Abstract:
The present invention relates to a method for producing retinoid from a microorganism, and more specifically, to a method for effectively obtaining retinoid, which lacks stability, from a microorganism by cultivating the microorganism capable of producing retinoid in a medium containing a lipophilic substance, and separating retinoid from the lipophilic substance.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a National Phase application under 35 U.S.C. §371 of International Application No. PCT/KR2012/006071, filed Jul. 30, 2012, which claims priority to and the benefit of Republic of Korea Patent Application Nos. 10-2011-0075715 filed Jul. 29, 2011 and 10-2012-0083185 filed Jul. 30, 2012, the disclosures of which are incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a method for production of retinoid from a microorganism with retinoid producing efficacy. 
     2. Description of the Related Art 
     Retinoid belongs to a class of lipophilic isoprenoid molecules chemically associated with vitamin A. The retinoid includes β-inone cyclic and polyunsaturated branched chains, together with alcohol (e.g., retinol), aldehyde (e.g., retinal), carboxylic acid (e.g., retinoic acid) or ester (e.g., retinyl acetate) functional groups. It is well known that such functional groups play an essential role in health care of a human body such as eyesight protection, bone growth and regeneration, anti-oxidation effects and prevention of skin aging, and may also reduce danger of cancer. 
     In recent years, the retinoid has attracted a great interest as an efficient raw material for cosmetics and medicaments useful for wrinkle improvement and treatment of skin disease. A scale of retinoid market is estimated at about 16 billion dollars over the world. Chemically synthesized retinoid is a representative raw material commercially available in the market. Retinol is produced by acidification or hydrolysis of retinal which was chemically synthesized through reduction of a pentadiene derivative. However, such a chemical process as described above entails disadvantages such as complicated purification processes and generation of undesirable byproducts. An animal creates retinoid using carotinoid obtained from fruits and vegetables, while a plant cannot synthesize retinoid. An overall path of retinoid synthesis is possibly embodied only in a specific microorganism that contains bacteriorhodopsin or proteorhodopsin having retinal as a prosthetic group. Nevertheless, the microorganism generates a protein combination form of retinal, thus not being preferable in mass production of free retinoids. Until now, although partially restricted attempts using enzymes for biological production have been executed, these have not yet gained successful results. Accordingly, there is still a need for development of a biotechnological method using metabolically transformed microorganisms in order to produce retinoid. 
     The retinoid is chemically unstable due to a conjugated and active double bond, and easily oxidized and becomes isomeric by heat, oxygen and light. Further, the retinoid is liable to be degraded through retinoic acid in biological aspects. Accordingly, an effective method for production of retinoid has yet to be developed. 
     SUMMARY 
     Therefore, an object of the present invention is to provide a method for effectively producing retinoid from a microorganism. 
     According to an aspect of the present invention, there is provided a method for production of retinoid from a microorganism, including: culturing a microorganism having retinoid producing efficacy in a medium containing a lipophilic substance; and isolating retinoid from the lipophilic substance phase. 
     The method may include culturing the microorganism having retinoid producing efficacy in a medium containing a lipophilic substance. 
     The term “microorganism” used herein may include a cell possible cultured in a liquid medium. The microorganism may include prokaryote cells, eukaryote cells or isolated animal cells, which are possibly cultured in a liquid medium. Such microorganisms may include, for example, bacteria, fungi or a combination thereof. Bacteria may include, for example, gram positive bacteria, gram negative bacteria or a combination thereof. The gram negative bacteria may include species of the genus  Escherichia . The gram positive bacteria may include species of the genus  bacillus , genus  corynebacterium, lactobacillus  or a combination thereof. The fungi may include yeast,  kluyveromyces  or a combination thereof. The microorganism may have natural or foreign genes introduced therein. The foreign gene may be a gene in association with production of retinoid such as at least one gene in an MEP or MVA path. The animal cell may include cells used for production of recombinant proteins. For instance, CHO cell, BHK cell or a combination thereof may be included. 
     The microorganism of the genus  Escherichia  having retinoid producing efficacy may include microorganisms of the genus of natural or transformed  Escherichia . The microorganism in the natural genus  Escherichia  is known to have the MEP path as an inherent path for retinoid synthesis. The microorganism in the transformed genus  Escherichia  may include genes associated with an inherent MEP path for retinoid synthesis, genes associated with a foreign MVA path for retinoid synthesis or a combination thereof, which are introduced therein. The MVA path gene may be a gene encoding an enzyme in a foreign mevalonate path in association with production of IPP from acetyl-CoA. Alternatively, a strain into which a gene encoding an enzyme associated with synthesis of β-carotene from the above IPP has been introduced may also be included. Further, the foregoing microorganism may be one having at least two copies of IPP isomerases introduced therein, which in turn, shows promoted conversion from IPP to DMAPP. Therefore, the microorganism may the retinoid at a high concentration.  FIG. 1  is a view schematically illustrating an MEP path and a foreign MVA path of retinal biosynthesis. 
     The microorganism in the natural genus  Escherichia  may include, for example,  Escherichia coli . Such genus  Escherichia coli  may include, for example, DH5α, MG1655, BL21 (DE), S17-1, XL1-Blue, BW25113 or a combination thereof. 
     The microorganism in the transformed genus  Escherichia  may be one transformed into, for example: a gene encoding acetyl-CoA acetyl transferase/hydroxymethylglutaryl(HMG)-CoA reductase derived from  Enterococcus faecalis , which is defined by SEQ. ID No. 1; a gene encoding HMG-CoA synthase derived from  Enterococcus faecalis , which is defined by SEQ. ID No. 2; a gene encoding mevalonate kinase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 3; a gene encoding phosphomevalonate kinase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 4; a gene encoding mevalonate diphosphate decarboxylase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 5; a gene encoding isopentinyl diphosphate (IPP) isomerase derived from  Escherichia coli , which is defined by SEQ. ID No. 6; a gene encoding geranylgeranyl pyrophosphate (GGPP) synthase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 7; a gene encoding phytoene synthase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 8; a gene encoding phytoene dehydrogenase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 9; and a gene encoding lycopene β-cyclase derived from  Pantoea ananatis , which is defined by SEQ. ID No. 10. 
     The microorganism in the transformed genus  Escherichia  may be one transformed into any one of the genes defined by SEQ. ID Nos. 1 to 10, and may be further transformed into at least one selected from a group consisting of, for example: a gene encoding β-carotene monooxygenase derived from uncultured marine bacterium 66A03, which is defined by SEQ. ID No. 13; a gene encoding β-carotene 15,15′-monooxygenase derived from  Mus musculus , which is defined by SEQ. ID No. 14; a gene encoding brp-like protein 2 (brp 2) derived from  Natronomonas pharaonis  ATCC35678, which is defined by SEQ. ID No. 15; and a gene encoding β-carotene monooxygenase derived from  Halobacterium salinarum  ATCC700922, which is defined by SEQ. ID No. 16 or 17, or the like. 
     The microorganism described above may produce retinoid further transformed into a gene encoding IPP isomerase derived from  Haematococcus pluvialis , which is defined by SEQ. ID No. 12. 
     The microorganism having retinoid producing efficacy may be transformed into a gene encoding 1-deoxyxylolose-5-phosphate (DXP) synthase (dxs) derived from  Escherichia coli , which is defined by SEQ. ID No. 11. Since DXP is an enzyme corresponding to a process of determining a velocity in an inherent MEP path, the above microorganism can produce β-carotene at a high concentration by further introducing a gene encoding DXP synthase. 
     If the microorganism having retionid producing efficacy of the present invention belongs to the genus  Escherichia , it may be, for example,  Escherichia coli  DH5α/pTDHB/pSNA with Accession No. KCTC 11254BP (Korean collection for type culture, deposited on Jan. 2, 2008) or  Escherichia coli  DH5α/pTDHBSR/pSNA with Accession No. KCTC 11255BP (Korean collection for type culture, deposited on Jan. 2, 2008). In particular, or  Escherichia coli  DH5α/pTDHBSR/pSNA can produce retinoid with high productivity from a carbon source in a medium. The microorganisms,  Escherichia coli  DH5α/pTDHB/pSNA and  Escherichia coli  DH5α/pTDHBSR/pSNA, were duly deposited with Korean Collection for Type Cultures (KCTC) (having the address of Biological Resource Center (BRC), Korea Research Institute of Bioscience and Biotechnology (KRIBB), 52 Eoeun-dong, Yuseong-gu, Daejeon 305-333, Republic of Korea) under the Access numbers of KCTC11254BP and KCTC 11255BP, respectively, on Jan. 2, 2008. The deposits have been made under the terms of the Budapest Treaty and all restrictions imposed by the depositor on the availability to the public of the biological material will be irrevocably removed upon the granting of a patent. 
     According to one embodiment, the microorganism described above may be a microorganism in the genus  Escherichia  transformed into, for example: a gene encoding acetyl-CoA acetyltransferase/hydroxymethylglutaryl (HMG)-CoA reductase derived from  Enterococcus faecalis , which is defined by SEQ. ID No. 1; a gene encoding HMG-CoA synthase derived from  Enterococcus faecalis , which is defined by SEQ. ID No. 2; a gene encoding mevalonate kinase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 3; a gene encoding phosphomevalonate kinase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 4; a gene encoding mevalonate diphosphate decarboxylase derived from  Streptococcus pneumoniae , which is defined by SEQ. ID No. 5; a gene encoding isopentinyl diphosphate (IPP) isomerase derived from  Escherichia coli , which is defined by SEQ. ID No. 6; a gene encoding geranylgeranyl pyrophosphate (GGPP) synthase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 7; a gene encoding phytoene synthase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 8; a gene encoding phytoene dehydrogenase derived from  Pantoea agglomerans , which is defined by SEQ. ID No. 9; a gene encoding lycopene β-cyclase derived from  Pantoea ananatis , which is defined by SEQ. ID No. 10; a gene encoding 1-deoxyxylolose-5-phosphate (DXP) synthase (dxs) derived from  Escherichia coli , which is defined by SEQ. ID No. 11; and a gene encoding IPP isomerase derived from  Haematococcus pluvialis , which is defined by SEQ. ID No. 12. More particularly, such a microorganism in the genus  Escherichia  as described above may be a microorganism in the genus  Escherichia  further transformed into at least one gene selected from a group consisting of, for example: a gene encoding β-carotene monooxygenase derived from uncultured marine bacterium 66A03, which is defined by SEQ. ID No. 13; a gene encoding β-carotene 15,15′-monooxygenase derived from  Mus musculus , which is defined by SEQ. ID No. 14; a gene encoding brp-like protein 2 (brp 2) derived from  Natronomonas pharaonis  ATCC35678, which is defined by SEQ. ID No. 15; and a gene encoding β-carotene monooxygenase derived from  Halobacterium salinarum  ATCC70922, which are defined by SEQ. ID Nos. 16 and 17. The gene encoding β-carotene monooxygenase derived from uncultured marine bacterium 66A03, which is defined by SEQ. ID No. 13, may have a base sequence defined by SEQ. ID No. 32, which is codon-optimized in  Escherichia coli.    
     In the present text, the term “retinoids” means a species of chemical substances chemically associated with vitamin A. The retinoid may have a structure consisting of a cyclic end group, polyene branched chain and polar end group. A conjugate system formed by alternately aligning C═C double bonds in the polyene branched chain may express color of the retinoid (usually yellow, orange or red color). Most of retinoids are chromophore. By altering the branched chain and end groups, a variety of retinoids may be produced. Such retinoids may include retinal, retinol, retinoic acid, retinyl acetate or a combination thereof. Further, the retinoid may include any product of in vivo degradation of retinal, retinol, retinoic acid, retinyl acetate or a combination thereof. 
     The retinoid is a material having 20 basic carbon atoms and, according to fatty acid prosthetic groups bonded thereto, the final number of carbon atoms may be changed. For instance, in case of acetate bonding, the final number of carbon atoms is 22. On the other hand, for oleic acid bonding, the final number of carbon atoms may be 38. 
     The lipophilic substance described above may be an organic compound having 8 to 50 carbon atoms with lipophilic properties. 
     The lipophilic substance may include, for example, an alkane compound having 8 to 50 carbon atoms, a compound represented by Formula 1 below, a compound represented by Formula 2 below, or a combination thereof.
 
