ ID NO: 63 or a nucleotide sequence which as has 75% or more identity therewith.

24. Use according to any one of claims 12-23 wherein said lipid acyltransferase is a polypeptide having lipid acyltransferase activity which polypeptide is obtained by expression of:

    
    
        a. the nucleotide sequence shown as SEQ ID NO: 49 or a nucleotide sequence which as has 75% or more identity therewith;
        b. a nucleic acid which encodes said polypeptide wherein said polypeptide is at least 70% identical with the polypeptide sequence shown in SEQ ID NO: 16 or with the polypeptide sequence shown in SEQ ID NO: 68; or
        c. a nucleic acid which hybridises under medium stringency conditions to a nucleic probe comprising the nucleotide sequence shown as SEQ ID NO: 49.

25. Use according to any one of paragraphs 12-24 wherein said lipid acyltransferase is a polypeptide having lipid acyltransferase activity which polypeptide comprises any one of the amino acid sequences shown as SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34, SEQ ID NO: 35, SEQ ID NO: 68 or an amino acid sequence which as has 75% or more identity therewith.

26. Use according to any one of paragraphs 12-25 wherein said lipid acyltransferase is a polypeptide having lipid acyltransferase activity which polypeptide comprises the amino acid sequence shown as SEQ ID NO: 68 or an amino acid sequence which as has 75% or more identity therewith.

27. A method according to any one of paragraphs 9-11 wherein the polypeptide is obtained by expression in Bacillus licheniformis. 

28. A use according to any one of paragraphs 24-26 wherein the polypeptide is obtained by expression in Bacillus licheniformis. 

29. A method as generally defined herein with reference to the examples and figures.

30. A use as generally defined herein with reference to the examples and figures.

## Claims

1. A method of producing ultra-heat treatment (UHT) milk comprising: mixing a lipid acyltransferase with milk, or a milk fraction, and heating mixture with an ultra-heat treatment to thereby produce UHT milk,
wherein the lipid acyltransferase has at least 5% transferase activity when calculated with an assay for transferase activity,
wherein the assay comprises measuring a molar amount of cholesterol ester formed by acyltransfer from phospholipids or triacylglycerides in milk to cholesterol relative to the amount of cholesterol originally available with a formula:


Transferase activity=(Mol/l cholesterol ester(t)−Mol/l cholesterol ester(0))×100 Mol/l cholesterol(0); and


wherein cholesterol ester(t)=the amount of cholesterol ester to the time t,
Cholesterol ester(0)=the amount of cholesterol ester to the time 0,
Cholesterol (0)=the amount of cholesterol in milk to the time 0 and
Cholesterol and cholesterol ester are determined by gas liquid chromatography (GLC).

2. The method of claim 1, wherein the lipid acyltransferase is added prior to ultra-heat treatment or after ultra-heat treatment.

3. The method of claim 1, wherein the mixture is incubated at a temperature of less than about 20° C.

4. The method of claim 1, wherein the mixture is incubated at a temperature of between about 1° C. and about 10° C.

5. The method of claim 1, wherein the lipid acyltransferase comprises the amino acid sequence motif GDSX (SEQ ID NO: 120) and/or GANDY (SEQ ID NO: 118).

6. The method of claim 1, wherein the lipid acyltransferase possesses acyltransferase activity and comprises the amino acid sequence motif GDSX (SEQ ID NO: 117), wherein X is one or more of the following amino acid residues L, A, V, I, F, Y, H, Q, T, N, M or S.

7. The method of claim 1, wherein the lipid acyltransferase is from an organism in a genera selected from the group consisting of: Aeromonas, Streptomyces, Saccharomyces, Lactococcus, Mycobacterium, Streptococcus, Lactobacillus, Desulfitobacterium, Bacillus, Campylobacter, Vibrionaceae, Xylella, Sulfolobus, Aspergillus, Schizosaccharomyces, Listeria, Neisseria, Mesorhizobium, Ralstonia, Xanthomonas and Candida.

8. The method of claim 7, wherein the lipid acyltransferase is from an organism from the genus Aeromonas.

9. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and is produced by expressing a nucleotide sequence selected from the group consisting of: SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 and SEQ ID NO: 63.

10. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and is produced by expressing a nucleotide sequence having 90% or more identity with a nucleotide sequence selected from the group consisting of: SEQ ID NO: 36, SEQ ID NO: 39, SEQ ID NO: 42, SEQ ID NO: 44, SEQ ID NO: 46, SEQ ID NO: 48, SEQ ID NO: 49, SEQ ID NO: 50, SEQ ID NO: 51, SEQ ID NO: 52, SEQ ID NO: 53, SEQ ID NO: 54, SEQ ID NO: 55, SEQ ID NO: 56, SEQ ID NO: 57, SEQ ID NO: 58, SEQ ID NO: 59, SEQ ID NO: 60, SEQ ID NO: 61, SEQ ID NO: 62 and SEQ ID NO: 63.

11. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and is produced by expressing:
SEQ ID NO: 49 or a nucleotide sequence having 90% or more identity therewith;
a nucleic acid encoding a polypeptide having at least 90% identity with SEQ ID NO: 16 or with SEQ ID NO: 68, or
a nucleic acid which hybridises under high stringency conditions (65° C. and 0.1.times.SSC {1×SSC=0.15 M NaCl, 0.015 M Na-citrate pH 7.0}) to a probe comprising SEQ ID NO: 49.

12. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and comprises an amino acid sequence selected from the group consisting of: SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34, SEQ ID NO: 35 and SEQ ID NO: 68.

13. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and comprises an amino acid sequence having 90% or more identity with an amino acid sequence selected from the group consisting of: SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 4, SEQ ID NO: 5, SEQ ID NO: 6, SEQ ID NO: 7, SEQ ID NO: 8, SEQ ID NO: 9, SEQ ID NO: 10, SEQ ID NO: 11, SEQ ID NO: 12, SEQ ID NO: 13, SEQ ID NO: 14, SEQ ID NO: 15, SEQ ID NO: 17, SEQ ID NO: 16, SEQ ID NO: 17, SEQ ID NO: 18, SEQ ID NO: 34, SEQ ID NO: 35 and SEQ ID NO: 68.

14. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and comprises SEQ ID NO: 68.

15. The method of claim 1, wherein the lipid acyltransferase is a polypeptide having lipid acyltransferase activity and comprises an amino acid sequence having 90% or more identity with SEQ ID NO: 68.

16. The method of claim 11, wherein the polypeptide is expressed in Bacillus licheniformis.

17. The method of claim 3, wherein the mixture is incubated at a temperature of less than about 10° C.

18. The method of claim 4, wherein the mixture is incubated at a between about 3° C. and about 7° C.

19. The method of claim 18, wherein the mixture is incubated at about 5° C.