Transesterification Of Animal Oil Catalyzed By Lipase And Method Improving Lipase-Catalyzed Efficiency

The technology of lipase-catalyzed methanolysis and ethanolysis of lard and alkali-catalyzed methanolysis of lard was studied to produce fatty acid esters. Lipase activity and the catalytic efficiency can be affected by added reaction media, such as organic solvents, water content, metal ions, ion concentration and hydroxyl protecting agent in lipase-catalyzed transesterification of lard. The results are as follows.A higher conversion of lard methanolysis (or ethanolysis) was reached when3.45g lard was catalyzed by400mg lipase, at3:1molar ratio of methanol (or ethanol) to lard, three cycles of methanol (or ethanol) addition, at160r/min and38℃. The conversion of lard methanolysis was77.5%at72h under the optimal conditions. The conversion was60.8%when ethanolysis of lard was catalyzed by200mg lipase at96h under the optimal conditions. Ethanol is known to be a good material to lipase-catalyzed transesterification of lard. A higher conversion was reached at6:1molar ratio of methanol to lard,1%(w/w) sodium hydroxide, at160r/min and60℃for2.5h. The conversion was92.9%under the optimal conditions.By gas chromatography analysis, the products obtained by lipase-catalysis and alkali-catalysis included myristic acid methyl ester, palmitic acid methyl ester, palmitoleic acid methyl ester, stearic acid methyl ester, oleic acid methyl ester and linoleic acid methyl ester. The amount of methyl esters of long chain fatty acid were more by lipase-catalysis than by alkali-catalysis, and a small amount of capric acid methyl ester and lauric acid methyl ester were produced by lipase-catalyzed lard methanolysis. The amount of myristic acid methyl ester, palmitic acid methyl ester and palmitoleic acid methyl ester were more by alkali-catalysis than lipase-catalysis, and a small amount of lauric acid methyl ester was produced by lipase-catalysis lard methanolysis. There was no significant difference in the composition and content of methyl ester between lipase-catalyzed lard methanolysis and chemical-catalyzed lard complete methanolysis. The conversion was lower by glycerol determination than by gas chromatography determination.The reaction media affected greatly lipase activity and conversion in lipase-catalyzed transesterification of lard. The conversion increased by8.8%after20%(v/v) n-hexane was added in the reaction system in comparison with non n-hexane addition. In the reaction system containing40%n-hexane, the conversion increased by29.2%when20%(v/v) phosphate buffer (50mmol·L-1, pH6.8) was added than the control of water addition, the conversion increased by6.7%and6.5%by adding20%phosphate buffer solution and1mmol·L-1calcium and barium ion than the control, and the conversion increased by4.4%and6.25%by adding20%phosphate buffer solution and0.1mmol·L-1magnesium and zinc ion than the control. In the reaction system containing40%n-hexane and20%phosphate buffer solution, the conversion increased by1.9%,7.1%,6.9%and4.5%by adding0.05mmol·L-1glucose, trehalose, maltose and starch than the control, and the conversion increased by7.2%by adding1.83%(v/v) glycerol than the control.