R 1 (CO)OR 2   [Formula 1]
 
     (wherein R 1  and R 2  are each independently alkyl having 8 to 50 carbon atoms, and CO represents a carbonyl group). 
     
       
                 
         
             
             
         
      
     
     (wherein R 3 , R 4  and R 5  are each independently alkyl having 8 to 50 carbon atoms, and CO represents a carbonyl group). 
     The alkane compound having 8 to 50 carbon atoms may be straight alkane, brached alkane, cyclic alkane or a combination thereof. The alkane compound may include compounds having carbon atoms in a range of, for example: 8 to 46; 8 to 40; 8 to 36; 8 to 30; 8 to 26; 8 to 20; 8 to 16; 8 to 12; 8 to 10; 10 to 50; 10 to 46; 10 to 40; 10 to 36; 10 to 30; 10 to 26; 10 to 20; 10 to 17; to 12; 10 to 50; 10 to 46; 12 to 50; 12 to 46; 12 to 36; 12 to 30; 12 to 26; 12 to 20; or 12 to 16. 
     The straight alkane may include alkanes having 8 carbon atoms (octane), 10 carbon atoms (decane), 12 carbon atoms (dodecane), 14 carbon atoms (tetradecane), or alkanes having 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 carbon atoms, or a combination thereof. 
     The branched alkane may include alkanes having 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 carbon atoms, or a combination thereof. The branched alkane may include saturated analogues of a terpene compound. For instance, phytosqualane may be included. 
     A combination of the straight alkane, branched alkane and cyclic alkane may be mineral oil. The mineral oil may be a mixture of alkanes having 15 to 40 carbon atoms, which are derived from non-vegetable raw materials (mineral). The alkane having 15 to 40 carbon atoms may include, for example, at least two mixtures of alkanes having 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39 or 40 carbon atoms. 
     The mineral oil may be lightweight or heavy mineral oil. The lightweight mineral oil is a substance generally having a density of 880 to 920 kg/m 3 , a specific gravity of 820 to 860 kg/m 3  at 20° C., and a fluid viscosity of 14 to 18 cst at 40° C. On the other hand, the heavy mineral oil is a substance generally having a density of 920 kg/m3, a specific gravity of 860 to 900 kg/m 3  at 20° C., and a fluid viscosity of 65 to 85 cst at 40° C. 
     In the compound represented by Formula 1, R 1  and R 2  are each independently straight, branched or cyclic alkyl having 8 to 50 carbon atoms. Herein, R 1  and R 2  may be each independently alkyl having 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 carbon atoms. 
     R 1  and R 2  may be each independently alkyl having carbon atoms in a range of 8 to 50, for example: 8 to 46; 8 to 40; 8 to 36; 8 to 30; 8 to 26; 8 to 20; 8 to 16; 8 to 12; 8 to 10; 10 to 50; 10 to 46; 10 to 40; 10 to 36; 10 to 30; 10 to 26; 10 to 20; 10 to 16; 10 to 12; 10 to 50; 10 to 46; 12 to 50; 12 to 46; 12 to 36; 12 to 30; 12 to 26; 12 to 20; or 12 to 16. R 1  may be a straight alkyl having 13 carbon atoms while R 2  is isopropyl. Further, R 1  may be ethylpentyl while R 2  is cetyl. 
     In the compound represented by Formula 2, R 3 , R 4  and R 5  are each independently straight, branched or cyclic alkyl having 8 to 50 carbon atoms. 
     R 3 , R 4  and R 5  may be each independently alkyl having 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48 or 50 carbon atoms. The foregoing compound may contain R 3 , R 4  and R 5 , which are each independently alkyl having carbon atoms in a range of 8 to 50, for example: 8 to 46; 8 to 40; 8 to 36; 8 to 30; 8 to 26; 8 to 20; 8 to 16; 8 to 12; 8 to 10; 10 to 50; to 46; 10 to 40; 10 to 36; 10 to 30; 10 to 26; 10 to 20; 10 to 16; 10 to 12; 10 to 50; 10 to 46; 12 to 50; 12 to 46; 12 to 36; 12 to 30; 12 to 26; 12 to 20; or 12 to 16. 
     The lipophilic substance may include, for example, octane, decane, dodecane, tetradecane, phytosqualane, mineral oil, isopropyl myristate, cetyl ethylhexanoate, dioctanoyl decanoyl glycerol, squalane, or a combination thereof. 
     The lipophilic substance may not only stabilize produced retinoids but also increase productivity of the retinoids by microorganisms. The lipophilic substance does not affect growth of microorganisms or may slightly influence on the same. 
     Culture may be performed in a synthetic, semi-synthetic or combined culture medium. Such a culture medium may include, for example, a medium consisting of a carbon source, nitrogen source, vitamin and mineral. For instance, a Man-Rogosa-Sharp (MRS) liquid medium or a milk-added liquid medium may be used. 
     The carbon source of the medium may include starch, dextrose, sucrose, galactose, fructose, glycerol, glucose, or a mixture thereof. For instance, glycerol may be used as the carbon source. The nitrogen source may include ammonium sulfate, ammonium nitrate, sodium nitrate, glutamic acid, casaminoic acid, yeast extract, peptone, tryptone, soy bean husk, or a mixture thereof. Mineral may include sodium chloride, potassium (II) phosphate, magnesium sulfate, or a mixture thereof. 
     When the culturing is executed in a fermentation tank, glucose is preferably used as a carbon source. For test tube culture, glycerol is preferably used as a carbon source. 
     The carbon source, nitrogen source and mineral in the medium for culturing microorganisms are used in an amount of 10 to 100 g, 5 to 40 g and 0.5 to 4 g, respectively, to 1 liter. 
     Vitamin added to a typical culture medium under general culture conditions of  Escherichia coli  may be vitamin A, vitamin B, vitamin C, vitamin D, vitamin E or a mixture thereof. The vitamin may be added to the typical culture medium together with such carbon source, nitrogen source and/or mineral as described above. Otherwise, the vitamin may be alternatively added to a sterilized medium. 
     The culturing may be executed under general culture conditions. The culturing may be executed at a temperature in a range of 15 to 45° C., for example, 15 to 44° C.; 15 to 43° C.; 15 to 42° C.; 15 to 41° C.; 15 to 40° C.; 15 to 39° C.; 15 to 38° C.; 15 to 37° C.; 15 to 36° C.; 15 to 35° C.; 15 to 34° C.; 15 to 33° C.; 15 to 32° C.; 15 to 31° C.; 15 to 30° C.; 20 to 45° C.; 20 to 44° C.; 20 to 43° C.; 20 to 42° C.; 20 to 41° C.; 20 to 40° C.; 20 to 39° C.; 20 to 38° C.; 20 to 37° C.; 20 to 36° C.; 20 to 35° C.; 20 to 34° C.; 20 to 33° C.; 20 to 32° C.; 20 to 31° C.; 20 to 30° C.; 25 to 45° C.; 25 to 44° C.; 25 to 43° C.; 25 to 42° C.; 25 to 41° C.; 25 to 40° C.; 25 to 39° C.; 25 to 38° C.; 25 to 37° C.; 25 to 36° C.; 25 to 35° C.; 25 to 34° C.; 25 to 33° C.; 25 to 32° C.; 25 to 31° C.; 25 to 30° C.; 27 to 45° C.; 27 to 44° C.; 27 to 43° C.; 27 to 42° C.; 27 to 41° C.; 27 to 40° C.; 27 to 39° C.; 27 to 38° C.; 27 to 37° C.; 27 to 36° C.; 27 to 35° C.; 27 to 34° C.; 27 to 33° C.; 27 to 32° C.; 27 to 31° C.; or 27 to 30° C. 
     In order to collect or recover concentrated strain after removing the culture medium in a culture solution, centrifugation or filtration may be conducted. Such a process may be optionally executed according to demands of those skilled in the art. By freezing or freeze-drying the concentrated strain according to any conventional method, activities of the strain may be retained. 
     According to one example of the culturing, the culturing may be performed in a medium containing glycerol as a carbon source. Glycerol may be only the carbon source in the medium. The culturing may be conducted in a medium containing glycerol in an amount of 0.5 to 5.0% (w/v), for example: 0.5 to 4.5% (w/v); 0.5 to 4.0% (w/v); 0.5 to 3.5% (w/v); 0.5 to 3.0% (w/v); 0.5 to 2.5% (w/v); 0.5 to 2.0% (w/v); 0.5 to 1.5% (w/v); 1 to 4.5% (w/v); 1 to 4.0% (w/v); 1 to 3.5% (w/v); 1 to 3.0% (w/v); or 1 to 2.5% (w/v). Such a medium may be an YT medium including glycerol and arabinose added thereto. The YT medium may include 1.6 wt. % of tryptone, 1 wt. % of yeast extract and 0.5 wt. % of NaCl. 
     The culturing may be performed in a culture medium in the presence of a lipophilic substance while placing a dodecane phase formed of a lipophilic substance on the surface of the medium. The culturing may be performed under agitation. 
     The agitation may be conducted at a range of 100 to 300 rpm, for example, 100 to 280 rpm, 100 to 260 rpm, 100 to 240 rpm, 100 to 220 rpm, 100 to 200 rpm, 100 to 180 rpm, 100 to 160 rpm, 100 to 140 rpm, 100 to 120 rpm, 120 to 300 rpm, 120 to 280 rpm, 120 to 260 rpm, 120 to 240 rpm, 120 to 220 rpm, 120 to 200 rpm, 120 to 180 rpm, 120 to 160 rpm, 120 to 140 rpm, 150 to 300 rpm, 150 to 280 rpm, 150 to 260 rpm, 150 to 240 rpm, 150 to 220 rpm, 150 to 200 rpm, 150 to 180 rpm, 140 to 160 rpm, 200 to 300 rpm, 200 to 280 rpm, 200 to 260 rpm, 200 to 240 rpm, 200 to 220 rpm, or 150 rpm. 
     In case of agitating, the lipophilic substance, that is, dodecane may be dispersed in the medium and contact with cells. Since the lipophilic substance is dispersed in the medium to increase a microorganism-contacting area, retinoid may be efficiently isolated from the cells during culturing, thereby enabling stabilization and dissolution of the retinoid. 
     When a microorganism for producing retinoids was cultured without the lipophilic substance, that is, the dodecane phase, the production of retinoids may reach a maximum level at a constant time and, thereafter, become decrease. The reason of such facts may be because a further synthesis of retinoid is stopped during the growth of microorganism has stagnated, while occurring intracellular oxidative degradation of the retinoid. 
     If the microorganism is cultured in a culture medium in the presence of the lipophilic substance, that is, dodecane phase, the produced retinoid may be absorbed in to the lipophilic substance, that is, dodecane phase before the retinoid is degraded in the cell, thereby improving productivity of retinoid. 
