Patent Publication Number: US-10329590-B2

Title: Method of producing nylon

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is US national stage of international application PCT/EP2015/059786, which had an international filing date of May 5, 2015, and which was published in English on Nov. 19, 2015. Priority is claimed to European application EP 14168174.2, filed on May 13, 2014. The contents of the priority application is hereby incorporated by reference in its entirety. 
     SUMMARY OF THE INVENTION 
     The present invention relates to the biotechnological production of polyamides, in particular nylon from synthesis gas which is converted to hexanoic acid and then chemically converted to methyl hexanoate which is then contacted with cells that convert the methyl hexanoate to aminohexanoic acid and/or esters thereof. 
     BACKGROUND OF THE INVENTION 
     Polyamides are synthetic polymers where the repeating units (monomers) possess the amide group as a characteristic feature. The designation “polyamides” is usually used to designate synthetic, commercially usable thermoplastics and therefore demarcates this class of substances from the chemically related proteins. Nearly all the important polyamides are derived from primary amines, i.e. the functional group —CO—NH— occurs in their repeat units. Polyamides of secondary amines (—CO—NR—, R=organic residue) also exist. Aminocarboxylic acids, lactams and/or diamines and dicarboxylic acids in particular find application as monomers for the polyamides. 
     When the repeating units between the amide linkages are substantially aliphatic, they form polyamide polymers that are called nylon. Nylon is known to be made through the condensation reaction between a diamine and a diacid. Nylon is one of the most widely used polymers because of its characteristics. In particular, nylon is highly resilient and durable. Nylon fibres are thus used in many applications, including clothes fabrics, package paper, carpets, musical strings, pipes, rope, mechanical parts and the like. 
     Some commonly available nylon polymers include but are not limited to nylon 6,6, nylon 6, nylon 11, nylon 12, nylon 4,6, nylon 6,12, nylon 6,10 and the like. Out of which, nylon 6,6 and nylon 6 are the more commonly used polymers. Nylon may be made through step-growth polymerisation or chain-growth polymerisation. Making nylon from a diamine and a diacid or an amino acid is a step-growth polymerisation whereas making nylon from lactams usually involves a chain-growth polymerisation. Since the latter method starts off with monomers, the monomers quickly form high molecular weight polymers making the process of polymerisation more efficient. This method also reduces the formation of intermediate dimers, trimers, and other oligomers. This method is thus more favoured than step-growth polymerisation. 
     Caprolactam is the feedstock in the production of nylon 6 using chain-growth polymerisation. The production of caprolactam is usually carried out by reacting cyclohexanone with hydrogensulphate or hydrochloride of hydroxylamine resulting in the formation of cyclohexanone oxime. This is then converted by a Beckmann rearrangement into caprolactam, often with the use of concentrated sulphuric acid as catalyst. The raw material, cyclohexanone is usually produced by catalytic oxidation of cyclohexane with oxygen of the air and cyclohexane is in turn obtained by hydrogenation of benzene. 
     There are several disadvantages with the currently available methods of producing nylon. One disadvantage in the production of lactams by Beckmann rearrangement of oximes is, among other things, that large amounts of salts, for example sodium sulphate, are formed as by-product, which requires disposal. Other methods for the production of lactams described in the prior art which use a different method include EP0748797 which describes a method of production of lactams from dinitriles, in which the dinitrile is hydrogenated to aminonitrile and the aminonitrile is converted by cyclizing hydrolysis to the lactam. Molecular sieves, such as acid zeolites, silicates and non-zeolitic molecular sieves, metal phosphates and metal oxides or mixed metal oxides were used as catalyst for cyclizing hydrolysis. However, this method has, among other drawbacks, the disadvantage that the selectivity of the conversion of the aminonitrile by cyclizing hydrolysis is rather low and therefore large amounts of by-products are also formed. 
     Further, the traditional manufacture of nylon uses petroleum based intermediates. For example, cyclohexane is used to make adipic acid and caprolactam. Butadiene and natural gas are important raw materials for making hexamethylene diamine. Nylon 12 is also dependent upon butadiene feedstocks. Thus, in most methods of producing lactams described in the prior art, hydrocarbons such as benzene or butadiene are used, and these are obtained by cracking gasoline or petroleum which is bad for the environment. Also, since the costs for these starting materials will be linked to the price of petroleum, with the expected increase in petroleum prices in the future, nylon prices may also increase relative to the increase in the petroleum prices. 
     Accordingly, it is desirable to find more sustainable raw materials, other than purely petroleum based, as starting materials for nylon production which also cause less damage to the environment. 
     DESCRIPTION OF THE INVENTION 
     There is provided a method of producing aminohexanoic acid and/or aminohexanoic acid ester from synthesis gas, the method comprising:
         A. contacting the synthesis gas with at least one acetogenic bacteria and/or hydrogen oxidising bacteria to produce hexanoic acid; and   B. contacting the hexanoic acid with a genetically modified cell to produce aminohexanoic acid and/or aminohexanoic acid ester, wherein the genetically modified cell has an increased activity, in comparison with its wild type, of at least one enzyme selected from the group consisting of alkane monooxygenase, alcohol dehydrogenase, and ω-transaminase.       

     In particular, according to any aspect of the present invention, there is provided a method of producing aminohexanoic acid and/or aminohexanoic acid ester from synthesis gas, the method comprising:
         A. contacting the synthesis gas with at least one bacteria capable of carrying out the Wood-Ljungdahl pathway and/or the ethanol-carboxylate fermentation to produce hexanoic acid; and   B. contacting the hexanoic acid with a genetically modified cell to produce aminohexanoic acid and/or aminohexanoic acid ester, wherein the genetically modified cell has an increased activity, in comparison with its wild type, of alkane monooxygenase, alcohol dehydrogenase, and ω-transaminase.       

