Process for the transesterification of fat and oil

Abstract: A process for the transesterification of substrates comprising (a) fat and oil and (b) one or more compounds selected from the group consisting of fatty acid, fatty acid ester and other fat and oil with the use of a lipase, wherein said transesterification is effected in the presence of a monohydric lower alcohol.

Description: This invention relates to a process for the transesterification of fat and oil by using a lipase whereby a transesterified fat and oil of high qualities can be readily obtained. Conventional processes for the transesterification of fats comprise the use of various catalysts such as alkali metals and alkali matal alcoholates. However none of these processes shows a specificity of the site at which the transesterification occurs. Thus recently it has been attempted to effect site-specific transesterification by using a lipase. In order to effect transesterification by using a lipase as a catalyst, it is required to control the moisture content in the reaction system. When the moisture content in the reaction system is too low, the lipase can not be sufficiently activated and thus the aimed reaction can not be achieved. When the moisture content is excessively high, on the other hand, the fat is hydrolyzed, which causes, for example, a decrease in the yield of triglycerides or a deterioration of the obtained transesterified fat. Therefore transesterification with use of a lipase should be effected under strict control of the moisture content. However, water is hardly soluble in substrates or in an organic solvent and the range of the moisture content effective in the reaction is narrow which makes the control of the moisture content difficult. EP-A-126 416 discloses a method for transesterifying fats and oils by lipase involving the use of an alcohol having 4 to 18 carbon atoms, such as butanol. It is the object of the present invention to provide a process for the transesterification of fat and oil by using a lipase whereby a transesterified fat and oil of high quality can be readily obtained. This object of the present invention has been achieved by providing a process for the transesterification of substrates comprising (a) fat and oil and (b) one or more compounds selected from the group consisting of fatty acids, fatty acid esters and other fat and oil, by using a lipase, wherein said transesterification is effected in the presence of ethanol and the moisture content in the reaction system is from 0 to 0.18 % by weight based on the substrates. The fat and oil to be used in the present invention or other fat and oil to be transesterified therewith are not particularly restricted. Any edible animal and/or vegetable fat and oil commonly used may be employed. Examples thereof include palm oil, rapeseed oil, sunflower oil, safflower oil, shea fat, salt fat, chinese tallow, fish oil, beef tallow and lard which are optionally fractionated or hardened, They are used alone or as a mixture thereof. The fatty acids to be used in the present invention include saturated and/or unsaturated fatty acids having 8 to 22 carbon atoms which are normally found in the nature, such as palmitic acid, stearic acid, arachic acid, behenic acid, oleic acid and linoleic acid. The fatty acid esters to be used in the present invention include lower alcohol esters of the above fatty acids. Preferable examples thereof include esters of mono- or higher-hydric alcohols having 1 to 3 carbon atoms and the above fatty acids, such as glycerol monofatty acid esters, glycerol difatty acid esters, propylene glycol fatty acid esters and methyl oleate. The lipase to be used in the present invention is not particularly restricted. Any known one may be selected. The lipase may have a selectivity for, e.g., the substrate or site. A lipase which does not have any selectivity may also be employable. Examples of a lipase having a specificity at the 1,3-position of glyceride include those originating from microorganisms belonging to the genera Rhizopus , Mucor and Alcaligenes and pancreatic lipase. Examples of a lipase having no selectivity include those originating from microorganisms belonging to the genera Chromobacterium and Candida . Although these lipases may be used as such, it is preferable to immobilize same on a carrier such as Celite, an ion exchange resin or chitosan. Any carrier may be selected without limitation, long as it not inhibit the activity of the lipase. It is preferable to add the