     The lipophilic substance, that is, dodecane phase does not affect upon the cellular growth of a microorganism in the genus  Escherichia , instead, may be hydrophobic and used for extracting the retinoid and have a low volatility.  FIG. 2  illustrates conversion of β-carotene into retinoids including retinal, retinol, retinoic acid and retinyl ester. 
     A ratio by volume of medium to lipophilic substance may be, for example: 1:0.1 to 3.0, 1:0.5 to 3.0, 1:1.0 to 3.0, 1:1.5 to 3.0, 1:2.0 to 3.0, 1:2.5 to 3.0, 1:0.2 to 2.5, 1:0.2 to 2.0, 1:0.2 to 1.5, 1:0.2 to 1.0, 1:0.2 to 0.5, 1:0.5 to 2.5, 1:0.5 to 2.0, 1:0.5 to 1.5, 1:0.5 to 1.0, 1:0.8 to 2.5, 1:0.8 to 2.0, 1:0.8 to 1.5, 1:0.8 to 1.2, 1:0.8 to 1.0, or the like. 
     According to one embodiment, the medium may contain glycerol at a concentration of about 2.0% during culturing, the microorganism in the genus  Escherichia  may be  Escherichia coli  DH5α or MG1655, and the culturing may include culturing using 7 ml of a culture solution at about 29° C. 
     The foregoing method may include isolating retinoid from a lipophilic substance phase. A method for isolation of the retinoid including, for example, retinal, retinol, retinoic acid, retinyl ester or a combination thereof is well known in the art. For example, the retinoid may be isolated by a conventional method such as ion exchange chromatography, HPLC or the like. For instance, in order to obtain a high purity product after recovering a strain and extracting the same using a solvent such as acetone, separation and purification through HPLC or crystallization may be conducted. 
     A method for production of retinoid from a microorganism in the genus  Escherichia  according to one embodiment of the present invention may include: culturing the microorganism having retinoid producing efficacy in the genus  Escherichia , in a medium including a lipophilic substance; and isolating the retinoid from the lipophilic substance phase, wherein the lipophilic substance is an alkane compound having 8 to 50 carbon atoms, a compound represented by Formula 1, a compound represented by Formula 2 or a combination thereof. 
     The method for production of retinoid according to the present invention may produce retinol with high efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view schematically illustrating an MEP path and a foreign MVA path of retinal biosynthesis; 
         FIG. 2  illustrates retinoid conversion of β-carotene into retinoid including retinal, retinol, retinoic acid and retinyl ester. 
         FIG. 3  illustrates production of retinal, production of β-carotene and cell growth of  Escherichia coli  including pT-HB, pT-HBblh, pT-HPbrp, pT-HBbrp2, pT-HBBCMO1 and pT-HBSR; 
         FIG. 4  illustrates production of retinal, production of β-carotene and cell growth of  Escherichia coli  including pT-HB, pT-HBSR, pT-DHB and pT-DHBSR, as well as  Escherichia coli  including pT-DHB or pT-DHBSR together with pS-NA as an MVA path plasmid; 
         FIG. 5  illustrates retinoid production and cell growth by a variety of  Escherichia coli  strains including pT-DHBSR and pS-NA; 
         FIG. 6  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on a test volume of a culture solution; 
         FIG. 7  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on a culture temperature; 
         FIG. 8  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on a carbon source; 
         FIGS. 9 and 10  illustrate retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on a concentration of glycerol as a carbon source, respectively; and 
         FIGS. 11 and 12  illustrate results of retinoid production and cell growth by a variety of  Escherichia coli  strains in the presence of dodecane, respectively. 
         FIG. 13  illustrates retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) depending on a concentration of glycerol as a carbon source in a 2-phase culture system including 1 mL of dodecane in 5 ml of culture medium; 
         FIG. 14  illustrates retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) in a 2-phase culture system depending on the volume of dodecane; 
         FIG. 15  illustrates distributions of retinoid depending on a culturing time of  Escherichia coli  (pT-DHBSR/pS-NA) and a volume of dodecane in a 2-phase culture system, which are represented in terms of percentages of individual constituents to total retinoid; 
         FIG. 16  illustrates effects of dodecane addition upon production of beta-carotene and cell growth of  Escherichia coli  including pT-DHB and pS-NA; 
         FIGS. 17 and 18  illustrate results of retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) in the presence of different alkanes, respectively; 
         FIGS. 19, 20 and 21  illustrate results of retinoid production, cell growth, and cell specific retinoids productivity of  Escherichia coli  (pT-DHBSR/pS-NA) in the presence of different volumes of lightweight mineral oil, respectively; 
         FIGS. 22 and 23  illustrate results of retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) in the presence of heavy mineral oil, respectively; 
         FIGS. 24 and 25  illustrate results of retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) when culturing was conducted by tilting a test tube, respectively; 
         FIG. 26  illustrates cell growth and pH of  Escherichia coli  (pT-DHBSR/pS-NA) in the presence of skin-friendly lipophilic substance; and 
         FIGS. 27 and 28  illustrate results of retinoid production of  Escherichia coli  depending on different kinds and amounts of skin-friendly lipophilic substance, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the present invention will be described in more details according to the following examples. However, these examples are proposed for illustrative purposes only and the scope of the present invention is not particularly limited thereto. In the examples, the following experimental materials and methods have been used. 
     Bacteria Strain and Culture Conditions 
       Escherichia coli  DH5α was used for gene cloning and retinoid production. Alternatively,  Escherichia coli  MG1655, BL21 (DE3), XL1-Blue, S17-1 and BW25113 were used to investigate an optimum strain for retinol production. The culture for retinoid production was executed in a 2YT medium (including 16 g of tryptone, 10 g of yeast extract and 5 g of NaCl per liter) at 29° C. using an agitation incubator operating at 250 rpm. A major and additional carbon sources were glycerol and arabinose, which were added in concentrations of 0.5 to 2% (w/v) and 0.2% (w/v), respectively, to the incubator. Alternative carbon sources for retinoid production, for example, glucose, galactose, xylose and maltose were compared to glycerol. Ampicillin (100 μg/mL) and chloramphenicol (50 μg/mL) were optionally added to a culture solution requiring the same. The culturing was conducted in a test tube containing 7 ml of medium. Cell growth was determined by measuring an optical density at 600 nm (OD 600 ). In a 2-phase culture method for production of retinoid, 1 mL of dodecane (Cat. No. 297879, Sigma, USA) was placed on 5 ml of the culture medium. 
     Conditions for Analysis of β-Carotene and Retinoid 
     β-carotene and retinoid were extracted from bacteria cell pellets through acetone. In the 2-phase culture method including dodecane capping, cell pieces were completely removed by collecting a dodecane phase containing retinoid and centrifuging the same at 14,000 rpm for 10 minutes. The acetone extraction product and dodecane phase were analyzed using HPLC (LC-20A, Shimadzu, Kyoto, Japan) at detection wavelengths of 370 nm (retinal), 340 nm (retinol and retinyl acetate) and 454 nm (β-carotene). The analysis was performed using a Symmetry C18 type (250 mm×4.6 mm, 5 m) HPLC column including Sentry Guard C18 (15 mm×4.6 mm, 5 m). A mobile phase of the column was each of methanol and acetonitrile in ratios of 95:5 and 70:30, respectively, for analyzing retinoid and β-carotene. HPLC analysis was performed at a flow rate of 1.5 ml/min and a column temperature of 40° C. Retinal (Cat. No. R2500), retinol (Cat. No. R7632), retinyl acetate (Cat. No. R4632) and β-carotene (Cat. No. C4582) were purchased from Sigma Co. (USA) and dissolved in acetone, respectively, to prepare standard compounds, and each of the prepared standard compounds was used. Through three independent experiments, results were obtained and represented by a mean±SD. 
     EXAMPLE 1 
     Preparation of Vector for Producing  Escherichia coli  with High Productivity of β-Carotene and Retinal 
     Conventional processes involving genome DNA preparation, restriction enzyme cleavage, transformation and standard molecular biological technologies have been executed according to description in related documents (Sambrook and Russell 2001). PCR was performed using pfu DNA polymerase according to standard protocols (Solgent Co., Korea). blh gene of uncultured marine bacteria 66A03 (Genbank accession No. AAY68319) was synthesized into Genofocus (Daejeon, Korea) according to codon-optimization by Gene Designer software (DNA 2.0, Menlo Park, USA), in order to express the above gene in  Escherichia coli.    
     According to the present example, an enzyme involved in a velocity determination process, that is, a gene encoding DXP synthase was additionally introduced into  Escherichia coli  having an MEP path and, at the same time, a gene encoding an enzyme associated with a mevalonate path was selected from a variety of gene resources and introduced, thus preparing  Escherichia coli  with high productivity of β-carotene. 
     (1) Preparation of pSNA Vector Including a Gene Encoding an Enzyme in a Mevalonate Path Associated with Synthesis of IPP from a Carbon Source 
     Genes encoding an enzyme in a mevalonate path associated with IPP synthesis from a carbon source used in the present experiment are shown in Table 1 below. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                 Gene sequence 
               