     Usually, a portion of the synthesis gas obtained from the gasification process is first processed in order to optimize product yields, and to avoid formation of tar. Cracking of the undesired tar and CO in the synthesis gas may be carried out using lime and/or dolomite. These processes are described in detail in for example, Reed, 1981. 
     The synthesis gas may be converted to hexanoic acid in the presence of at least one acetogenic bacteria and/or hydrogen oxidising bacteria. In particular, any method known in the art may be used. Hexanoic acid may be produced from synthesis gas by at least one prokaryote. In particular, the prokaryote may be selected from the group consisting of the genus  Escherichia  such as  Escherichia coli ; from the genus  Clostridia  such as  Clostridium ljungdahlii, Clostridium autoethanogenum, Clostridium carboxidivorans  or  Clostridium kluyveri ; from the genus  Corynebacteria  such as  Corynebacterium glutamicum ; from the genus  Cupriavidus  such as  Cupriavidus necator  or  Cupriavidus metallidurans ; from the genus  Pseudomonas  such as  Pseudomonas fluorescens, Pseudomonas putida  or  Pseudomonas oleavorans ; from the genus  Delftia  such as  Delftia acidovorans ; from the genus  Bacillus  such as  Bacillus subtillis ; from the genus  Lactobacillus  such as  Lactobacillus delbrueckii ; or from the genus  Lactococcus  such as  Lactococcus lactis.    
     In another example, hexanoic acid may be produced from synthesis gas by at least one eukaryote. The eukaryote used in the method of the present invention may be selected from the genus  Aspergillus  such as  Aspergillus niger ; from the genus  Saccharomyces  such as  Saccharomyces cerevisiae ; from the genus  Pichia  such as  Pichia pastoris ; from the genus  Yarrowia  such as  Yarrowia lipolytica ; from the genus  Issatchenkia  such as  Issathenkia orientalis ; from the genus  Debaryomyces  such as  Debaryomyces hansenii ; from the genus  Arxula  such as  Arxula adenoinivorans ; or from the genus  Kluyveromyces  such as  Kluyveromyces lactis.    
     More in particular, hexanoic acid may be produced from synthesis gas by any method disclosed in Steinbusch, 2011, Zhang, 2013, Van Eerten-Jansen, M. C. A. A, 2013, Ding H. et al, 2010, Barker H. A., 1949, Stadtman E. R., 1950, Bornstein B. T., et al., 1948 and the like. Even more in particular, the hexanoic acid may be produced from synthesis gas in the presence of at least  Clostridium kluyveri.    
     The term “acetogenic bacteria” as used herein refers to a microorganism which is able to perform the Wood-Ljungdahl pathway and thus is able to convert CO, CO 2  and/or hydrogen to acetate. These microorganisms include microorganisms which in their wild-type form do not have a Wood-Ljungdahl pathway, but have acquired this trait as a result of genetic modification. Such microorganisms include but are not limited to  E. coli  cells. These microorganisms may be also known as carboxydotrophic bacteria. Currently, 21 different genera of the acetogenic bacteria are known in the art (Drake et al., 2006), and these may also include some  clostridia  (Drake &amp; Kusel, 2005). These bacteria are able to use carbon dioxide or carbon monoxide as a carbon source with hydrogen as an energy source (Wood, 1991). Further, alcohols, aldehydes, carboxylic acids as well as numerous hexoses may also be used as a carbon source (Drake et al., 2004). The reductive pathway that leads to the formation of acetate is referred to as acetyl-CoA or Wood-Ljungdahl pathway. In particular, the acetogenic bacteria may be selected from the group consisting of  Acetoanaerobium notera  (ATCC 35199),  Acetonema longum  (DSM 6540),  Acetobacterium carbinolicum  (DSM 2925),  Acetobacterium malicum  (DSM 4132),  Acetobacterium  species no. 446 (Morinaga et al., 1990 , J. Biotechnol ., Vol. 14, p. 187-194),  Acetobacterium wieringae  (DSM 1911),  Acetobacterium woodii  (DSM 1030),  Alkalibaculum bacchi  (DSM 22112),  Archaeoglobus fulgidus  (DSM 4304),  Blautia producta  (DSM 2950, formerly  Ruminococcus productus , formerly  Peptostreptococcus productus ),  Butyribacterium methylotrophicum  (DSM 3468),  Clostridium aceticum  (DSM 1496),  Clostridium autoethanogenum  (DSM 10061, DSM 19630 and DSM 23693),  Clostridium carboxidivorans  (DSM 15243),  Clostridium coskatii  (ATCC no. PTA-10522),  Clostridium drakei  (ATCC BA-623),  Clostridium formicoaceticum  (DSM 92),  Clostridium glycolicum  (DSM 1288),  Clostridium ljungdahlii  (DSM 13528),  Clostridium ljungdahlii  C-01 (ATCC 55988),  Clostridium ljungdahlii  ERI-2 
     (ATCC 55380),  Clostridium ljungdahlii  O-52 (ATCC 55989),  Clostridium mayombei  (DSM 6539),  Clostridium methoxybenzovorans  (DSM 12182),  Clostridium ragsdalei  (DSM 15248),  Clostridium scatologenes  (DSM 757),  Clostridium  species ATCC 29797 (Schmidt et al., 1986 , Chem. Eng. Commun ., Vol. 45, p. 61-73),  Desulfotomaculum kuznetsovii  (DSM 6115),  Desulfotomaculum thermobezoicum  subsp.  thermosyntrophicum  (DSM 14055),  Eubacterium limosum  (DSM 20543),  Methanosarcina acetivorans  C2A (DSM 2834),  Moorella  sp. HUC22-1 (Sakai et al., 2004 , Biotechnol. Let ., Vol. 29, p. 1607-1612),  Moorella thermoacetica  (DSM 521, formerly  Clostridium thermoaceticum ),  Moorella thermoautotrophica  (DSM 1974),  Oxobacter pfennigii  (DSM 322),  Sporomusa aerivorans  (DSM 13326),  Sporomusa ovata  (DSM 2662),  Sporomusa silvacetica  (DSM 10669),  Sporomusa sphaeroides  (DSM 2875),  Sporomusa termitida  (DSM 4440) and  Thermoanaerobacter kivui  (DSM 2030, formerly  Acetogenium kivui ). 
     More in particular, the strain ATCC BAA-624 of  Clostridium carboxidivorans  may be used. Even more in particular, the bacterial strain labelled “P7” and “P11” of  Clostridium carboxidivorans  as described for example in U.S. 2007/0275447 and U.S. 2008/0057554 may be used. 
     Another particularly suitable bacterium may be  Clostridium ljungdahlii . In particular, strains selected from the group consisting of  Clostridium ljungdahlii  PETC,  Clostridium ljungdahlii  ERI2,  Clostridium ljungdahlii  COL and  Clostridium ljungdahlii  0-52 may be used in the conversion of synthesis gas to hexanoic acid. These strains for example are described in WO 98/00558, WO 00/68407, ATCC 49587, ATCC 55988 and ATCC 55989. 
     The acetogenic bacteria may be used in conjunction with a hydrogen oxidising bacteria. In one example, both an acetogenic bacteria and a hydrogen oxidising bacteria may be used to produce hexanoic acid from synthesis gas. In another example, only acetogenic bacteria may be used for metabolising synthesis gas to produce hexanoic acid from synthesis gas. In yet another example, only a hydrogen oxidising bacteria may be used in this reaction. 
     The hydrogen oxidising bacteria may be selected from the group consisting of  Achromobacter, Acidithiobacillus, Acidovorax, Alcaligenes, Anabena, Aquifex, Arthrobacter, Azospirillum, Bacillus, Bradyrhizobium, Cupriavidus, Derxia, Helicobacter, Herbaspirillum, Hydrogenobacter, Hydrogenobaculum, Hydrogenophaga, Hydrogenophilus, Hydrogenothermus, Hydrogenovibrio, Ideonella  sp. O1 , Kyrpidia, Metallosphaera, Methanobrevibacter, Myobacterium, Nocardia, Oligotropha, Paracoccus, Pelomonas, Polaromonas, Pseudomonas, Pseudonocardia, Rhizobium, Rhodococcus, Rhodopseudomonas, Rhodospirillum, Streptomyces, Thiocapsa, Treponema, Variovorax, Xanthobacter  and  Wautersia.    
     In the production of hexanoic acid from synthesis gas a combination of bacteria may be used. There may be more than one acetogenic bacteria present in combination with one or more hydrogen oxidising bacteria. In another example, there may be more than one type of acetogenic bacteria present only. In yet another example, there may more than one hydrogen oxidising bacteria present only. Hexanoic acid also known as caproic acid has general formula C 5 H 11 COOH. 
     The method according to any aspect of the present invention may further comprise the step of esterification of the hexanoic acid of step A to produce a C 1 -C 4  hexanoate and the C 1 -C 4  hexanoate is contacted with the genetically modified cell of step B. In particular, the method of esterification involves contacting the hexanoic acid of step A with at least one C 1 -C 4  alcohol to produce C 1 -C 4  hexanoate. 
     In another example, the production of hexanoic acid from synthesis gas may involve the use of the acetogenic bacteria in conjunction with a bacterium capable of producing the hexanoic acid using ethanol-carboxylate fermentation hydrogen oxidising bacteria. In one example, both an acetogenic bacteria and a hydrogen oxidising bacteria may be used to produce hexanoic acid from synthesis gas. For example,  Clostridium ljungdahlii  may be used simultaneously with  Clostridium kluyveri . In another example, only acetogenic bacteria may be used for metabolising synthesis gas to produce hexanoic acid from synthesis gas. In this example, the acetogenic bacteria may be capable of carrying out both the ethanol-carboxylate fermentation pathway and the Wood-Ljungdahl pathway. In one example, the acetogenic bacteria may be  C. carboxidivorans  which may be capable of carrying out both the Wood-Ljungdahl pathway and the ethanol-carboxylate fermentation pathway. 
     The ethanol-carboxylate fermentation pathway is described in detail at least in Seedorf, H., et al., 2008. The organism may be selected from the group consisting of  Clostridium kluyveri, C. Carboxidivorans  and the like. These microorganisms include microorganisms which in their wild-type form do not have an ethanol-carboxylate fermentation pathway, but have acquired this trait as a result of genetic modification. In particular, the microorganism may be  Clostridium kluyveri.    
     In one example, the cell carrying out step A according to any aspect of the present invention may be a genetically modified microorganism. The genetically modified cell or microorganism may be genetically different from the wild type cell or microorganism. The genetic difference between the genetically modified microorganism according to any aspect of the present invention and the wild type microorganism may be in the presence of a complete gene, amino acid, nucleotide etc. in the genetically modified microorganism that may be absent in the wild type microorganism. In one example, the genetically modified microorganism according to any aspect of the present invention may comprise enzymes that enable the microorganism to produce hexanoic acid. The wild type microorganism relative to the genetically modified microorganism of the present invention may have none or no detectable activity of the enzymes that enable the genetically modified microorganism to produce the hexanoic acid. As used herein, the term ‘genetically modified microorganism’ may be used interchangeably with the term ‘genetically modified cell’. The genetic modification according to any aspect of the present invention is carried out on the cell of the microorganism. 
     In one example, the microorganism may be a wild type organism that expresses at least one enzyme selected E 1  to E 10 , wherein E 1  is an alcohol dehydrogenase (adh), E 2  is an acetaldehyde dehydrogenase (aid), E 3  is an acetoacetyl-CoA thiolase (thl), E 4  is a 3-hydroxybutyryl-CoA dehydrogenase (hbd), E 5  is a 3-hydroxybutyryl-CoA dehydratase (crt), E 6  is a butyryl-CoA dehydrogenase (bcd), E 7  is an electron transfer flavoprotein subunit (etf), E 8  is a coenzyme A transferase (cat), E 9  is an acetate kinase (ack) and E 10  is phosphotransacetylase (pta). In particular, the wild type microorganism according to any aspect of the present invention may express at least E 2 , E 3  and E 4 . Even more in particular, the wild type microorganism according to any aspect of the present invention may express at least E 4 . 
     In another example, the microorganism according to any aspect of the present invention may be a genetically modified organism that has increased expression relative to the wild type microorganism of at least one enzyme selected E 1  to E 10 , wherein E 1  is an alcohol dehydrogenase (adh), E 2  is an acetaldehyde dehydrogenase (aid), E 3  is an acetoacetyl-CoA thiolase (thl), E 4  is a 3-hydroxybutyryl-CoA dehydrogenase (hbd), E 5  is a 3-hydroxybutyryl-CoA dehydratase (crt), E 6  is a butyryl-CoA dehydrogenase (bcd), E 7  is an electron transfer flavoprotein subunit (etf), E 8  is a coenzyme A transferase (cat), E 9  is an acetate kinase (ack) and E 10  is phosphotransacetylase (pta). In particular, the genetically modified microorganism according to any aspect of the present invention may express at least enzymes E 2 , E 3  and E 4 . Even more in particular, the genetically modified microorganism according to any aspect of the present invention may express at least E 4 . The enzymes E 1  to E 10  may be isolated from  Clostridium kluyveri.    
     According to any aspect of the present invention, E 1  may be an ethanol dehydrogenase. In particular, E 1  may be selected from the group consisting of alcohol dehydrogenase 1, alcohol dehydrogenase 2, alcohol dehydrogenase 3, alcohol dehydrogenase B and combinations thereof. More in particular, E 1  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_1075, CKL_1077, CKL_1078, CKL_1067, CKL_2967, CKL_2978, CKL_3000, CKL_3425, and CKL_2065. Even more in particular, E 1  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_1075, CKL_1077, CKL_1078 and CKL_1067. 
     According to any aspect of the present invention, E 2  may be an acetaldehyde dehydrogenase. In particular, E 2  may be selected from the group consisting of acetaldehyde dehydrogenase 1, alcohol dehydrogenase 2 and combinations thereof. In particular, E 2  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_1074, CKL_1076 and the like. More in particular, E 2  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_1074 and CKL_1076. 
     According to any aspect of the present invention, E 3  may be selected from the group consisting of acetoacetyl-CoA thiolase A1, acetoacetyl-CoA thiolase A2, acetoacetyl-CoA thiolase A3 and combinations thereof. In particular, E 3  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_3696, CKL_3697, CKL_3698 and the like. More in particular, E 3  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_3696, CKL_3697 and CKL_3698. 
     According to any aspect of the present invention, E 4  may be 3-hydroxybutyryl-CoA dehydrogenase 1, 3-hydroxybutyryl-CoA dehydrogenase 2 and the like. In particular, E 4  may comprise sequence identity of at least 50% to a polypeptide CKL_0458, CKL_2795 and the like. More in particular, E 4  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to the polypeptide CKL_0458 or CKL_2795. 
     According to any aspect of the present invention, E 5  may be 3-hydroxybutyryl-CoA dehydratase 1, 3-hydroxybutyryl-CoA dehydratase 2 and combinations thereof. In particular, E 5  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_0454, CKL_2527 and the like. More in particular, E 5  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_0454 and CKL_2527. 
     According to any aspect of the present invention, E 6  may be selected from the group consisting of butyryl-CoA dehydrogenase 1, butyryl-CoA dehydrogenase 2 and the like. In particular, E 6  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_0455, CKL_0633 and the like. More in particular, E 6  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_0455 and CKL_0633. 
     According to any aspect of the present invention, E 7  may be selected from the group consisting of electron transfer flavoprotein alpha subunit 1, electron transfer flavoprotein alpha subunit 2, electron transfer flavoprotein beta subunit 1 and electron transfer flavoprotein beta subunit 2. In particular, E 7  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_3516, CKL_3517, CKL_0456, CKL_0457 and the like. More in particular, E 7  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_3516, CKL_3517, CKL_0456 and CKL_0457. 
     According to any aspect of the present invention, E 8  may be coenzyme transferase (cat). In particular, E 8  may be selected from the group consisting of butyryl-CoA: acetate CoA transferase, succinyl-CoA:coenzyme A transferase, 4-hydroxybutyryl-CoA: coenzyme A transferase and the like. More in particular, E 8  may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_3595, CKL_3016, CKL_3018 and the like. More in particular, E 8  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_3595, CKL_3016 and CKL_3018. 
     According to any aspect of the present invention, E 9  may be an acetate kinase A (ack A). In particular, E 9  may comprise sequence identity of at least 50% to a polypeptide sequence of CKL_1391 and the like. More in particular, E 9  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide of CKL_1391. 
     According to any aspect of the present invention, E 10  may be phosphotransacetylase (pta). In particular, E 10  may comprise sequence identity of at least 50% to a polypeptide sequence of CKL_1390 and the like. More in particular, E 10  may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide of CKL_1390. 
     In one example the microorganism, wild-type or genetically modified expresses E 1 -E 10 . In particular, the microorganism according to any aspect of the present invention may have increased expression relative to the wild type microorganism of E 1 , E 2 , E 3 , E 4 , E 5 , E 6 , E 7 , E 8 , E 9 , E 10  or combinations thereof. In one example, the genetically modified microorganism has increased expression relative to the wild type microorganism of E 1 , E 2 , E 3 , E 4 , E 5 , E 6 , E 7 , E 8 , E 9  and E 10 . More in particular, a combination of any of the enzymes E 1 -E 10  may be present in the organism to enable at least one carboxylic acid to be produced. In one example, the genetically modified organism used according to any aspect of the present invention may comprise a combination of any of the enzymes E 1 -E 10  that enable the organism to produce at least one, or two or three types of carboxylic acids at the same time. For example, the microorganism may be able to produce hexanoic acid, butyric acid and/or acetic acid at the simultaneously. Similarly, the microorganism may be genetically modified to express a combination of enzymes E 1 -E 10  that enable the organism to produce either a single type of carboxylic acid or a variety of carboxylic acids. In all the above cases, the microorganism may be in its wild-type form or be genetically modified. 
     In one example, the genetically modified microorganism according to any aspect of the present invention has increased expression relative to the wild type microorganism of hydrogenase maturation protein and/or electron transport complex protein. In particular, the hydrogenase maturation protein (hyd) may be selected from the group consisting of hydE, hydF or hydG. In particular, the hyd may comprise sequence identity of at least 50% to a polypeptide selected from the group consisting of CKL_0605, CKL_2330, CKL_3829 and the like. More in particular, the hyd used according to any aspect of the present invention may comprise a polypeptide with sequence identity of at least 50, 60, 65, 70, 75, 80, 85, 90, 91, 94, 95, 98 or 100% to a polypeptide selected from the group consisting of CKL_0605, CKL_2330 and CKL_3829. 
     Throughout this application, any data base code, unless specified to the contrary, refers to a sequence available from the NCBI data bases, more specifically the version online on 12 Jun. 2014, and comprises, if such sequence is a nucleotide sequence, the polypeptide sequence obtained by translating the former. 
     The method according to any aspect of the present invention, may further comprise the step of esterification of the hexanoic acid of step A to produce a C 1 -C 4  hexanoate and the C 1 -C 4  hexanoate is contacted with the genetically modified cell of step B. 
     In one example, the method of esterification may be a chemical process. Any chemical reaction known in the art may be used to convert hexanoic acid to C 1 -C 4  alcohol hexanoate. More in particular, the method involves reacting hexanoic acid with an alcohol. Hexanoic acid may be contacted with at least one short-chained carbon alcohol to produce a hexanoate. In particular, the short-chained carbon alcohol may be a C 1 -C 4  alcohol. The short chain alcohol may be methanol, ethanol, isopropyl alcohol, and/or butyl alcohol. In particular, the alcohol may be selected from the group consisting of methanol, ethanol, isopropyl alcohol, and/or butyl alcohol to produce methyl, ethyl, propyl or butyl hexanoate respectively. This reaction may take place in the presence of at least one catalyst. The catalyst is usually an acidic catalyst such as s sulphonic acid, a base such as an alkali hydroxide or an alkali alcoholate, a metal oxide or a metal alkylate. In particular, hexanoic acid may be metabolised to form C1-C4 alcohol hexanoate. In particular, the catalyst may be ZrOCl 2 .8H 2 O. 
     In one example, the hexanoic acid reacts with methanol in the presence of ZrOCl 2 .8H 2 O to produce methyl hexanoate. 
     The method according to any aspect of the present invention may comprise a step of extracting the hexanoic acid produced from the synthesis gas first before contacting the hexanoic acid with at least one C 1 -C 4  alcohol. Any method known in the art for extracting hexanoic acid may be used. In particular, one example of an extraction method of hexanoic acid is provided in section 2.3 of Byoung, S. J et al. 2013. Another example may the method disclosed under the section ‘Extraction Model’ in Kieun C., Et al., 2013. 
     In another example, the method of esterification may be a biochemical process where at least one enzyme may be involved in catalysing the esterification process. The enzyme for esterification may be selected from the group consisting of a thioesterase enzyme, an acyl-CoA synthetase enzyme, an ester synthase enzyme and a lipase. At least one of these enzymes may be expressed in the bacteria of step A of the method of the present invention. In one example, the acetogenic bacteria and/or hydrogen oxidising bacteria may overexpress an esterification enzyme that may be capable of esterification of the hexanoic acid. In another example, a further cell expressing an esterification enzyme may be included after step A of the method of the present invention to esterify the hexanoic acid to a hexanoate. 
     The hexanoic acid from step A of the method of the present invention may be directly converted to aminohexanoic acid and/or aminohexanoic acid ester. In another example, the hexanoic acid from step A of the method of the present invention may first be esterified to a hexanoate either chemically or biochemically. This hexanoate is then contacted with the genetically modified cell of step B of the method of the present invention. In one example, both a chemical and biochemical process is carried out in combination sequentially or simultaneously to esterify the hexanoic acid. 
     The C 1 -C 4  alcohol hexanoate may then be contacted with a genetically modified cell to produce an aminohexanoic acid and/or aminohexanoic acid ester, wherein the genetically modified cell has an increased activity, in comparison with its wild type, of at least one enzyme selected from the group consisting of alkane monooxygenase, alcohol dehydrogenase, and ω-transaminase. 
     The cell according to any aspect of the present invention has been genetically modified relative to its wild type so that, in comparison with its wild type, it is able to produce more aminohexanoic acids and/or aminohexanoic acid esters, starting from C 1  to C 4  alcohol hexanoate. Such a cell may be used to produce aminohexanoic acids and/or aminohexanoic acid esters from aminohexanoic acids by fermentation from C 1  to C 4  alcohol hexanoate. 
     The phrase “that in comparison with its wild type it is able to produce more aminohexanoic acids and/or aminohexanoic acid esters, starting from methyl hexanoate” also applies to the case when the wild type of the genetically modified cell is not able to form any aminohexanoic acid, and/or aminohexanoic acid ester to begin with. Also included are wild type cells that produce at least no detectable amounts of these compounds and it is only after the genetic modification of the wild type to produce the cell used in any method of the present invention are there detectable amounts of these compounds formed. 
     The phrase “wild type” as used herein in conjunction with a cell may denote a cell with a genome make-up that is in a form as seen naturally in the wild. The term may be applicable for both the whole cell and for individual genes. The term “wild type” therefore does not include such cells or such genes where the gene sequences have been altered at least partially by man using recombinant methods. 
     In particular, the genetically modified cell may have been genetically modified so that in a defined time interval, for example within 2 hours, particularly within 8 hours and more particularly within 24 hours, it forms at least twice, in particular at least 10 times, more in particular at least 100, 1000 or 10000 times more aminohexanoic acids and/or aminohexanoic acid esters than the wild-type cell. The increase in product formation can be determined for example by cultivating the cell used according to the method of the invention and the wild-type cell each separately under the same conditions (same cell density, same nutrient medium, same culture conditions) for a specified time interval in a suitable nutrient medium and then determining the amount of target product (aminohexanoic acids and/or aminohexanoic acid esters) in the nutrient medium. 
     The cells used according to the method of the invention can be prokaryotes or eukaryotes. They can be mammalian cells (such as human cells or non-human cells), plant cells or microorganisms such as yeasts, fungi or bacteria. In particular, the microorganisms may be bacteria. More in particular, the microorganism may be yeasts. 
     Suitable bacteria, yeasts or fungi may be those bacteria, yeasts or fungi that have been deposited in the German Collection of Microorganisms and Cell Cultures (Deutsche Sammlung von Mikroorganismen and Zellkulturen GmbH, abbreviated to DSMZ), Brunswick, Germany, as strains of bacteria, yeasts or fungi. Suitable bacteria that may be used in the method of the invention may belong to the genera listed at www.dsmz.de/species/bacteria.htm. Suitable yeasts that may be used in the method of the invention belong to the genera listed at www.dsmz.de/species/yeasts.htm Suitable fungi that may be used in the method of the invention may belong to the genera listed at www.dsmz.de/species/fungi.htm. 
     In particular, the cells that may be genetically modified and used in the method of the present invention may be selected from the genera  Corynebacterium, Brevibacterium, Bacillus, Lactobacillus, Lactococcus, Candida, Pichia, Kluveromyces, Saccharomyces, Escherichia, Zymomonas, Yarrowia, Methylobacterium, Ralstonia, Pseudomonas, Burkholderia  and  Clostridium . More in particular, the cells that may be used in the method of the present invention may be selected from the group consisting of  Escherichia coli, Corynebacterium glutamicum  and  Pseudomonas putida . Even more in particular, the cells that may be used in the method of the present invention may be  Escherichia coli . The  E. coli  may be of any strain known in the art. In particular, the strain may be JM101. 
     In particular, in comparison with its wild type, increased activity of at least one of the following enzymes may be found in the genetically modified cell according to the method of the present invention:
         i) an alkane monooxygenase which catalyses the conversion of carboxylic acids or carboxylic acid esters to the corresponding ω-hydroxycarboxylic acids and/or ω-hydroxycarboxylic acid esters;   ii) an alcohol dehydrogenase which catalyses the conversion of ω-hydroxycarboxylic acids and/or ω-hydroxycarboxylic acid esters to the corresponding ω-oxocarboxylic acids or (ω-oxocarboxylic acid esters; and/or   iii) ω-transaminase which catalyses the conversion of ω-oxocarboxylic acids or ω-oxocarboxylic acid esters to the corresponding ω-aminocarboxylic acids or ω-aminocarboxylic acid esters.       