ethanol in an amount of at least 0.03 % by weight, more preferably 0.03 to 4.0 % by weight, still more preferably 0.1 to 4.0 % by weight and most preferably 0.1 to 2.0 % by weight, based on the substrates. An amount of ethanol of less than 0.03 % by weight causes a low transesterification ratio. On the other hand, when it exceeds the above range, undesirable hydrolysis might proceed. In the process of the present invention the moisture in the reaction system is minimized since it causes hydrolysis of the fat and oil to thereby accelerate the formation of side-products such as diglycerides, which lowers the yield of the triglycerides. The moisture content is from 0 to 0.18 % by weight, preferably from 0 to 0.15 % by weight, based on the substrates. However, it is expensive and requires complicated procedures to completely remove the moisture. Thus, from a practical viewpoint it is desirable to lower the moisture content to 0.01 to 0.15 % by weight, preferably to 0.02 to 0.1 % by weight. If necessary, an organic solvent such as hexane or acetone may be added to the reaction system. The temperature and period of the process of the present invention are appropriately selected depending on the aimed product and the enzyme to be used. Generally the reaction may be effected at a temperature of 20 to 80 °C. When the reaction is effected batchwise, the reaction period may range from 1 to 72 hours. When it is continuously effected, the reaction period may range from 1 minute to 1 hour. The transesterification process of the present invention is effected under the conditions as specified above and then the reaction product is purified by, for example, distillation. liquid/liquid extraction or solvent fractionation. Thus, the aimed transesterified fat and oil may be readily obtained. The present invention will further be illustrated by reference to the following examples, Example 1 To 30 g of palm oil medium fraction were added 24 g of stearic acid and 120 g of n-hexane. Then 0.3 % by weight. 0.6 % by weight, 1.2 % by weight and 2.0 % by weight, each based on the substrates, of ethanol were added thereto. Each mixture thus obtained was thoroughly dehydrated with Molecular Sieve 3A to thereby give a moisture content of 0.02 % by weight based on the substrate. Then 2 g of an immobilized lipase was added thereto and the resulting mixture was reacted at 40°C under stirring for 24 hours. The reaction product thus obtained was trimethylsilylated with use of hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMC)(manufactured by Wako Pure Chemical Industries. Ltd.) according to a process reported by J. Blum et al. (cf. Lipid, 5 , 601 (1970)) and the composition of the product was analyzed by gas chromatography. The immobilized lipase as described above was prepared according to a process described in Japanese Patent Laid-Open No. 213390/1984. Namely, 5. 15 g of Rhizopus dekenar lipase (manufactured by Seikagaku Kogyo K.K.) originating from Rhizopus ) was immobilized through adsorption on 100 g of a composite carrier comprising chitosan and Celite. For comparison, the same procedure as above was repeated except that no ethanol was added (moisture content based on the substrates: 0.02 % by weight) and that the ethanol was replaced with 0.2 % by weight of water, based on the substrates. Table 1 shows the results. Table 1 obviously indicates that the addition of ethanol elevates the efficiency of the transesterification. When ethanol was added, the triglyceride carrying 50 carbon atoms was decreased while those carrying 52 and 54 carbon atoms were increased, compared with the starting fat. In contrast thereto, when no ethanol was added, the reaction hardly proceeded. When no ethanol was added but 0.2 % by weight of water was added, the obtained product contained a large amount of diglycerides and had a poor quality. Example 2 One part by weight of palm oil, 0.8 part by weight of stearic acid and 4.5 parts by weight of hexane were thoroughly dehydrated with Molecular Sieve 3A. 0.01 part by weight of ethanol was added thereto. Each mixture thus obtained was fed into a column (0.9 cm (diameter) x 6 cm (height)) containing 2 g of an immobilized lipase at a flow rate of 18 ml/hr ad thus reacted at 45°C. The reaction product thus obtained was eluted stepwise by column chromatography (carrier: silica gel, developing solvent: n-hexane and n-hexane/ether = 70/30) to thereby collect the triglyceride fraction. A sample of this fraction was methylesterified to thereby determine