               
                   
                   
                 (Genbank 
               
               
                 Name of enzyme 
                 Gene 
                 accession No.) 
               
               
                   
               
             
             
               
                 Acetyl-CoA 
                 mvaE 
                 SEQ. ID No. 18 
               
               
                 acetyltransferase/hydroxymethylglytaryl 
                   
                 (AF290092) 
               
               
                 (HMG)-CoA reductase derived from 
               
               
                 
                   Enterococcus faecalis 
                 
               
               
                 HMG-CoA synthase derived from 
                 mvaS 
                 SEQ. ID No. 19 
               
               
                 
                   Enterococcus faecalis 
                 
                   
                 (AF290092) 
               
               
                 Mevalonate kinase derived from 
                 mvaK1 
                 SEQ. ID No. 20 
               
               
                 
                   Streptococcus pneumonia 
                 
                   
                 (AF290099) 
               
               
                 Phosphomevalonate kinase derived from 
                 mvaK2 
                 SEQ. ID No. 21 
               
               
                 
                   Streptococcus pneumonia 
                 
                   
                 (AF290099) 
               
               
                 Mevalonate diphosphate decarboxylase 
                 mvaD 
                 SEQ. ID No. 22 
               
               
                 derived from  Streptococcus pneumoniae   
                   
                 (AF290099) 
               
               
                 Isopentenyl diphosphate (IPP) isomerase 
                 Idi 
                 SEQ. ID No. 23 
               
               
                 derived from  Escherichia coli   
                   
                 (U00096) 
               
               
                   
               
             
          
         
       
     
     Primers and restriction enzymes to amplify genes listed in Table 1 have been described. 
     
       
         
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Restriction 
               
               
                   
                 Primer sequence 
                 enzyme 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 mvaE 
                 F 
                 SEQ. ID No. 37 
                 SacI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 38 
                 SmaI 
               
               
                   
                 mvaS 
                 F 
                 SEQ. ID No. 39 
                 SmaI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 40 
                 BamHI 
               
               
                   
                 mvaK1, mvaK2, 
                 F 
                 SEQ. ID No. 41 
                 KpnI 
               
               
                   
                 mvaD 
                 R 
                 SEQ. ID No. 42 
                 XbaI 
               
               
                   
                 Idi 
                 F 
                 SEQ. ID No. 43 
                 SmaI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 44 
                 SphI 
               
               
                   
                   
               
             
          
         
       
     
     The primer sequences and restriction enzymes used in cloning the genes listed in Table 1 are stated in Table 2. Since mvaK1, mvaK2 and mvaD are present as a single operon in a chromosome, a whole operon rather than individual genes was subjected to PCR cloning at once. 
     The genes listed in Table 1 were amplified using the primers listed in Table 3 through PCR which uses a chromosome DNA in each strain including corresponding gene as a matrix. The amplified product was introduced into pSTV28 vector (Takara Korea, Korea) (SEQ. ID No. 45) using the restriction enzymes listed in Table 2, thereby preparing the vector pSNA. The vector pSNA includes all of genes encoding the enzyme in a mevalonate path, which can produce IPP from acetyl-CoA. 
     (2) Preparation of Vectors pT-HB and pT-DHB Including a Gene Encoding an Enzyme Associated with Synthesis of β-Carotene from IPP 
     Genes encoding an enzyme associated with synthesis of β-carotene from IPP used in the present experiment, as well as DXP synthase gene as an enzyme involved in the velocity determination process in the MEP path, are shown in Table 3 below. 
     