     The phrase “increased activity of an enzyme”, as used herein is to be understood as increased intracellular activity. Basically, an increase in enzymatic activity can be achieved by increasing the copy number of the gene sequence or gene sequences that code for the enzyme, using a strong promoter or employing a gene or allele that codes for a corresponding enzyme with increased activity and optionally by combining these measures. Genetically modified cells used in the method according to the invention are for example produced by transformation, transduction, conjugation or a combination of these methods with a vector that contains the desired gene, an allele of this gene or parts thereof and a vector that makes expression of the gene possible. Heterologous expression is in particular achieved by integration of the gene or of the alleles in the chromosome of the cell or an extrachromosomally replicating vector. 
     The cells according to any aspect of the present invention are genetically transformed according to any method known in the art. In particular, the cells may be produced according to the method disclosed in WO/2009/077461. 
     The phrase ‘the genetically modified cell has an increased activity, in comparison with its wild type, in enzymes’ as used herein refers to the activity of the respective enzyme that is increased by a factor of at least 2, in particular of at least 10, more in particular of at least 100, yet more in particular of at least 1000 and even more in particular of at least 10000. 
     According to any aspect of the present invention, the cell may have increase in activity of alkane monohydrogenase, alcohol dehydrogenase or ω-transaminase only or combinations thereof. In particular, the increase in activity may be in alkane monohydrogenase and alcohol dehydrogenase or alkane monohydrogenase, and ω-transaminase or alcohol dehydrogenase and ω-transaminase. In particular, the cell may have increase in activity of alkane monohydrogenase, alcohol dehydrogenase and ω-transaminase. 
     The enzyme alkane monooxygenase may be encoded by the AlkBGT gene from  Pseudomonas putida  GPO1. The isolation of the AlkBGT gene sequence is described for example in van Beilen et al., 2002. Furthermore, cytochrome P450 monoxygenases, in particular cytochrome P450 monoxygenases from  Candida , for example from  Candida tropicalis , or from plants, for example from the chick-pea ( Cicer arietinum  L.), can also be used as alkane monoxygenases. The gene sequences of suitable cytochrome P450 monoxygenases from  Candida tropicalis  are for example disclosed in WO00/20566, whereas the gene sequences of suitable cytochrome P450 monoxygenases from the chick-pea are given for example in Barz et al., 2000. Other homologues of the AlkB gene are also given in van Beilen et al., 2003. A suitable gene for a xylene monooxygenase is for example the xylM or the xylA gene, and a plasmid containing these two genes has the GENBANK Accession No. M37480. In particular, the gene sequence encoding alkane monoxygenase may be from  Pseudomonas oleovorans  and may comprise or may be the sequence of SEQ ID NO. 1 (Table 1). 
     The enzyme alcohol dehydrogenase may be encoded by the AlkJ gene (EC 1.1.99-2) from  Pseudomonas putida  GPO1,  Alcanivorax borkumensis, Bordetella parapertussis, Bordetella bronchiseptica  and  Roseobacter denitrificans . In particular, the AlkJ gene may be encoded by  Pseudomonas oleovorans . The gene sequences for the alcohol dehydrogenases encoded by the AlkJ gene can be found for example in the KEGG gene databank. In particular, the gene sequence encoding AlkJ gene may comprise or may be SEQ ID NO:2 (Table 1). 
     The enzyme ω-transaminase may be selected from the ω-transaminases that are characterized in US-A-2007/0092957 by the sequence numbers 248, 250, 252 and 254. 
     In another example, the ω-transaminases may be isolated from plants. The ω-transaminases from plants may be selected from the group consisting of  Arabidopsis thaliana, Avena sativa, Beta vulgaris, Glycine max, Hordeum vulgare, Lotus japonicus, Solanum lycopersicum, Manihot esculenta, Oryza sativa, Traeticum aestivum, Zea mays, Spinacia oleracea, Arum maculatum, Mercurialis perennis  and  Urtica dioica.    
     In particular, the ω-transaminase CV2025 from  Chromobacterium violaceum  DSM30191 may be used in the recombinant cell for the method of the present invention. More in particular, the ω-transaminase is the ω-transaminase from  Chromobacterium violaceum  DSM30191 (Kaulmann et al., 2007), which is encoded by the gene sequence according to SEQ ID NO:3 (Table 1). 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Nucleotide sequences of the genes used to 
               
               
                 genetically modify the cell according to any 
               
               
                 aspect of the present invention. 
               
