Enzymatic synthesis of symmetrical 1,3-diacylglycerols by direct esterification of glycerol in solvent-free system

1,3-Diacylglycerols were synthesized by direct esterification of glycerol w ith free fatty acids in a solvent-free system. Free fatty acids with relati vely low melting points (<45 degrees C) such as unsaturated and medium-chai n saturated fatty acids were used. With stoichiometric ratios of the reacta nts and water removal by evaporation at 3 mm Hg vacuum applied at 1 h and t hereafter, the maximal 1,3-diacylglycerol content in the reaction mixture w as: 84.6% for 1,3-dicaprylin, 84.4% For 1,3-dicaprin, 74.3% for 1,3-dilinol ein, 71.7% for 1,3-dieicosapentaenoin, 67.4% for 1,3-dilaurin, and 61.1% fo r 1,3-diolein. Some of the system's parameters (temperature, water removal, and molar ratio of the reactants) were optimized for the production of 1,3 -dicaprylin, and the maximal yield reached 98%. The product was used for th e chemical synthesis of 1,3-dicapryloyl-2-eicosapentaenoylglycerol. The yie ld after purification was 42%, and the purity of the triacylglycerol was 98 % (both 1,3-dicapryloyl-2-eicosapentaenoylglycerol and 1,2-dicapryloyl-3-ei cosapentaenoylglycerol included) by gas chromatographic analysis, of which 90% was the desired structured triacylglycerol (1,3-dicapryloyl-2-eicosapen taenoylglycerol) as determined by silver ion high-performance liquid chroma tographic analysis.