       
         
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                 Gene sequence 
               
               
                   
                   
                 (Genbank 
               
               
                 Name of enzyme 
                 Gene 
                 accession No.) 
               
               
                   
               
             
             
               
                 IPP isophomerase derived from 
                 ipiHpl 
                 SEQ. ID No. 24 
               
               
                 
                   Haematococcus pluvialis 
                 
                   
                 (AF082325) 
               
               
                 1-deoxyxylolose-5-phosphate (DXP) 
                 dxs 
                 SEQ. ID No. 25 
               
               
                 synthase derived from  Escherichia coli   
                   
                 (U00096) 
               
               
                 Geranylgeranyl pyrophosphate (GGPP) 
                 crtE 
                 SEQ. ID No. 26 
               
               
                 synthase derived from  pantoea agglomerans   
                   
                 (M87280) 
               
               
                 Phytoene synthase derived from  pantoea   
                 crtB 
                 SEQ. ID No. 27 
               
               
                 
                   agglomerans 
                 
                   
                 (M87280) 
               
               
                 Phytoene dehydrogenase derived from 
                 crtI 
                 SEQ. ID No. 28 
               
               
                 
                   pantoea agglomerans 
                 
                   
                 (M87280) 
               
               
                 Lycopene β-cyclase derived from  pantoea   
                 crtY 
                 SEQ. ID No. 29 
               
               
                 
                   ananatis 
                 
                   
                 (D90087) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                   
                 Restriction 
               
               
                   
                 Gene 
                 Primer sequence 
                 enzyme 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 ipiHpl 
                 F 
                 SEQ. ID No. 46 
                 SmaISphI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 47 
               
               
                   
                 dxs 
                 F 
                 SEQ. ID No. 48 
                 EcoR1SnaBI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 49 
               
               
                   
                 crtE 
                 F 
                 SEQ. ID No. 50 
                 BspHIEcoRI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 51 
               
               
                   
                 crtB, crtI 
                 F 
                 SEQ. ID No. 52 
                 EcoR1SacI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 53 
               
               
                   
                 crtY 
                 F 
                 SEQ. ID No. 54 
                 SalIPstI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 55 
               
               
                   
                   
               
             
          
         
       
     
     The primer sequences and restriction enzymes used in cloning the genes listed in Table 3 are stated in Table 4. Since crtB and crtI are present as a single operon in a chromosome, a whole operon rather than individual genes was subjected PCR cloning at once. 
     The genes listed in Table 3 were amplified using the primers listed in Table 4 through PCR which uses a chromosome DNA in each strain including corresponding gene as a matrix. The amplified product was introduced into pTrc99A vector (Genbank accession No. M22744) (SEQ. ID No. 30) using the restriction enzymes listed in Table 4, thereby preparing the vector pT-DHB. The vector pTDHB includes all of genes encoding the enzyme associated with synthesis of β-carotene from IPP, as well as DXP synthase (dxs) gene as an enzyme used in the velocity determination process in the MEP path. Further, among the genes listed in Table 3, all genes other than dxs were introduced into pTrc99A vector using the restriction enzymes listed in Table 4, thereby preparing the vector pT-HB. 
     (3) Preparation of a Vector Including a Gene Encoding an Enzyme Associated with Synthesis of Retinal from β-Carotene 
     Genes encoding an enzyme associated with synthesis of retinal from β-carotene used in the present experiment are shown in Table 5 below. As a gene encoding β-carotene monooxygenase derived from uncultured marine bacterium 66A03, SR gene which is an  Escherichia coli  codon-optimized sequence of blh was used. 
     
       
         
               
               
               
             
           
               
                 TABLE 5 
               
               
                   
               
               
                   
                   
                 Gene sequence 
               
               
                   
                   
                 (Genbank 
               
               
                 Name of enzyme 
                 Gene 
                 accession No.) 
               
               
                   
               
             
             
               
                 β-carotene monooxygenase derived 
                 blh 
                 SEQ. ID No. 31 
               
               
                 from uncultured marine bacterium 
                   
                 (DQ065755) 
               
               
                 66A03 
               
               
                 β-carotene monooxygenase derived 
                 SR 
                 SEQ. ID No. 32 
               
               
                 from uncultured marine bacterium 
                 ( Escherichia   
               
               
                 66A03 
                 
                   coli 
                 
               
               
                   
                 codon- 
               
               
                   
                 optimized 
               
               
                   
                 sequence 
               
               
                   
                 of blh) 
               
               
                 β-carotene 15,15′-monooxygenase 
                 BcmoI 
                 SEQ. ID No. 33 
               
               
                 derived from  Mus musculus   
                   
                 (NM_021486) 
               
               
                 Brp-like protein 2 derived from 
                 brp2 
                 SEQ. ID No. 34 
               
               
                   Natronomonas pharaonis  ATCC35678 
                   
                 (CR936257) 
               
               
                 β-carotene monooxygenase derived 
                 Blh 
                 SEQ. ID No. 35 
               
               
                 from  Halobacterium salinarum   
                   
                 (AE004437) 
               
               
                 ATCC700922 
               
               
                 β-carotene monooxygenase derived 
                 Brp 
                 SEQ. ID No. 36 
               
               
                 from  Halobacterium salinarum   
                   
                 (AE004437) 
               
               
                 ATCC700922 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                   
                   
                 Restriction 
               
               
                   
                 Gene 
                 Primer sequence 
                 enzyme 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 SR 
                 F 
                 SEQ. ID No. 56 
                 EcoR1SpeI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 57 
               
               
                   
                 bcmo1 
                 F 
                 SEQ. ID No. 58 
                 EcoR1SpeI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 59 
               
               
                   
                 brp2 
                 F 
                 SEQ. ID No. 60 
                 EcoR1SpeI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 61 
               
               
                   
                 blh 
                 F 
                 SEQ. ID No. 62 
                 EcoR1SpeI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 63 
               
               
                   
                 brp 
                 F 
                 SEQ. ID No. 64 
                 EcoR1SpeI 
               
               
                   
                   
                 R 
                 SEQ. ID No. 65 
               
               
                   
                   
               
             
          
         
       