            
           
           
               
               
            
               
                 SEQ 
                   
               
               
                 ID NO: 
                 nucleotide sequence 
               
               
                   
               
               
                 1 
                 CTTGAGAAACACAGAGTTCTGGATTCCGCTCCAGAGTACGTAGATAAAAAGAAATATCTC 
               
               
                   
                 TGGATACTATCAACTTTGTGGCCGGCTACTCCGATGATCGGAATCTGGCTTGCAAATGAA 
               
               
                   
                 ACTGGTTGGGGGATTTTTTATGGGCTGGTATTGCTCGTATGGTACGGCGCACTTCCATTG 
               
               
                   
                 CTTGATGCGATGTTTGGTGAGGACTTTAATAATCCGCCTGAAGAAGTGGTGCCGAAACTA 
               
               
                   
                 GAGAAGGAGCGGTACTATCGAGTTTTGACATATCTAACAGTTCCTATGCATTACGCTGCA 
               
               
                   
                 TTAATTGTGTCAGCATGGTGGGTCGGAACTCAGCCAATGTCTTGGCTTGAAATTGGTGCG 
               
               
                   
                 CTTGCCTTGTCACTGGGTATCGTGAACGGACTAGCGCTCAATACAGGACACGAACTCGGT 
               
               
                   
                 CACAAGAAGGAGACTTTTGATCGTTGGATGGCCAAAATTGTGTTGGCTGTCGTAGGGTAC 
               
               
                   
                 GGTCACTTCTTTATTGAGCATAATAAGGGTCATCACCGTGATGTCGCTACACCGATGGAT 
               
               
                   
                 CCTGCAACATCCCGGATGGGAGAAAGCATTTATAAGTTTTCAATCCGTGAGATCCCAGGA 
               
               
                   
                 GCATTTATTCGTGCTTGGGGGCTTGAGGAACAACGCCTTTCGCGCCGTGGCCAAAGCGTT 
               
               
                   
                 TGGAGTTTCGATAATGAAATCCTCCAACCAATGATCATCACAGTTATTCTTTACGCCGTT 
               
               
                   
                 CTCCTTGCCTTGTTTGGACCTAAGATGCTGGTGTTCCTGCCGATTCAAATGGCTTTCGGT 
               
               
                   
                 TGGTGGCAGCTGACCAGTGCGAACTATATTGAACATTACGGCTTGCTCCGTCAAAAAATG 
               
               
                   
                 GAGGACGGTCGATATGAGCATCAAAAGCCGCACCATTCTTGGAATAGTAATCACATCGTC 
               
               
                   
                 TCTAATCTAGTGCTGTTCCACCTTCAGCGGCACTCGGATCACCACGCGCATCCAACACGT 
               
               
                   
                 TCTTATCAGTCACTTCGGGATTTTCCCGGCCTGCCGGCTCTTCCGACGGGTTACCCTGGT 
               
               
                   
                 GCATTTTTGATGGCGATGATTCCTCAGTGGTTTAGATCAGTTATGGATCCCAAGGTAGTA 
               
               
                   
                 GATTGGGCTGGTGGTGACCTTAATAAGATCCAAATTGATGATTCGATGCGAGAAACCTAT 
               
               
                   
                 TTGAAAAAATTTGGCACTAGTAGTGCTGGTCATAGTTCGAGTACCTCTGCGGTAGCATCG 
               
               
                   
                 TAG 
               
               
                   
               
               
                 2 
                 ATGTACGACTATATAATCGTTGGTGCTGGATCTGCAGGATGTGTGCTTGCTAATCGTCTT 
               
               
                   
                 TCGGCCGACCCCTCTAAAAGAGTTTGTTTACTTGAAGCTGGGCCGCGAGATACGAATCCG 
               
               
                   
                 CTAATTCATATGCCGTTAGGTATTGCTTTGCTTTCAAATAGTAAAAAGTTGAATTGGGCT 
               
               
                   
                 TTTCAAACTGCGCCACAGCAAAATCTCAACGGCCGGAGCCTTTTCTGGCCACGAGGAAAA 
               
               
                   
                 ACGTTAGGTGGTTCAAGCTCAATCAACGCAATGGTCTATATCCGAGGGCATGAAGACGAT 
               
               
                   
                 TACCACGCATGGGAGCAGGCGGCCGGCCGCTACTGGGGTTGGTACCGGGCTCTTGAGTTG 
               
               
                   
                 TTCAAAAGGCTTGAATGCAACCAGCGATTCGATAAGTCCGAGCACCATGGGGTTGACGGA 
               
               
                   
                 GAATTAGCTGTTAGTGATTTAAAATATATCAATCCGCTTAGCAAAGCATTCGTGCAAGCC 
               
               
                   
                 GGCATGGAGGCCAATATTAATTTCAACGGAGATTTCAACGGCGAGTACCAGGACGGCGTA 
               
               
                   
                 GGGTTCTATCAAGTAACCCAAAAAAATGGACAACGCTGGAGCTCGGCGCGTGCATTCTTG 
               
               
                   
                 CACGGTGTACTTTCCAGACCAAATCTAGACATCATTACTGATGCGCATGCATCAAAAATT 
               
               
                   
                 CTTTTTGAAGACCGTAAGGCGGTTGGTGTTTCTTATATAAAGAAAAATATGCACCATCAA 
               
               
                   
                 GTCAAGACAACGAGTGGTGGTGAAGTACTTCTTAGTCTTGGCGCAGTCGGCACGCCTCAC 
               
               
                   
                 CTTCTAATGCTTTCTGGTGTTGGGGCTGCAGCCGAGCTTAAGGAACATGGTGTTTCTCTA 
               
               
                   
                 GTCCATGATCTTCCTGAGGTGGGGAAAAATCTTCAAGATCATTTGGACATCACATTGATG 
               
               
                   
                 TGCGCAGCAAATTCGAGAGAGCCGATAGGTGTTGCTCTTTCTTTCATCCCTCGTGGTGTC 
               
               
                   
                 TCGGGTTTGTTTTCATATGTGTTTAAGCGCGAGGGGTTTCTCACTAGTAACGTGGCAGAG 
               
               
                   
                 TCGGGTGGTTTTGTAAAAAGTTCTCCTGATCGTGATCGGCCCAATTTGCAGTTTCATTTC 
               
               
                   
                 CTTCCAACTTATCTTAAAGATCACGGTCGAAAAATAGCGGGTGGTTATGGTTATACGCTA 
               
               
                   
                 CATATATGTGATCTTTTGCCTAAGAGCCGAGGCAGAATTGGCCTAAAAAGCGCCAATCCA 
               
               
                   
                 TTACAGCCGCCTTTAATTGACCCGAACTATCTTAGCGATCATGAAGATATTAAAACCATG 
               
               
                   
                 ATTGCGGGTATTAAGATAGGGCGCGCTATTTTGCAGGCCCCATCGATGGCGAAGCATTTT 
               
               
                   
                 AAGCATGAAGTAGTACCGGGCCAGGCTGTTAAAACTGATGATGAAATAATCGAAGATATT 
               
               
                   
                 CGTAGGCGAGCTGAGACTATATACCATCCGGTAGGTACTTGTAGGATGGGTAAAGATCCA 
               
               
                   
                 GCGTCAGTTGTTGATCCGTGCCTGAAGATCCGTGGGTTGGCAAATATTAGAGTCGTTGAT 
               
               
                   
                 GCGTCAATTATGCCGCACTTGGTCGCGGGTAACACAAACGCTCCAACTATTATGATTGCA 
               
               
                   
                 GAAAATGCGGCAGAAATAATTATGCGGAATCTTGATGTGGAAGCATTAGAGGCTAGCGCT 
               
               
                   
                 GAGTTTGCTCGCGAGGGTGCAGAGCTAGAGTTGGCA 
               
               
                   
               
               
                 3 
                 ATGCAGAAACAGCGTACCACCTCTCAGTGGCGTGAACTCGATGCGGCGCATCATCTCCAT 
               
               
                   
                 CCGTTTACCGATACCGCGAGCCTCAATCAGGCGGGTGCGCGTGTGATGACCCGTGGCGAA 
               
               
                   
                 GGCGTGTATCTCTGGGATAGCGAAGGCAACAAAATTATTGATGGCATGGCGGGCCTCTGG 
               
               
                   
                 TGCGTGAACGTGGGCTATGGCCGTAAAGATTTTGCGGAAGCGGCGCGTCGTCAGATGGAA 
               
               
                   
                 GAACTCCCGTTTTATAACACCTTCTTTAAAACCACCCATCCGGCGGTGGTGGAACTCAGC 
               
               
                   
                 AGCCTCCTCGCCGAAGTTACCCCGGCAGGTTTTGATCGTGTGTTTTATACCAACAGCGGC 
               
               
                   
                 AGCGAAAGCGTGGATACCATGATTCGTATGGTGCGTCGTTATTGGGATGTGCAGGGCAAA 
               
               
                   
                 CCGGAAAAAAAAACCCTCATTGGCCGTTGGAACGGCTATCACGGCAGCACCATTGGCGGT 
               
               
                   
                 GCGAGCCTCGGCGGCATGAAATATATGCATGAACAGGGCGATCTCCCGATTCCGGGCATG 
               
               
                   
                 GCGCATATTGAACAGCCGTGGTGGTATAAACATGGCAAAGATATGACCCCGGATGAATTT 
               
               
                   
                 GGCGTGGTTGCGGCGCGTTGGCTCGAAGAAAAAATTCTCGAAATCGGCGCGGATAAAGTG 
               
               
                   
                 GCGGCGTTTGTGGGCGAACCGATTCAGGGTGCGGGCGGTGTGATTGTTCCGCCGGCAACC 
               
               
                   
                 TATTGGCCGGAAATTGAACGTATTTGCCGCAAATATGATGTGCTCCTCGTTGCGGATGAA 
               
               
                   
                 GTGATTTGCGGCTTTGGCCGTACCGGCGAATGGTTTGGCCATCAGCATTTTGGCTTTCAG 
               
               
                   
                 CCGGACCTCTTTACCGCGGCGAAAGGCCTCAGCAGCGGCTATCTCCCGATTGGCGCGGTG 
               
               
                   
                 TTTGTGGGCAAACGTGTTGCGGAAGGTCTCATTGCGGGCGGTGATTTTAACCATGGCTTT 
               
               
                   
                 ACCTATAGCGGCCATCCGGTGTGTGCGGCGGTGGCGCATGCGAATGTTGCGGCGCTCCGT 
               
               
                   
                 GATGAAGGCATTGTGCAGCGTGTGAAAGATGATATTGGCCCGTATATGCAGAAACGTTGG 
               
               
                   