the content of stearic acid incorporated into the triglycerides. The immobilized lipase used above was prepared by blending five parts by weight of Duolite S-587, one part by weight of Rhizopus delemar (disclosed in Japanese Patent Laid-Open No. 289884/1986) and ten parts by weight of a 0.1 M phosphate buffer solution (pH 7.0) . The resulting mixture was allowed to stand for ten hours and then dried. For comparison, the same procedure as above was repeated except that the ethanol was replaced with 0.15 % by weight of water, based on the substrates. Table 2 shows the results. Reaction period (day) Stearic acid contained in triglycerides produced (% by weight) Example Comp. Example ethanol water 1 38.9 36.8 4 38.6 33.5 10 37.7 30.5 The content of stearic acid in the starting oil was 4.2 % by weight. Example 3 The same procedure as in Example 1 was repeated except that the moisture content in the reaction system was adjusted to 0.1 % by weight based on the substrates and that the ethanol content was adjusted to 0.1 % by weight. 0.3 % by weight. 0.6 % by weight and 1.2 % by weight, each based on the substrates. For comparison, the same procedure as above was repeated except that no ethanol was added (moisture content: 0.1 % by weight based on the substrates). Table 3 shows the results. Example 4 One part by weight of sunflower oil and one part by weight of stearic acid were thoroughly dehydrated with Molecular Sieve 3A and then 0.01 part by weight of ethanol was added thereto. The resulting mixture was fed to columns (9 cm (diameter) x 18 cm (height)) each containing 3 g of LYPOZYM (manufactured by Novo Co., lipase originating from Mucor) at flow rates of 12 ml/h and 6 ml/h respectively and reacted at 69°C. Each product thus obtained was analyzed in the same manner as the one described in Example 2. For comparison, the same procedure as above was repeated except that the ethanol was replaced with an excessive amount of water, i.e., the substrates were saturated with water. Table 4 shows the results. Incorporated stearic acid (% by weight) 6 ml/h 12 ml/h Example 4 42.0 32.9 Comp. Ex. 39.1 27.2 The starting material contained 3.7 % by weight of stearic acid. Example 5 30 g of palm oil and 70 g of rapeseed oil were thoroughly dehydrated with Molecular Sieve 3A and then 1 g of ethanol and 3 g of an immobilized lipase were added thereto. The resulting mixture was extracted at 69°C for 24 hours under stirring. The above immobilized lipase was prepared In the same manner as the one described in Example 1. Namely, 3 g of a lipase originating from Candida cylindrasse (manufactured by Meito Sangyo Co., Ltd.) was immobilized through adsorption on 100 g of a composite carrier comprising chitosan and Celite. Then the triglyceride composition (% by weight) and SFC (solid fat content) were determined. The latter was determined according to a conventional method specified in American Oil Chemical Society Recommended Practice Cd16-18 Solid Fat Content with the use of PRAXIS MODEL SFC-900. Table 5 shows the results. Starting material Reaction product m.p. (°C) 26.4 15.7 Diglyceride content (% by weight) 3.0 6.0 Triglyceride content (% by weight) Carbon atom No. 46 0.7 0.5 48 3.7 2.7 50 14.1 10.5 52 20.9 34.2 54 52.3 46.6 56 3.8 3.3 58 1.4 1.4 60 0.4 0.3 SFC 1 °C 11.4 89 10 9.4 4.9 20 4.3 1.5 25 2.4 0.1 30 2.0 - 33 1.5 - 35 1.3 -

Claims: A process for the transesterification of substrates comprising (a) fat and oil, and (b) one or more compounds selected from the group consisting of fatty acids, fatty acid esters and other fat and oil by using a lipase, wherein said transesterification is effected in the presence of ethanol and the moisture content in the reaction system is from 0 to 0.18 % by weight based on the substrates. The transesterification process of claim 1, wherein the amount of ethanol is at least 0.03 % by weight based on the substrates. The transesterification process of claim 1, wherein the amount of ethanol is 0.03 to 4.0 % by weight based on the substrates. The transesterification process of claim 1, wherein the moisture content in the reaction system ranges from 0.01 to 0.15 % by weight based on the substrates.

Inventors: MATSUMOTO WATARU, NAKAI EIJI C O MR HAYAKAWA, NEZU TORU C O DORMITORY ICHIKA, SUZUKI KAZUAKI, MATSUMOTO, WATARU, NAKAI, EIJI C/O MR. HAYAKAWA, NEZU, TORU C/O DORMITORY ICHIKAWA, SUZUKI, KAZUAKI
Applicants: ASAHI DENKA KOGYO KK, ASAHI DENKA KOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: C12P7
IPC codes: C12P7, C11C3