     
     The primer sequences and restriction enzymes used in cloning the genes listed in Table 5 are stated in Table 6. The genes listed in Table 5 were amplified using the primers listed in Table 6 through PCR which uses a chromosome DNA in each strain including a corresponding gene as a matrix. The amplified product was introduced into pT-HB vector using the restriction enzymes listed in Table 6, respectively, thereby preparing the vectors pT-HBSR, pT-HBBcmo1, pT-HBbrp2, pT-HBblh and pT-HBbrp. Such vectors pT-HBSR, pT-HBBcmo1, pT-HBbrp2, pT-HBblh and pT-HBbrp are vectors formed by introducing SR, Bcmo1, brp2, blh and brp genes into pT-HB vector, respectively, and have included all of genes encoding an enzyme associated with the synthesis of retinal through β-carotene from IPP. After cutting SR gene from pT-HBSR using SpeI, the cut gene was introduced into a corresponding part of pT-DHB, thus preparing pT-DHBSR. 
     EXAMPLE 2 
     Comparison of Different BCM(D)O Genes in Relation to Retinal Production 
     Retinal may be produced by introduction of BCM(D)O gene encoding β-carotene mono(di)oxygenase, which is a recombinant  Escherichia coli  producing β-carotene. The present inventors have conducted cloning of BCM(D)O gene from two bacteria, i.e.,  Halobacterium  sp NRC-1 (blh and brp genes) and  Natronomonas pharaonis  (brp2 gene), as well as  Mus musculus  (Bcmo1 gene) of a vertebrate animal. The present inventors have synthesized codon-optimized BCDO gene (SR) on the basis of an amino acid sequence of uncultured marine bacterium 66A03 blh gene. BCM(D)O gene (SR) was used to prepare retinal synthetic plasmids pT-HBblh, pT-HBbrp, pT-HBbrp2, pT-HBBcmo1 and pT-HBSR, respectively. The recombinant  Escherichia coli  cell containing each of retinal plasmids was cultured in a 2YT medium including 0.5% (w/v) of glycerol and 0.2% (w/v) of arabinose as a carbon source at 29° C. for 48 hours. 
       FIG. 3  illustrates production of retinal, production of β-carotene and cell growth of  Escherichia coli  including pT-HB, pT-HBblh, pT-HBbrp, pT-HBbrp2, pT-HBBCMO1 and pT-HBSR. More particularly, white and grey bars show numerical values at 24 hours and 48 hours, respectively. 
     As shown in  FIG. 3 , the recombinant  Escherichia coli  pT-HBblh, pT-HBbrp and pT-HBSR have produced 2.2, 0.8 or 1.4 mg/L of retinal, respectively, at 24 hours. However, retinal production by the recombinant  Escherichia coli  pT-HBblh or pT-HBbrp was reduced to 0.7 or 0.4 mg/L, respectively, at 48 hours, whereas  Escherichia coli  pT-HBSR showed a slight increase in retinal production. The decrease in retinal production after 24 hours may be caused by oxidative degradation of retinal in the cell. An amount of retinal obtained from the culture solution depends upon both intracellular synthesis and degradation of retinal. 
     For  Escherichia coli  including pT-HBblh or pT-HBbrp, a retinal productivity at 24 hours after culturing may be lower than a rate of degradation of the same. In the culture of  Escherichia coli  strain including pT-HBbrp2 or pT-HBBcmo1, a trace amount of retinal was detected.  Escherichia coli  without BCM(D)O gene has produced 35 mg/L of β-carotene, but did not produce retinal. Since β-carotene is a precursor just before retinal, a β-carotene consumption by BCM(D)O may be exactly proportional to the retinal productivity if there was retinal degradation. β-carotene remained in a culture solution of  Escherichia coli  including BCM(D)O other than SR, therefore, β-carotene cleavage activity of SR was expected to be the highest level among tested BCM(D)O. Accordingly, in an additional experiment, SR enzyme was adopted for retinal production. The cell growth did not come under the influence of over-expression of BCM(D)O gene except for  N. pharaonis  brp gene exhibiting delayed cell growth. 
     EXAMPLE 3 
     Gene Manipulation into MEP and MVA Paths for Supplying a Building Block 
     Retinal building blocks, that is, IPP and DMAPP may be synthesized in  Escherichia coli  through an inherent MEP path and a foreign MVA path ( FIG. 1 ). 
     It was reported that synthesis of 1-deoxy-d-xylolose-5-phosphate (DXP) is an important velocity restriction process in the MEP path. Therefore, over-expression of DXP synthase (to be encoded by dxs) increased production of lycopene and β-carotene in previous inventions of the present inventors. By introducing dxs gene into before the MEP path among pT-HBSR, pT-DHBSR was prepared. 
       FIG. 4  illustrates production of retinal and β-carotene, and cell growth of  Escherichia coli  including pT-HB, pT-HBSR, pT-DHB and pT-DHBSR, as well as  Escherichia coli  including pT-DHB or pT-DHBSR together with pS-NA as an MVA path plasmid. More particularly, white and grey bars show numerical values at 24 hours and 48 hours, respectively. 
     As shown in  FIG. 4 , the retinal productivity of  Escherichia coli  pT-DHBSR was a little higher than that of  Escherichia coli  pT-DHB at 24 hours, while being substantially similar to the same at 48 hours. However, β-carotene production by  Escherichia coli  pT-DHB was increased by about 1.5 times due to over-expression of dxs, as compared to  Escherichia coli  pT-HB. It is known that a foreign MVA path in  Escherichia coli  considerably increases production of isoprenoid by providing sufficient amounts of IPP and DMAPP building blocks.  Escherichia coli  pT-DHBSR/pS-NA including an additional foreign MVA path have produced 8.7 mg/L of retinal for 48 hours, which is 4 times higher than the productivity of  Escherichia coli  pT-DHBSR. For an  Escherichia coli  strain including SR gene, β-carotene did not remain or slightly remained in the cell. This condition is presumed due to an effective cleavage reaction of β-carotene by SR. There was a considerable difference between an amount of β-carotene (a substrate) consumption and an amount of produced retinal (a product). This difference may be due to the presence of a cellular reaction to metabolize retinal in  Escherichia coli  as well as biological degradation of retinal. Accordingly, formation of an alternative retinoid derived from retinal by any enzyme in  Escherichia coli  may be under consideration. Since the retinal can be converted into retinol, retinoic acid and retinyl ester by cell-enzyme reaction ( FIG. 2 ), retinal derivatives contained in an  Escherichia coli  culture solution were subjected to analysis. The analysis results showed that retinal derivatives other than retinoic acid were formed. According to further experiments, production of retinal, retinol and retinyl acetate was determined. 
     EXAMPLE 4 
     Effects of  Escherichia coli  Strain, Culture Conditions and Carbon Source in Relation to Retinoid Production 
     (1) Strain 
     With regard to production of retinoid including retinal, retinol and retinyl acetate, effects of  Escherichia coli  strains were investigated. Five  Escherichia coli  strains including pT-DHBSR and pS-NA, that is, MG1655, DH5α, XL1-Blue, S17-1 and BL21 (DE3) were used to produce retinoid. Table 7 shows characteristics of six  Escherichia coli  strains including the foregoing five strains. 
     
       
         
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                   E. coli  strain 
                 Details 
               
               
                   
               
             
             
               
                 MG1655 
                 K12, wild type 
               
               
                 DH5α 
                 F − , φf80dlacZΔM15, Δ(lacZYA-argF)U169, 
               
               
                   
                 deoR, recA1endA1, hsdR17(r K   − m K   + ), 
               
               
                   
                 phoA, supE44, λ−, thi-1, gyrA96, relA1 
               
               
                 XL1-Blue 
                 hsdR17, supE44, recA1, endA1, gyrA46, thi, relA1, 
               
               
                   
                 lac/F′[proAB + , lacI q , lacZΔM15::Tn10(tet r )] 
               
               
                 S17-1 
                 recA pro hsdR RP4-2-Tc::Mu-Km::Tn7 
               
               
                 BL21 (DE3) 
                 F − , ompT, hsdS B (r B   − m B   − ), 
               
               
                   
                 gal(lcI857, ind1, Sam7, nin5, lacUV5-T7 gene1), 
               
               
                   
                 dcm(DE3) 
               
               
                 BW25113 
                 Δ(araD-araB)567, ΔlacZ4787(::rrnB-3), lambda − , rph-1, 
               
               
                   
                 Δ(rhaD-rhaB)568, hsdR514 
               
               
                   
               
             
          
         
       
     