                 CGTGAAACCTTTAGCCGTTTTGAACATGTGGATGATGTGCGTGGCGTGGGCATGGTGCAG 
               
               
                   
                 GCGTTTACCCTCGTGAAAAACAAAGCGAAACGTGAACTCTTTCCGGATTTTGGCGAAATT 
               
               
                   
                 GGCACCCTCTGCCGCGATATTTTTTTTCGCAACAACCTCATTATGCGTGCGTGCGGCGAT 
               
               
                   
                 CACATTGTGTCTGCACCGCCGCTCGTTATGACCCGTGCGGAAGTGGATGAAATGCTCGCC 
               
               
                   
                 GTGGCGGAACGTTGCCTCGAAGAATTTGAACAGACCCTCAAAGCGCGTGGCCTCGCCTAA 
               
               
                   
               
               
                 4 
                 ATGGCAATCGTTGTTGTTGGCGCTGGTACAGCTGGAGTAAATGCTGCGTTCTGGCTTCGT 
               
               
                   
                 CAATATGGTTATAAAGGGGAAATTAGGATTTTTAGCAGGGAGTCTGTGGCGCCTTATCAG 
               
               
                   
                 CGGCCTCCTCTATCCAAGGCTTTTCTGACAAGTGAGATTGCAGAATCCGCAGTGCCATTA 
               
               
                   
                 AAGCCAGAAGGTTTTTATACGAATAACAATATTACCATTTCGTTAAATACACCGATTGTA 
               
               
                   
                 TCAATCGACGTGGGGCGTAAGATAGTTTCTTCTAAAGATGGAAAAGAATACGCGTATGAA 
               
               
                   
                 AAATTGATTCTTGCAACACCTGCTAGCGCACGTAGGTTAACCTGCGAGGGGTCTGAACTG 
               
               
                   
                 TCTGGGGTCTGCTATTTACGCAGTATGGAAGACGCCAAAAATTTACGTAGGAAACTTGTG 
               
               
                   
                 GAGAGTGCGTCTGTTGTTGTGTTGGGCGGCGGAGTAATCGGGCTTGAAGTCGCCTCAGCT 
               
               
                   
                 GCGGTGGGCTTAGGGAAGAGGGTCACAGTGATAGAAGCCACCCCGCGTGTAATGGCGCGC 
               
               
                   
                 GTGGTTACGCCGGCAGCAGCAAACTTAGTCAGAGCCCGCCTGGAGGCTGAAGGAATTGAG 
               
               
                   
                 TTCAAGCTGAATGCGAAATTAACGTCTATAAAGGGCAGGAATGGCCATGTTGAACAATGC 
               
               
                   
                 GTACTTGAAAGTGGAGAAGAAATTCAGGCGGATCTGATTGTAGTTGGAATCGGTGCTATC 
               
               
                   
                 CCAGAGCTAGAGCTGGCAACTGAGGCGGCCCTTGAAGTGAGTAATGGTGTTGTGGTCGAT 
               
               
                   
                 GATCAGATGTGTACATCGGATACAAGTATATATGCAATCGGCGACTGCGCAATGGCTAGA 
               
               
                   
                 AATCCTTTTTGGGGAACGATGGTACGTTTAGAGACAATTCATAATGCGGTTACACACGCT 
               
               
                   
                 CAAATTGTCGCAAGTAGCATCTGTGGCACATCAACACCAGCACCAACCCCACCACGGTTC 
               
               
                   
                 TGGTCTGATCTTAAAGGGATGGCGCTGCAAGGACTTGGTGCTCTAAAGGACTACGATAAA 
               
               
                   
                 CTCGTTGTTGCAATTAATAACGAAACTCTTGAACTAGAAGTCCTTGCGTACAAGCAGGAG 
               
               
                   
                 CGACTGATTGCAACTGAGACAATAAATTTGCCTAAACGTCAAGGTGCGCTTGCAGGGAGT 
               
               
                   
                 ATAAAATTACCTGATTAG 
               
               
                   
               
               
                 9 
                 ATGGCTAGCTATAAATGCCCGGATTGTAATTATGTTTATGATGAGAGTGCGGGTAATGTG 
               
               
                   
                 CATGAGGGGTTTTCTCCAGGTACGCCTTGGCACCTTATTCCTGAGGATTGGTGCTGCCCC 
               
               
                   
                 GATTGCGCCGTTCGAGACAAGCTTGACTTCATGTTAATTGAGAGCGGCGTAGGTGAAAAG 
               
               
                   
                 GGCGTCACCTCAACCCATACTTCGCCAAATTTATCCGAGGTTAGTGGCACAAGTTTAACT 
               
               
                   
                 GCTGAAGCAGTGGTTGCGCCGACAAGCTTAGAGAAATTGCCTAGTGCCGACGTTAAAGGC 
               
               
                   
                 CAAGATCTATATAAAACTCAACCTCCAAGGTCTGATGCCCAAGGCGGGAAAGCATACTTG 
               
               
                   
                 AAGTGGATATGTATTACTTGTGGCCATATATATGATGAGGCGTTGGGCGATGAGGCCGAG 
               
               
                   
                 GGTTTTACTCCAGGTACTCGCTTTGAGGATATTCCTGATGACTGGTGCTGTCCGGATTGC 
               
               
                   
                 GGGGCTACGAAAGAAGACTATGTGCTCTACGAGGAAAAG 
               
               
                   
               
            
           
         
       
     
     Enzymes that are encoded by nucleic acids that have 90%, 95%, 99% and in particular 100% identity to the sequences according to SEQ ID NOs: 1, 2 and 3, are suitable in the method of the present invention. The “nucleotide identity” relative to SEQ ID NOs:1-3 is determined using known methods. In general, special computer programs with algorithms are used, taking into account special requirements. Methods that may be used for determination of identity first produce the greatest agreement between the sequences to be compared. Computer programs for determination of identity comprise, but are not restricted to, the GCG software package, including GAP (Deveroy, J. et al., 1984), and BLASTP, BLASTN and FASTA (Altschul, S. et al., 1990). The BLAST program can be obtained from the National Center for Biotechnology Information (NCBI) and from other sources (BLAST Manual, Altschul S. et al., 1990). 
     The well-known Smith-Waterman algorithm can also be used for determining nucleotide identity. 
     Parameters for nucleotide comparison may comprise the following:
         Algorithm Needleman and Wunsch, 1970,   Comparison matrix
           Matches=+10   Mismatches=0   Gap penalty=50   Gap length penalty=3   
               

     The GAP program is also suitable for use with the parameters given above. These parameters are usually the default parameters in the nucleotide sequence comparison. 
     Moreover, enzymes from the subgroup of the β-Ala:pyruvate transaminases are suitable. These include but are not limited to for example transaminases from  Pseudomonas putida  W619 (gi: 119860707, gi: 119855857, gi: 119856278), from  Pseudomonas putida  KT2440 (gi: 24984391), from  Pseudomonas aeruginosa  PA01 (gi 15595330, gi: 15600506, gi 15595418, gi 9951072);  Streptomyces coelicolor  A3(2) (gi: 3319731),  Streptomyces avermitilis  MA 4680 (gi: 29831094, gi: 29829154) and  Chromobacterium violaceum  ATCC 12472 (gi 34102747). Throughout this application, any data base code, unless specified to the contrary, refers to a sequence available from the NCBI data bases, more specifically the version online on 20 Feb. 2014, and comprises, if such sequence is a nucleotide sequence, the polypeptide sequence obtained by translating the former. 
     The method according to any aspect of the present invention may further comprise a step of converting the aminohexanoic acid ester to aminohexanoic acid. In particular, ω-aminohexanoic acid esters to the corresponding ω-aminohexanoic acids. The recombinant cell according to the method of the present invention may be capable of increased activity of an enzyme which catalyses the conversion of ω-aminohexanoic acid esters to the corresponding ω-aminohexanoic acids, the enzyme may be an esterase, which may be secreted by the cell. Secretion of the esterase by the cell has the advantage that the ester bond is only cleaved outside of the cell. Since the membrane permeability of the ω-aminohexanoic acid ester is better compared to the ω-aminohexanoic acid, the ω-aminohexanoic acid ester leaves the cell and enters the nutrient medium surrounding the cell. The esterases found outside of the cell will then be more efficient in metabolising the conversion of ω-aminohexanoic acid ester to ω-aminohexanoic acid. 
     In particular, the esterase used may be a lipase. In one example, a suitable lipase may be the lipase LipA from  Pseudomonas fluorescens  HU380 (ACC Code Q76D26, Kojima and Shimizu, 2003). In order to ensure that the esterases are secreted out of the cell, the esterases may be provided, in a manner known by a skilled person, with corresponding signal sequences, which establish secretion. If for example the lipase LipA from  Pseudomonas fluorescens  HU380 is overexpressed in  E. coli , it can be provided advantageously with signal sequences from EstA, an esterase that occurs naturally on the cell surface of  Pseudomonas aeruginosa  (Becker et al., 2005). Other suitable enzymes are lipases from  C. antarctica, M. miehei  and  P. cepacia  (Vaysse et al., 2002). 
     Alternatively, the secreted ω-aminohexanoic acid ester can also be cleaved conventionally, to obtain the ω-aminohexanoic acid, for example by saponification, i.e. hydrolysis of the ω-aminohexanoic acid ester by the aqueous solution of a hydroxide, for example sodium hydroxide. 
     In one example, the ω-aminohexanoic acid may be converted to lactams. Lactams are cyclic amides that may form the basis for formation of polyamides. In particular, ring opening polymerisation of lactams may lead to the formation of nylon. More in particular, 6-hexanolactam may be polymerised to form nylon-6. 
     In the production of ω-aminohexanoic acids, ω-aminohexanoic acid esters or of lactams derived from ω-aminohexanoic acids, the following process steps are carried out:
         I) contacting the recombinant cell according to any aspect of the present invention with a culture medium containing the C 1 -C 4  hexanoate or with a culture medium contiguous with an organic phase containing the C 1 -C 4  hexanoate in conditions that enable the cell to form ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids, from the C 1 -C 4  hexanoate; and/or   II) isolation of the resultant ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids.       