       FIG. 5  illustrates retinoid production and cell growth of five  Escherichia coli  strains, respectively, of which each has pT-DHBSR and pS-NA. Culturing was conducted in a 2YT medium including 0.5% (w/v) of glycerol and 0.2% (w/v) of arabinose at 29° C. for 48 hours. Retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. Also, in case of cell growth, MG1655, DH5α, XL1-Blue, S17-1 and BL21 (DE3) are represented by ▪, ●, ▴, ▾ and ♦, respectively. 
     As shown in  FIG. 5 ,  Escherichia coli  DH5α has produced 40 mg/L, that is, the largest amount of retinoid at 36 hours, and  Escherichia coli  S17-1 and XL1-Blue have produced about 22 mg/L, that is, the second largest amount of retinoid. However, from  Escherichia coli  MG1655 and BL21 (DE3), only a trace amount of retinoid was produced. Therefore,  Escherichia coli  DH5α was adopted as a strain for retinoid production. 
     (2) Culture Conditions 
     With regard to production of retinoid, effects of dissolved oxygen were investigated with difference test volumes in a test tube having a diameter of 30 mm. 
       FIG. 6  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on test volume. Referring to  FIG. 6 , retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. Also, in case of cell growth, test volumes of 3 mL, 5 mL, 7 mL and 10 mL are represented by ▪, ▪, ▴ and ▾, respectively. Culturing was conducted in a 2YT medium including 0.5% (w/v) of glycerol and 0.2% (w/v) of arabinose at 29° C. for 48 hours. 
     As shown in  FIG. 6 , it was found that retinoid production more early reached the maximum level at a small test volume (corresponding to highly dissolved oxygen), and the production was deemed to more quickly decrease due to oxidative degradation. With 10 mL of test volume, both of cell growth and retinoid production were delayed, while degradation of the product was observed by a small extent. It was found that the optimum test volume for retinoid production is 7 mL. 
     Further, the retinoid production depending upon the temperature was investigated.  FIG. 7  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on a culture temperature. Referring to  FIG. 7 , retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. Also, in case of cell growth, culture temperatures of 29° C., 34° C. and 37° C. are represented by ▪, ● and, respectively. Culturing was conducted in a 2YT medium including 0.5% (w/v) of glycerol and 0.2% (w/v) of arabinose at 29° C., 34° C. and 37° C., respectively, for 48 hours. 
     As shown in  FIG. 7 , the retinoid production has come under an influence of culture temperature and the highest production was accomplished at 29° C. 
     (3) Carbon Source 
     Effects of different carbon sources upon production of retinoid were compared. 
       FIG. 8  illustrates retinoid production and cell growth of  Escherichia coli  including pT-DHBSR and pS-NA depending on the carbon source. Referring to  FIG. 8 , retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. Also, in case of cell growth, no carbon source, and the carbon sources of glycerol, glucose, xylose, maltose and galactose are represented by ▪, ●, ▴, ▾, ♦ and, respectively. Culturing was conducted in a 2YT medium including 0.2% (w/v) of arabinose and 0.5% (w/v) of glycerol, glucose, xylose, maltose or galactose, at 29° C. for 48 hours. 
     As shown in  FIG. 8 , it was found that glycerol was the best carbon source for retinoid production. When glucose or galactose was used as the carbon source, the retinoid productivity was lower than that in case where the carbon source was not used. 
     Next, effects of a concentration of glycerol upon the retinoid production and cell growth were investigated.  Escherichia coli  DH5α(pT-DHBSR/pSNA) was grown in a 2YT medium including glycerol in a range of 0.0% to 2.0% (w/v), at 29° C. 
       FIG. 9  illustrates production of retinoids (retinal, retinol and retinyl acetate) of  Escherichia coli  including pT-DHBSR and pS-NA. Retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. 
       FIG. 10  illustrates cell growth of  Escherichia coli  including pT-DHBSR and pS-NA. Given glycerol concentrations of 0%, 0.5%, 1% and 2% are represented by ▪, ●, ▴ and ▾, respectively. 
     As shown in  FIGS. 9 and 10 , the cell growth was proportional to the glycerol concentration and increased. With the glycerol concentration of 0.5, 1.0 and 2.0% (w/v), the cell growth has become stagnate at 36, 48 and 72 hours, respectively. At the above time, the maximum retinoid productivity was accomplished and, thereafter, the productivity was considerably reduced during stagnation. It can be seen that the retinoid production generally increases after 24 hours. The retinoid productivity was about 95 mg/L, the highest level, at 2.0% (w/v) of glycerol among various glycerol concentrations, which is substantially 2.4 times higher than the maximum retinoid productivity at 0.5% (w/v) of glycerol. An increase in glycerol concentration delayed the stagnation while extending a period of retinoid production. 
     From all culture solutions, it was observed that the retinoid production was extremely reduced during stagnation of the cell growth, and this condition is deemed to be caused by discontinued production of retinoid during stagnation and intracellular oxidative degradation of the same. 
     (4) Culture in the Presence of Dodecane 
     Strains containing transformed pT-DHBSR/pSNA were used for six strains listed in Table 7. After adding 1 mL of dodecane to 5 ml of medium, culturing was conducted according to such conditions as described in “bacteria strain and culture conditions.” The medium used herein was a 2YT medium including 0.2% (w/v) of arabinose and 0.5% (w/v) of glycerol added thereto. 
       FIG. 11  illustrates results of the retinoid production depending on different  Escherichia coli  strains for retinoid production. As shown in  FIG. 11 , DH5α and MG1655 showed the largest amount of retinoid production. For MG1655, the cell growth and retinoid productivity were increased, as compared to no addition of dodecane. A cell growth rate and a rate of increasing retinoid productivity for MG1655 were obviously faster than DH5α. BL21 (DE3) strain showed a still high cell growth but had scarcely any production of retinyl acetate. Consequently, it was determined that DH5α and MG1655 among six strains are relatively suitable, as compared to other strains. 
       FIG. 12  illustrates results of growth of strains for retinoid production in the presence of dodecane. 
       FIG. 13  illustrates results of retinoid production and growth in the presence of dodecane, depending on the concentration of glycerol as a carbon source. 
     EXAMPLE 5 
     2-Phase Culture Using Dodecane for In-Situ Extraction of Retinoid 
     In order to prevent intracellular degradation of retinoid, a 2-phase culture method was conducted using a hydrophobic solvent, that is, dodecane, in order to perform in-situ extraction of retinoid from cells. Dodecane was selected since it has a low toxicity to  Escherichia coli  I, a high hydrophobicity (log P o/w , 6.6) for extracting hydrophobic retinoid, and low volatile properties not to cause evaporation loss. 
     In the present example, 1 mL of dodecane was added to 5 ml of culture solution.  FIG. 13  illustrates retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) in a 2-phase culture system including 1 mL of dodecane in 5 ml of culture medium. With regard to retinoid production, retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. In the case of cell growth, given glycerol concentrations of 0.5%, 1% and 2% are represented by ▪, ● and ▴, respectively. 
     Retinoid was extracted into the dodecane phase while an insignificant amount of retinoid was detected in the culture solution and cell mass (data not shown). As a result, the retinoid productivity was measured from the dodecane phase. As shown in  FIG. 13 , in-situ extraction could minimize intracellular degradation of retinoid by dodecane. The retinoid among the dodecane phase was deemed to be relatively stable and remained without significant oxidative degradation thereof. As comparing with the results shown in  FIGS. 9 and 10  (without addition of dodecane), the retinoid production was remarkably increased even at 24 hours in case of adding the dodecane. Further, the cell growth did not come under an influence of the dodecane addition while the retinoid production was not decreased during stagnation. However, in the culture using 2% (w/v) glycerol, the retinoid production was not so higher than that in case of using 1% (w/v) glycerol, even though the cell growth was remarkably increased in proportion to an increase in glycerol concentration from 1% (w/v) to 2% (w/v). When the volume of dodecane addition is 1 mL, it is insufficient to conduct effective in-situ extraction of retinoid in the culture using 2% (w/v) of glycerol. 
     In order to investigate effects of the volume of dodecane addition on the retinoid production and cell growth, 1 mL to 5 mL of dodecane was initially added to a culture solution including 2% (w/v) of glycerol ( FIG. 14 ). 
       FIG. 14  illustrates retinoid production and cell growth of  Escherichia coli  (pT-DHBSR/pS-NA) in a 2-phase culture system, depending on the volume of dodecane. With regard to the retinoid production, retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. In case of cell growth, volumes of overlaying dodecane of 0 mL, 1 mL, 2 mL, 3 mL, 4 mL, 5 mL and 6 mL are represented by ▪, ●, ▴, □, ∘, Δ and ⋆, respectively. 
       FIG. 15  illustrates a distribution of retinoid depending on culturing time and volume of dodecane, in terms of percentages of individual constituents to total retinoid. Retinal, retinol and retinyl acetate are represented by bright grey, dark grey and black colors, respectively. 
     As shown in  FIGS. 14 and 15 , production of overall retinoids was improved according to an increase in the volume of dodecane addition. In 72 hours culture using 5 mL of dodecane, the highest retinoid productivity of 136 mg/L was obtained, which is about 2 times higher value than that (65 mg/L) in case where 1 mL of dodecane is used. Meanwhile, in 72 hours-extended culture using 5 mL of dodecane, the retinoid productivity did not further increase but the highest level was maintained without degradation of the retinoid (data not shown). By adding 2 mL of dodecane to the culture solution at 0, 24 and 48 hours, a whole volume of dodecane addition was increased to 6 mL. In the culture using 6 mL of added dodecane, the total retinoid productivity did not increase, as compared to the culture using 5 mL of dodecane. Likewise, even in the culture using 6 mL of initially added dodecane, the retinoid productivity did not increase (data not shown). The cell growth in all of culture solutions including dodecane was slightly higher than that in case of not using dodecane ( FIG. 14 ). 