     The genetically modified cells used according to the method of the invention can be brought into contact with a nutrient medium, and therefore cultivated continuously or discontinuously in a batch process or in a fed-batch process or in a repeated-fed-batch process, for the purpose of producing ω-aminohexanoic acids, or lactams derived from ω-aminohexanoic acids. A semi-continuous process is also conceivable, as described in GB1009370A. Known culture methods are described in Chmiel&#39;s textbook, 1991 or in the textbook by Storhas 1994. 
     The culture medium to be used must be suitable for the requirements of the particular strains. Descriptions of culture media for various microorganisms are given in “ Manual of Methods for General Bacteriology”.    
     Organic nitrogen-containing compounds such as peptones, yeast extract, meat extract, malt extract, corn-steep liquor, soybean flour and urea or inorganic compounds such as ammonium sulphate, ammonium chloride, ammonium phosphate, ammonium carbonate and ammonium nitrate can be used as the nitrogen source. The nitrogen sources can be used separately or as a mixture. 
     In one example, according to any aspect of the present invention at least during the phase of formation of ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids, the culture medium used in step I) contains amino group donors, such as ammonia or ammonium ions or even amino acids, though in particular alanine or aspartate, which function as amine donors in the transaminase-catalysed conversion of the ω-oxohexanoic acids and/or the ω-oxohexanoic acid esters to the corresponding ω-aminohexanoic acids and/or ω-aminohexanoic acid esters. 
     Phosphoric acid, potassium dihydrogen phosphate or dipotassium hydrogen phosphate or the corresponding sodium-containing salts can be used as the source of phosphorus. The culture medium may in addition contain salts of metals, for example magnesium sulphate and/or iron sulphate, which are required for growth. Essential growth substances such as amino acids and/or vitamins may also be used in addition to the substances mentioned above. Suitable precursors can also be added to the culture medium. The above substances can be added to the culture in the form of a single preparation, or they can be supplied in a suitable manner during cultivation. 
     Basic compounds such as sodium hydroxide, potassium hydroxide, ammonia, ammonia water and/or acid compounds such as phosphoric acid or sulphuric acid may be used in a suitable manner for controlling the pH of the culture. Antifoaming agents, e.g. fatty acid polyglycol esters, may be used for controlling foaming. Plasmid stability may be maintained with use of suitable antibiotics in the culture medium. Aerobic conditions may be maintained with use of oxygen or oxygen-containing gas mixtures, e.g. air, may be fed into the culture medium. The temperature of the culture may be in the range from 20° C. to 45° C. or 25° C. to 40° C. 
     In one example, in the method according to the invention for the production of ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids, a recombinant cell, derived from an  E. coli  is used in a mineral salt medium supplemented with ampicillin, chloramphenicol and kanamycin according to Riesenberg et al., 1990. 
     In one example, in the method according to the invention, the cells are first cultivated, for the purpose of biomass production in a nutrient medium that does not contain C 1 -C 4  hexanoate. It is only after a certain biomass has been obtained that the C 1 -C 4  hexanoate is added to the nutrient medium and/or the cells are brought into contact with a new nutrient medium containing the C 1 -C 4  hexanoate. In this regard, the amount of C 1 -C 4  hexanoate present during the formation of ω-aminocarboxylic acids, ω-amino hexanoic acid esters and/or lactams derived from ω-amino hexanoic acids may be in the range from 1 to 200 g/l, especially in the range from 20 to 200 g/l. 
     According to one example of the present invention, the method according to the invention is carried out in a two phase system, containing an aqueous phase, and an organic phase. The formation of the ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids by the recombinant cells in step I) takes place in the aqueous phase. The resultant ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids accumulate in the organic phase. In this way it is possible for the resultant ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or the lactams derived from (ω-aminohexanoic acids to be extracted in situ. 
     As organic phase, it is possible to use alkanes of medium chain length and those with a log P value of more than 4 (little foam formation), or physically similar aromatics or aromatic esters. In step II) of the method according to the invention, the resultant ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or the lactams derived from the ω-aminohexanoic acids are optionally isolated, and it may for this isolation take place in a two-stage purification process, comprising
         a) an extraction step, in which the ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids are extracted from the culture medium, and   b) a fine purification step, in which the extract obtained in step a) is purified further by a distillation process or selective crystallization, obtaining an ω-aminohexanoic acid phase, an ω-aminohexanoic acid ester phase and/or a lactam phase with a purity of at least 99.8%.       

     The extraction in step a) can in particular be designed as sω-called “in situ” extraction, in which steps I) and II) of the method according to the invention for the production of ω-aminohexanoic acids, ω-aminohexanoic acid esters and/or lactams derived from ω-aminohexanoic acids are carried out simultaneously. 
     The fine purification in step II) can for example take place by distillation or crystallization. 
     In one example, the aminohexanoic ester may be converted to aminohexanoic acid using a chemically analogous procedure known in the art. 
     A further enzyme may catalyse the conversion of ω-aminocarboxylic acids to the corresponding lactams, and it can also be advantageous here if this enzyme is secreted by the cell. In this way it can be possible for the ω-aminocarboxylic acids formed directly by the cell or the ω-aminocarboxylic acid that is only formed after extracellular cleavage of ω-aminocarboxylic acid esters to be converted to the corresponding lactam, thus optionally facilitating purification of the target product. 
     In another example, the aminohexanoic acid is catalysed directly to form nylon. Nylon is the term commonly used to describe aliphatic polyamides. Common aliphatic polyamides such as nylon 6, nylon 6,6 and nylon 6,10 exhibit high mechanical strength, toughness, and chemical resistance, and can be drawn to form high-strength fibres. The nylon may be selected from the group consisting of nylon-6,6, nylon-6, nylon-6,9, nylon-6,10, and nylon-6,12. In particular, the nylon may be nylon-6,6, nylon-6, nylon-6,9, nylon-6,10 or nylon-6,12. Even more in particular, the nylon may be nylon-6. In one example there may be more than one type of nylon formed in the reaction. 
     Nylon may be produced from the aminohexanoic acid and/or aminohexanoic acid ester using any method known in the art. In one example, the nylon may be produced from the lactam derived from the ω-aminohexanoic acid. 
     The production of the polyamides from lactams can be carried out by well-known methods, as described for example in DE1495198, DE2558480, EP0129196 or also in “ Polymerization Processes ”, 1977. 
     In another example, the nylon 6 may be produced directly by polycondensation of ω-aminohexanoic acid and/or lactams derived therefrom. 
     In particular, the nylon may be based, up to at least 10 wt. %, at least 25 wt. %, at least 50 wt. % or up to at least 75 wt. %, on ω-aminohexanoic acid, ω-aminohexanoic acid ester and/or lactam derived from the ω-aminohexanoic acid. 
     According to another aspect of the present invention, there is provided an aminohexanoic acid and/or aminohexanoic acid ester obtained by the method of the present invention. There may also be provided a lactam derived from the aminohexanoic acid produced according to the method of the present invention. 
     According to one aspect of the present invention, there is provided a method for the production of nylon based on aminohexanoic acid and/or aminohexanoic acid ester comprising:
         producing an aminohexanoic acid and/or aminohexanoic acid ester by the method according to any aspect of the present invention; and   polymerizing the aminohexanoic acid and/or aminohexanoic acid ester to obtain a nylon.       

     According to yet another aspect there is provided a nylon obtained by the method according to any aspect of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows expression vector pBT10 (A) for the alkane monooxygenase (AlkBGT) (Schrewe et al., 2011) and PJ10 (B) for the alcohol dehydrogenase AlkJ 
         FIG. 2  is a graph showing the whole cell reaction (hydroxylation) of hexanoic acid to methyl hexanoate with  E. coli  JM101 (pBT10) by measuring the total concentration of methyl hexanoate, 6-hydroxy methylhexanoate (6 hydroxy hexanoic acid methylester) and oxomethyl hexanoate (6-oxo hexanoic acid methylester). Biomass concentration: 0.68±0.02 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 3  is a graph showing the measurement of specific activity in the whole cell reaction where step 1 is the measurement of hydroxylation of hexanoic acid to methyl hexanoate with  E. coli  JM101 (pBT10) and step 2 is the measurement of the alcohol oxidation step. Biomass concentration: 0.68±0.02 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 4  is a graph showing the whole cell reaction of 6-hydroxy methylhexanoate to oxomethyl hexanoate with  E. coli  JM101 (pBT10) by measuring the total concentration of 6-hydroxy methylhexanoate (6 hydroxy hexanoic acid methylester) and oxomethyl hexanoate (6-oxo hexanoic acid methylester). Biomass concentration: 0.86 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 5  is a graph showing the measurement of specific activity in the whole cell reaction of the alcohol oxidation step (6-hydroxy methylhexanoate (6 hydroxy hexanoic acid methylester) and oxomethyl hexanoate (6-oxo hexanoic acid methylester). Biomass concentration: 0.86 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 6  is a graph showing the whole cell reaction of 6-hydroxy methylhexanoate to oxomethyl hexanoate with  E. coli  JM101 (pJ10) by measuring the total concentration of 6-hydroxy methylhexanoate (6 hydroxy hexanoic acid methylester) and oxomethyl hexanoate (6-oxo hexanoic acid methylester). Biomass concentration: 0.91 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 7  is a graph showing the measurement of specific activity in the whole cell reaction of hydroxylation of 6-hydroxy methylhexanoate to oxomethyl hexanoate with  E. coli  JM101 (pJ10). Biomass concentration: 0.91 g CDW  L −1  in KPi-buffer (pH 7.4) containing 1% (w/v) glucose. Data was each measured in duplicates from two biological replicates. 
         FIG. 8  shows the starting plasmid pGEc47, which was used as template for the amplification of alkBGTS. 
         FIG. 9  shows the primers used and the resultant PCR products alkBFG and alkT. The primer sequences shown in the figure are as follows: alkBFG forward is SEQ ID NO:5; alkBFG reverse is SEQ ID NO:6; alkT forward is SEQ ID NO:7 and alkT reverse is SEQ ID NO:8. 
     
    
    