       FIG. 15  illustrates a distribution of produced retinoids depending on the volume of dodecane addition. With regard to ratios of obtained retinal and retinol, there is a considerable difference in retinoid distributions between addition of dodecane and no addition of dodecane. A ratio of retinal in retinoid at 48 hours was about 51% (w/v) in the dodecane-added culture and 23% (w/v) in the culture without adding dodecane. Likewise, a ratio of retinol ranged from 30 to 39% in the dodecane-added culture and was 59% in the culture without adding dodecane. Accordingly, the addition of dodecane may increase a ratio of retinal while reducing a ratio of retinol. In consideration of the order of reactions for formation of retinol from retinal in a cell, retinal is deemed to be extracted from the cell before conversion of the same into retinol by dodecane. Further, a ratio of retinyl acetate at 48 hours was less than 20% in both of the cultures with and without addition of dodecane, which is relatively lower than the ratios of retinal and retinol. In the culture with addition of dodecane, the ratio of retinyl acetate is reduced as the culturing time is extended and this indicates that activity of cells for forming retinyl acetate is reduced during culturing. Consequently, adding dodecane has prevented a decrease of retinoid production during stagnation of the cell growth, while improving the retinoid production. 
     The in-situ extraction of retinoid according to the present invention does not need lysozyme used for degrading a cell wall. Retinoid (C20, isoprenoid molecule) may be efficiently released from the cell without loss of the cell wall. In 2-phase culture for production of retinoid, β-carotene must be continuously maintained in the cell since it is a direct precursor of the retinoid. If β-carotene is extracted from the dodecane phase, it can be cut by BCD(M)O placed in cytosol. 
     Due to a size of molecule, β-carotene can neither be released from the cell nor extracted by dodecane, therefore, can be continuously maintained in the cell during 2-phase culture of β-carotene ( FIG. 16 ). 
       FIG. 16  illustrates effects of dodecane addition depending on β-carotene production and cell growth of  Escherichia coli  including pT-DHB and pS-NA. Culturing was conducted in 5 ml of 2YT medium including 0.5% (w/v) of glycerol and 0.2% (w/v) of arabinose at 29° C. for 48 hours while adding 1 mL of dodecane to the medium. Grey and black bars indicated 24 hours and 48 hours, respectively. 
     As shown in  FIG. 16 , an insignificant amount of β-carotene was detected in the dodecane phase and a whole β-carotene has been almost retained in the cell. There was not a noticeable difference in β-carotene production and cell growth between cultures with and without addition of dodecane. 
     In the culture with addition of 5 mL of dodecane, a total 122 mg/L of retinoid productivity was attained at 48 hours. However, in the culture without addition of dodecane, only half of the above productivity (60 mg/L) was obtained at the same time period. Accordingly, the dodecane-added 2-phase culture system may be appropriately applied to an alternative transformation system to produce small lipophilic molecules. 
     EXAMPLE 6 
     Production of Retinoid in Medium Including Lipophilic Substance 
     The present example was performed to identify as to whether a variety of lipophilic substances have effects of increasing retinoid production. 
     (1) Production of Retinoid in Medium Including Alkane 
     A strain DH5α including transformed pT-DHBSR/pSNA (DH5α(pT-DHBSR/pSNA)) was used, and after adding 5 mL of each of octane, decane, dodecane and tetradecane to 5 ml of medium, culturing was conducted according to such conditions as described in “Bacteria strain and culture conditions.” The medium used herein was a 2YT medium including 0.2% (w/v) of arabinose and 2.0% (w/v) of glycerol added thereto. 
       FIG. 17  illustrates results of retinoid production in the presence of alkane.  FIG. 18  illustrates results of growth of the retinoid producing strain in the presence of alkane. 
     As shown in  FIG. 17 , a total 108 mg/L of retinoid was produced in case of using decane. Alternatively, bacterial cell proliferation, pH and an amount of β-carotene in the bacterial cell did not show a considerable difference depending upon the presence of alkanes. Therefore, it is considered that decane may be more advantageous in retinoid production, as compared to dodecane. When using octane, production of retinal and retinol was similar to other alkanes, whereas retinyl acetate was almost not produced. Tetradecane showed a lower productivity of whole retinoids, as compared to other alkanes. 
     (2) Production of Retinoid in Medium Including Mineral Oil 
     (2.1) Lightweight Mineral Oil 
     The lightweight mineral oil is cheap and has an economical advantage, as compared to alkanes. A strain DH5α including transformed pT-DHBSR/pSNA (DH5α(pT-DHBSR/pSNA)) was used, and after adding the lightweight mineral oil in different volumes to 5 ml of medium, respectively, culturing was conducted according to such conditions as described in “Bacteria strain and culture conditions.” The medium used herein was a 2YT medium including 0.2% (w/v) of arabinose and 2.0% (w/v) of glycerol added thereto. 
       FIG. 19  illustrates results of retinoid production in the presence of lightweight mineral oil.  FIG. 20  illustrates results of strain growth in the presence of lightweight mineral oil. 
     As shown in  FIG. 19 , 158 mg/L of retinoid was produced in the presence of the lightweight mineral oil in an amount of 2 ml, as compared to 136.1 mg/L of retinoid produced using 5 mL of dodecane. As shown in  FIG. 20 , pH was not considerably different other than the case of using dodecane. On the other hand, bacterial cell growth was reduced as an amount of the lightweight mineral oil increased. The reason of this condition was deemed because the medium and mineral oil were not sufficiently admixed due to a high viscosity and specific gravity of the lightweight mineral oil. Owing to a decrease in growth of the bacterial cell, the retinoid production was also reduced. 
       FIG. 21  illustrates cell specific retinoids productivity. As shown in  FIG. 21 , a specific productivity of about 5 mg/L/OD 600  nm was observed regardless of an amount of mineral oil. 
     (2.2) Heavy Mineral Oil 
     The heavy mineral oil is cheaper than the lightweight mineral oil. A strain DH5α including transformed pT-DHBSR/pSNA (DH5α(pT-DHBSR/pSNA)) was used, and after adding 2 ml of heavy mineral oil to 5 ml of medium, culturing was conducted according to such conditions as described in “Bacteria strain and culture conditions.” The medium used herein was a 2YT medium including 0.2% (w/v) of arabinose and 2.0% (w/v) of glycerol added thereto. 
       FIG. 22  illustrates results of retinoid production in the presence of heavy mineral oil.  FIG. 23  illustrates results of strain growth in the presence of heavy mineral oil. As shown in  FIGS. 22 and 23 , the heavy mineral oil involved lower cell growth, as compared to the lightweight mineral oil and dodecane. Further, 104.6 mg/L of retinoid was produced. The reason of this condition was deemed because the medium and mineral oil were not sufficiently admixed due to a viscosity of the heavy mineral oil. 
     Except that a test tube was tilted and mounted on an incubator, cell culture was performed by the same procedures as described above. By tilting the test tube, effects of agitation were improved to thus allow the medium and mineral oil to be admixed more effectively. 
       FIG. 24  illustrates results of retinoid production when the culturing was conducted in a tilted test tube.  FIG. 25  illustrates results of strain growth when the culturing was conducted in the tilted test tube. As shown in  FIGS. 24 and 25 , the cell growth and retinoid production were increased when the culturing was conducted in the tilted test tube. More particularly, the retinoid was produced in an amount of 88.2 mg/L at 96 hours in a vertically-mounted test tube, while the retinoid productivity reached 173.9 mg/L in the tilted test tube. 
     The above results indicated that mixing the lightweight and/or heavy mineral oils with the medium is an important factor in retinoid production since the mineral oils have a high viscosity. Accordingly, the foregoing lightweight and/or heavy mineral oils may be used for retinoid by properly agitating the same during culturing. 
     (3) Production of Retinoid in Medium Including Skin-Friendly Lipophilic Substance 
     Retinoid was produced in a medium including a skin-friendly lipophilic substance. As the skin-friendly lipophilic substance, isopropyl myristate (IPM), dioctanoyl-decanoyl glycerol (ODO), cetyl ethylhexanoate (CEH) and phytosqualane were used. 
     A strain DH5α including transformed pT-DHBSR/pSNA (DH5α(pT-DHBSR/pSNA)) was used, and after adding 2 ml of heavy mineral oil to 5 ml of medium, culturing was conducted according to such conditions as described in “Bacteria strain and culture conditions.” The medium used herein was a 2YT medium including 0.2% (w/v) of arabinose and 2.0% (w/v) of glycerol added thereto. A control was prepared by adding 5 mL of dodecane to the medium. 
       FIG. 26  illustrates cell growth and pH in the presence of skin-friendly lipophilic substance.  FIGS. 27 and 28  illustrate results of retinoid production depending on an amount of skin-friendly lipophilic substance. As shown in  FIGS. 27 and 28 , in case of lipophilic substances other than dodecane, using 2 ml of lipophilic substance has achieved an increase in retinoid productivity, as compared to 5 ml of the same. In other words, when 2 ml of lipophilic substance was added to 5 ml of medium including the lightweight mineral oil, IPM, ODO, CEH and phytosqualane, large amount of retinoid was produced. Especially, when using IPM among IPM, ODO, CEH and phytosqualane, the largest amount of retinoid was produced. More specifically, when adding 2 ml of IPM, 180 mg/L of retinoid was produced. For IPM, in consideration of similar growth of bacterial cell, it is presumed to have a high specific productivity per bacterial cell.