     EXAMPLES 
     The foregoing describes preferred embodiments, which, as will be understood by those skilled in the art, may be subject to variations or modifications in design, construction or operation without departing from the scope of the claims. These variations, for instance, are intended to be covered by the scope of the claims. 
     Example 1 
     Production of Ethanol and Acetate from Synthesis Gas 
     For the biotransformation of synthesis gas (66% H 2 , 33% CO 2 ) to ethanol and acetate, the bacterium  Clostridium ljungdahlii  was used. All cultivation steps were carried out under anaerobic conditions in pressure-resistant glass bottles that can be closed airtight with a butyl rubber stopper. 
     For the cell culture of  C. ljungdahlii  5 mL cryoculture was grown anaerobically in 50 ml of ATCC1754 medium (ATCC1754 medium: pH 6.0, 20 g/L MES, 1 g/L yeast extract, 0.8 g/L NaCl, 1 g/L NH 4 Cl, 0.1 g/L KCl, 0.1 g/L KH 2 PO 4 , 0.2 g/L MgSO 4 .7H 2 O, 0.02 g/L CaCl 2 x2H 2 O, 20 mg/L nitrilotriacetic acid, 10 mg/L MnSO 4 xH 2 O, 8 mg/L (NH 4 ) 2 Fe(SO 4 ) 2 x6H 2 O, 2 mg/L CoCl 2 x6H 2 O, 2 mg/L ZnSO 4 .7H 2 O, 0.2 mg/L CuCl 2 x2H 2 O, 0.2 mg/L Na 2 MoO 4 x2H 2 O, 0.2 mg/L NiCl 2 x6H 2 O, 0.2 mg/L Na 2 SeO 4 , 0.2 mg/L Na 2 WO 4 x2H 2 O, 20 g/L d-biotin; 20 μg/L folic acid, 100 μg/L pyridoxine HCl, 50 g/L thiamine-HClxH 2 O, 50 g/L riboflavin, 50 g/L nicotinic acid, 50 g/L calcium pantothenate, 1 g/L vitamin B12, 50 g/L p-aminobenzoate, 50 μg/L lipoic acid, about 67.5 mg/L NaOH, 400 mg/L L-cysteine hydrochloride, 400 mg/L Na 2 Sx9 H 2 O, 5 g/L fructose). From this culture, 10 ml was taken and inoculated in 100 ml of ATCC1754 medium to start the growth culture. This growth culture was incubated at 35° C. for 3 days. 
     For the production phase, the cells were harvested from the growth culture and washed with production medium. Subsequently, the cell pellet was resuspended in 75 ml of production medium (DM4 Medium: pH 5.8; 15 mg/l FeCl 2 x4H 2 O, 2 g/l (NH 4 )H 2 PO 4 , 0.2 g/l NaCl, 0.15 g/l KCl, 0.5 mg/l Resazurin, 3 mg/l H 3 BO 3 , 2 mg/l CoCl 2 x6H 2 O, 1 mg/l ZnSO 4 x7H 2 O, 300 μg/l Na 2 MoO 4 x2H 2 O, 300 μg/l MnSO 4 xH 2 O, 200 μg/l NiCl 2 x6H 2 O, 100 μg/L CuCl 2 x2H 2 O, 100 μg/l Na 2 SeO 3 , 106 μg/l d-Biotin, 5 μg/l Folic acid, 2.5 μg/l Pyridoxin-HCl, 266 μg/l Thiamin-HCl, 12.5 μg/l Riboflavin; 12.5 μg/l Nicotinic acid, 413 μg/l Ca-pantothenate, 12.5 μg/l Vitamin B 12 , 12.5 μg/l p-aminobenzoate, 15.0 μg/l lipoic acid, 0.5 g/l MgCl 2 x7H 2 O, 0.2 g/l CaCl 2 x2H 2 O in flameproof, sterile glass bottles (volume 250 ml) and the production phase of  C. ljungdahlii  started. The production culture was capped with a butyl rubber stopper with synthesis gas (66% H 2 , 33% CO 2 , 1.8 bar) and left for 113.75 h and incubated at 35° C. and shaken at 100 rpm. During the cultivation, the gas phase was changed daily and samples were taken daily to determine the optical density and different analytes produced by NMR. The results showed that the amount of acetate produced increased from 0.02 g/l to 1.2 g/l and the amount of ethanol produced increased from 0.01 g/l to 0.1 g/l. Hexanoic acid and butyric acid could not be detected. 
     Example 2 
     Production of Butyric and Hexanoic Acid from Synthesis Gas 
     For the biotransformation of synthesis gas to butyric acid and hexanoic acid, a ω-culture of  Clostridium ljungdahlii  and  Clostridium kluyveri  was used in the production phase. The bacterium  Clostridium ljungdahlii  converted the H 2  and CO 2  from the ambient atmosphere to acetate and ethanol. These products were taken up by from the aqueous phase and converted into butyric acid and hexanoic acid by the  Clostridium kluyveri.    
     All cultivation steps were carried out under anaerobic conditions in pressure-resistant glass bottles that can be closed airtight with a butyl rubber stopper. 
     For the cell culture of  C. ljungdahlii  10 mL cryoculture was grown anaerobically in 100 ml of ATCC1754 medium (ATCC1754 medium: pH 6.0, 20 g/L MES, 1 g/L yeast extract, 0.8 g/L NaCl, 1 g/L NH 4 Cl, 0.1 g/L KCl, 0.1 g/L KH 2 PO 4 , 0.2 g/L MgSO 4 .7H 2 O, 0.02 g/L CaCl 2 x2H 2 O, 20 mg/L nitrilotriacetic acid, 10 mg/L MnSO 4 xH 2 O, 8 mg/L (NH 4 ) 2 Fe(SO 4 ) 2 x6H 2 O, 2 mg/L CoCl 2 x6H 2 O, 2 mg/L ZnSO 4 .7H 2 O, 0.2 mg/L CuCl 2 x2H 2 O, 0.2 mg/L Na 2 MoO 4 x2H 2 O, 0.2 mg/L NiCl 2 x6H 2 O, 0.2 mg/L Na 2 SeO 4 , 0.2 mg/L Na 2 WO 4 x2H 2 O, 20 g/L d-biotin; 20 μg/L folic acid, 100 μg/L pyridoxine HCl, 50 g/L thiamine-HClxH 2 O, 50 g/L riboflavin, 50 g/L nicotinic acid, 50 g/L calcium pantothenate, 1 g/L vitamin B12, 50 g/L p-aminobenzoate, 50 μg/L lipoic acid, about 67.5 mg/L NaOH, 400 mg/L L-cysteine hydrochloride, 400 mg/L Na 2 Sx9 H 2 O, 5 g/L fructose). This growing culture was incubated at 35° C. for 2 days. 
     For the cell culture of  Clostridium kluyveri,  10 mL of a continuous culture of  Clostridium kluyveri , was grown in 100 mL of DMSZ52 medium (DSMZ52 medium: pH=6.98, 10 g/L CH 3 COOK, 0.31 g/L K 2 HPO 4 , 0.23 g/L KH 2 PO 4 , 0.25 g/l NH 4 Cl, 0.20 g/l MgSO 4 x7 H 2 O, 1 g/L yeast extract, 0.50 mg/L resazurin, 10 μl/l HCl (25%, 7.7 M), 1.5 mg/L FeCl 2 x4H 2 O, 70 g/L ZnCl 2 x7H 2 O, 100 g/L MnCl 2 x4H 2 O, 6 g/L H 3 BO 3 , 190 μg/L COCl 2 x6H 2 O, 2 g/L CuCl 2 x6H 2 O, 24 g/L NiCl 2 x6H 2 O, 36 g/L Na 2 MO 4 x2H 2 O, 0.5 mg/L NaOH, 3 g/L Na 2 SeO 3 x5H 2 O, 4 μg/L Na 2 WO 4 x2H 2 O, 100 g/L vitamin B12, 80 g/L p-aminobenzoic acid, 20 g/L D(+) Biotin, 200 μg/L nicotinic acid, 100 g/L D-Ca-pantothenate, 300 μg/L pyridoxine hydrochloride, 200 μl/l thiamine —HClx2H 2 O, 20 mL/L ethanol, 2.5 g/L NaHCO 3 , 0.25 g/L cysteine-HClxH 2 O, 0.25 g/L Na 2 Sx9H 2 O). This growing culture was incubated at 35° C. for 2 days. 
     For the production phase, the cells were harvested from both growth cultures separately and washed with production medium. Subsequently, the cell pellets were each resuspended in 35 ml of production medium (PETC mod. Medium: pH 6.0; 10 g/l MES, 2.4 g/l of NaCl, 3 g/l NH 4 Cl, 0.3 g/l KCl, 0.3 g/l KH 2 PO 4 , 0.6 g/l MgSO 4 .7H 2 O, 0.12 g/l CaCl 2 x2H 2 O, 20 mg/l nitrilotriacetic acid, 10 mg/l MnSO 4 xH 2 O, 8 mg/l (NH 4 ) 2 Fe(SO 4 ) 2 x6H 2 O, 2 mg/l CoCl 2 x6H 2 O, 2 mg/l ZnSO 4 .7H 2 O, 0.2 mg/l CuCl 2 x2H 2 O, 0.2 mg/l Na 2 MoO 4 x2H 2 O, 0.2 mg/l NiCl 2 x6H 2 O, 0.2 mg/l Na 2 SeO 4 , 0.2 mg/l Na 2 WO 4 x2H 2 O, 2 g/l d- biotin, 2 g/l folic acid, 10 g/l pyridoxine HCl, 5 g/l thiamine-HClxH 2 O, 5 g/l of riboflavin, 5 g/l nicotinic acid, 5 g/l of Ca-pantothenate, 5 μg/L vitamin B12, 5 g/l p-aminobenzoate, 5 μg/l lipoic acid, 10 g/l MESNA, approximately 67.5 mg/l NaOH, 300 mg/l cysteine-HClxH 2 O, 300 mg/l Na 2 Sx9H 2 O) in flameproof, sterile glass bottles (volume 250 ml) and the co-production of  C. ljungdahlii  and  C. kluyveri  started. The production culture was capped with a butyl rubber stopper with synthesis gas (66% H 2 , 33% fully  13 C-labeled CO 2 , 1.8 bar) and left for 191 h and incubated at 35° C. and shaken at 100 rpm. During the cultivation, the gas phase was changed daily and samples were taken daily to determine the optical density and different analytes produced by NMR. 
     The amount of products is determined using semi-quantitative  1 H-NMR spectroscopy of a sterile-filtered supernatant from this mixed production. The samples were in accordance with phosphate buffer diluted (in D 2 O stated) and measured with water suppression. Measurements were carried out with and without suppression of  13 C coupling. As an internal quantification standard, sodium trimethylsilylpropionate (TSP) was used. 
     The results showed that the amount of acetate produced increased from 0.05 g/l to 1.7 g/l (93 mol % of the total acetate produced was  13 C marked) and the amount of ethanol produced increased from 0.05 g/l to 0.12 g/l (92 mol % of the total ethanol produced was  13 C marked). Also, the concentration of hexanoic acid was increased from 0.02 g/l to 0.13 g/l (63 mol % of the total hexanoic acid produced was  13 C marked) and butyric acid was increased from 0.01 g/l to 0.07 g/l (63 mol % of the total butyric acid produced was  13 C marked). This confirmed that a large percentage of the hexanoic acid and butyric acid produced derived from the C source of the synthesis gas. 
     Example 3 
     Production of Hexanoic Acid and Butyric Acid from Ethanol and Acetate 
     For the biotransformation of ethanol and acetate to hexanoic acid and butyric acid the bacterium  Clostridium kluyveri  was used. All cultivation steps were carried out under anaerobic conditions in pressure-resistant glass bottles that can be closed airtight with a butyl rubber stopper. 
     A cyroculture of  Clostridium  in 5 ml of DMSZ52 medium (DSMZ52 medium: pH=6.98, 10 g/L CH 3 COOK, 0.31 g/L K 2 HPO 4 , 0.23 g/L KH 2 PO 4 , 0.25 g/l NH 4 Cl, 0.20 g/l MgSO 4 x7 H 2 O, 1 g/L yeast extract, 0.50 mg/L resazurin, 10 μl/l HCl (25%, 7.7 M), 1.5 mg/L FeCl 2 x4H 2 O, 70 μg/L ZnCl 2 x7H 2 O, 100 μg/L MnCl 2 x4H 2 O, 6 μg/L H 3 BO 3 , 190 μg/L COCl 2 x6H 2 O, 2 μg/L CuCl 2 x6H 2 O, 24 μg/L NiCl 2 x6H 2 O, 36 μg/L Na 2 MO 4 x2H 2 O, 0.5 mg/L NaOH, 3 μg/L Na 2 SeO 3 x5H 2 O, 4 μg/L Na 2 WO 4 x2H 2 O, 100 g/L vitamin B12, 80 g/L p-aminobenzoic acid, 20 g/L D(+) Biotin, 200 μg/L nicotinic acid, 100 μg/L D-Ca-pantothenate, 300 μg/L pyridoxine hydrochloride, 200 μl/L thiamine —HClx2H 2 O, 20 mL/L ethanol, 2.5 g/L NaHCO 3 , 0.25 g/L cysteine-HClxH 2 O, 0.25 g/L Na 2 Sx9H 2 O) was placed in a 250 ml bottle and 50 ml of DSMZ52 medium added. This growing culture was incubated at 35° C. for 3 days. Then 100 ml of DSMZ52 medium was inoculated with 10 ml of this culture to produce a preparatory culture. This preparatory culture was incubated at 35° C. for 3 days. For production of a main culture, 200 ml of DSMZ52 medium was inoculated with 5% of the cells from the preparatory culture in 500 ml bottles. The culture was capped with a butyl rubber stopper and incubated for 98 h and incubated at 35° C. At the start and end of the culturing period, samples were taken. These were tested for optical density and the different analytes by NMR. There was a growth of OD 600 ˜0.01 to a maximum of 0.35 to 0.37. The results showed that the amount of acetate decreased from 4.9 g/l to 2.4 g/l and the amount of ethanol decreased from 12.5 g/l to 9.2 g/l. Also, the concentration of hexanoic acid was increased from 0.1 g/l to 6.85 g/l and butyric acid was increased from 0.1 g/l to 2.9 g/l. 
     Example 4 
     The Formation of Hexanoic Acid from Synthesis Gas Using  C. carboxidivorans    
     The wild-type strain  Clostridium carboxidivorans  (Accession No. DSM 15243) were obtained from DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH) and cultivated autotrophically to form hexanoic acid from synthesis gas. All cultivation steps were carried out under anaerobic conditions in pressure-resistant glass bottles that can be closed airtight with a butyl rubber stopper. 
     A complex medium was used to grow the cells. The complex medium was made of: 3 g/l NH 4 Cl, 0.3 g/l KCl, 0.6 g/l MgSO 4 x7H 2 O, 2.4 g/l NaCl, 0.3 g/l KH 2 PO 4 , 120 mg/l CaCl 2 x2 H 2 O, 10 g/l MES, 1 g/l yeast extract, 0.4 g/l L-Cysteine-HCl, 20 mg/l nitrilotriacetic acid, 10 mg/l MnSO 4 xH 2 O, 8 mg/l (NH 4 ) 2 Fe(SO 4 ) 2 x6H 2 O, 2 mg/l CoCl 2 x6H 2 O, 2 mg/l ZnSO 4 x7H 2 O, 0.2 mg/l CuCl 2 x2H 2 O, 0.2 mg/l Na 2 MoO 4 x2H 2 O, 0.2 mg/l NiCl 2 x6H 2 O, 0.2 mg/l Na 2 SeO 4 , 0.2 mg/l Na 2 WO 4 x2H 2 O, 20 μg/l d-Biotin, 20 μg/l folic acid, 100 μg/l Pyridoxin-HCl, 50 μg/l Thiamin-HClxH 2 O, 50 μg/l Riboflavin, 50 μg/l nicotinic acid, 50 μg/l Ca-pantothenate, 50 μg/l Vitamin B 12 , 50 μg/l p-aminobenzoate, 50 μg/l lipoic acid, 100 μg/l MESNA pH 6.0. 
     An autotrophic cultivation was carried out in a 1 L-septum bottle filled with 500 ml of the complex medium and the  Clostridium carboxidivorans  strain. The incubation was performed at 37° C. with a shaking frequency of 100 min −1  in an open water bath shaker (Innova 3100 by New Brunswick Scientific). The gas trapped in the medium was removed by a sparger with a pore size of 10 microns, which was mounted in the center of the reactors. Culturing is carried out with no pH control. The reactors were purged with a premixed gas mixture of composition 67% H 2 , 33% CO 2  at atmospheric pressure with an aeration rate of 3 I/h (0.1 vvm) through the sparger. 
     The reactor started with 5 ml of a cryoculture of  Clostridium carboxidivorans  inoculated in glycerol (10%) that was heterotrophic with fructose in the absence of O 2  in the abovementioned complex medium. The culture was and incubated for 46 h and incubated at 35° C. 
     When obtaining samples, 5 ml of each sample as taken for determination of OD 600 , pH and the product spectrum. The determination of the product concentration was performed by semi-quantitative  1 H-NMR spectroscopy. As an internal quantification standard sodium trimethylsilylpropionate (T(M)SP) was used. 
     The results showed an increase in OD 600  of 0.01 to 0.18 with a decrease in pH from 5.75 to 5.51. Also, the acetate concentration decreased from 7 mg/l to 0.8 g/l, the ethanol concentration increased from 0 g/l to 0.16 g/l and the butyrate concentration increased from 0 to 0.19 g/l. Also, 63 mg/l of hexanoic acid was formed during this period. 
     Example 5 
       E. coli  JM101 (pBT10) as Whole Cell Catalyst for Oxidation of Methyl Hexanoate and/or Hydroxymethyl Hexanoate 
     A recombinant  E. coli  strain JM101 cells which carry the plasmid pBT10 ( FIG. 1A ) expressing the three genes alkane hydroxylase (AlkB), rubredoxin (AlkG) and rubredoxin reductase (AlkT) from  Pseudomonas putida  were produced according to Schrewe et al., 2011 and WO02009077461A1. 
     In summary, the following steps were carried out. 
     Construction of the alkBGT Expression Vectors 
     The construct pBT10 ( FIG. 1A , SEQ ID NO: 1), which contains the three components alkane hydroxylase (AlkB), rubredoxin (AlkG) and rubredoxin reductase (AlkT) from  Pseudomonas putida  that are necessary for the oxidation to the aldehyde, was produced starting from the pCOM systems (Smits et al., 2001). For expression of the three genes, the alkBFG gene sequence was put under the control of the alkB-promoter and the alkT gene under the control of the alkS-promoter (SEQ ID NO:9). 
     Cloning Strategy 
     To simplify the cloning of alkB and alkG, the gene alkF located between them was amplified and cloned together with alkB and alkG. AlkF is of no significance for the reaction that is to be catalysed. 
     PCR amplification of the fragment alkBFG=2524 bp (cf. SEQ ID NO:2 (alkB) and SEQ ID NO:3 (alkG) with Ndel cleavage site upstream of alkB and Sail cleavage site downstream of alkG. The sequences of the primers are provided in Table 2 below. 
     PCR amplification of the fragment alkT (2958 bp) (SEQ ID NO:4 (alkT)) 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Primers used to amplify alkBFG and alkT 
               
            
           
           
               
               
               
            
               
                 SEQ 
                   
                   
               
               
                 ID NO 
                 Sequence 
                 Description 
               
               
                   
               
               
                 5 
                 AAGGGAATTCCATATGCTTG 
                 alkBFG forward 
               
               
                   
                 AGAAACACAGAGTTC 
                   
               
               
                   
               
               
                 6 
                 AAAATTCGCGTCGACAAGCG 
                 alkBFG reverse 
               
               
                   
                 CTGAATGGGTATCGG 
                   
               
               
                   
               
               
                 7 
                 TGAGACAGTGGCTGTTAGAG 
                 alkT forward 
               
               
                   
               
               
                 8 
                 TAATAACCGCTCGAGAACGC 
                 alkT reverse 
               
               
                   
                 TTACCGCCAACACAG 
               
               
                   
               
            
           
         
       
     
     The fragments alkBFG and alkT were amplified by PCR. The plasmid pGEc47 ( FIG. 8 ) (Eggink et al. (1987)) was used as template. 
     The cloning was carried out by means of the subcloning vector pSMART® HCKan (Lucigen Corporation) which was already linearized and provided with blunt ends, and was ligated with the respective blunt-end PCR product ( FIG. 9 ). 
     Next, the alkBFG fragment with the restriction enzymes Ndel and Sail and the alkT fragment with the restriction enzymes Pacl and Xhol were cut out of the subcloning vectors. The fragments were separated in agarose gel (1%), cut out of the gel and isolated using a gel extraction kit. 
     The fragments were ligated one after another into the vector pCOM10 (Smits, T. H. M. et. al., 2001). In the first step alkBFG was inserted in pCOM10 via the cleavage sites Ndel and Sail, and in a second step alkT was then cloned via the cleavage sites Pacl and Xhol. 
     The recombinant plasmid was transformed in  E. coli  DH 5 α. Plasmid-bearing clones were selected on kanamycin-containing LB medium. The isolated plasmid was checked by restriction analysis and sequencing. It is designated pBT10 ( FIG. 1A ). For the biotransformation, the plasmid pBT10 was transformed by heat shock at 42° C. for 2 min in the chemically competent strain  E. coli  JM101. 
     All cell assays were carried out using the following conditions: 
     The  E. coli  strain JM101 cells were grown at 30° C. in M9 medium (composition: 6.8 g/l Na 2 PO 4 .2H 2 O, 2.4 g/l KH 2 PO 4 , 0.4 g/l NaCl, 1.6 g/l NH 4 Cl, 0.5 g/l MgSO 4 .7H 2 O, 1 ml of trace element solution US3, consisting of 36.5 g/l of 37% strength hydrochloric acid, 1.91 g/l MnCl 2 .4H 2 O, 1.87 g/l ZnSO 4 .7H 2 O, 0.84 g/l Na-EDTA.2H 2 O, 0.3 g/l H 3 BO 3 , 0.25 g/l Na 2 MoO 4 .2H 2 O, 4.7 g/l CaCl 2 .2H 2 O, 17.3 g/l FeSO 4 .7H 2 O, 0.15 g/l CuCl 2 .2H 2 O). Inoculation was done when the OD 450 =0.2. The cells were left to grow and when OD 450  reached 0.5, induction of gene expression was carried out with 0.025% (v/v) dicyclopropylketone (DCPK), a potent gratuitous inducer of alkane hydroxylase activity. The cells were incubated for a further 4 hours. The cells were then harvested by centrifugation, the cell pellet was resuspended in 50 mM potassium phosphate buffer (KPi, pH 7.4 containing 1% (w/v) glucose and put in a bioreactor. The growth was stopped with 40 μl of 10% (v/v) perchloric acid which allows for protonation to the resulting acid and thus makes the extraction of the reaction mixture by ether feasible. 
     The reaction mixture was then extracted by diethyl ether and subsequent quantification of the substrate and product concentrations carried out by gas chromatography. Each of the recombinant cells was contacted with methyl hexanoate separately in a resting cell assay and samples taken over a longer period. 
     Resting  E. coli  JM101 (pBT10) catalysed the conversion of methyl hexanoate to hydroxymethyl hexanoate efficiently as shown in  FIGS. 2 and 3 . The AlkBGT-catalysed oxidation of hydroxymethyl hexanoate to oxomethyl hexanoate occurred only to a small extent. 
     As can be seen in Table 3 below, the maximum specific activity for the hydroxylation reaction (first step) was shown to be approximately 90 U g CDW  and for the alcohol oxidation step (second step) was shown to be 6 U g CDW . 
     When hydroxymethyl hexanoate was used as a substrate for  E. coli  JM101 (pBT10), there was a slow and inefficient AlkBGT-catalyzed oxidation of alcohol hydroxymethyl hexanoate to oxomethyl hexanoate. A similar behaviour was observed when hydroxymethyl hexanoate was used as a substrate for  E. coli  JM101 (pBT10) as shown in  FIGS. 4 and 5 . A highest hydroxymethyl hexanoate oxidation rate of 25 U g CDW  was measured and oxomethyl hexanoate accumulation stopped after 15 minutes, although significant amounts of substrate were still present. This showed that AlkBGT is not efficient in oxidation of alcohol hydroxymethyl hexanoate to oxomethyl hexanoate. 
     Example 6 
       E. coli  JM101 (pJ10) as Whole Cell Catalyst for Oxidation of Hydroxymethyl Hexanoate 
     The alkane hydroxylase system alkBGT from  Pseudomonas putida  GPo1 is used for the hydroxylation of hexanoic acid or of methyl hexanoate. The second step to the aldehyde is catalysed by the alcohol dehydrogenase alkJ. 
     A second recombinant  E. coli  strain JM101 cells which carry the plasmid pJ10 expressing the gene encoding for the alcohol dehydrogenase AlkJ from  P. putida  ( FIG. 1  B) were produced. 
     A more efficient hydroxymethyl hexanoate oxidation was achieved by the introduction of the alcohol dehydrogenase AlkJ in  E. coli  JM101. The oxidising ability of  E. coli  JM101 (pJ10) carrying AlkJ was examined in resting cell assays. Hydroxymethyl hexanoate was used as a substrate and the results shown in  FIGS. 6 and 7 . As shown in Table 3 below, the measurement of hydroxymethyl hexanoate oxidation was more than 200 U g CDW . These results showed that AlkJ catalyses the oxidation of alcohols, and is more efficient than AlkBGT in catalysing this reaction. AlkJ is thus an important component in the development of a whole cell catalyst for the production of 6-aminohexanoicmethyl ester via 6-oxoaminohexanoicmethyl ester. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Measurement of maximum specific activity in the production 
               
               
                 of methyl hexanoate and 6-hydroxymethylhexanoate with resting 
               
               
                   E. coli  JM101 (pBT10) and  E. coli  JM101 (pJ10). Biomass 
               
               
                 concentration 0.68-0.91 g CDW  L −1  in KPi-buffer 
               
               
                 (pH 7.4) containing 1% (w/v) glucose 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Step 1 
                 Step 2 
               
               
                 Plasmid 
                 Substrate 
                 [U/g CDW ] 
                 [U/g CDW ] 
               
               
                   
               
               
                 pBT10 
                 Hexanoic acid methylester 
                 90 ± 10 
                  6 ± 2 
               
               
                   
                 6-Hydroxyhexanoicmethylester 
                 — 
                 25 ± 2 
               
               
                 pJ10 
                 6-Hydroxyhexanoicmethylester 
                 — 
                 232 ± 39 
               
               
                   
               
            
           
         
       
     
     For efficient oxidation of the alcohol to the aldehyde, the presence of AlkJ appeared to be necessary. 
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