Effect of water on methanolysis of glycerol trioleate catalyzed by immobilized lipase Candida sp. 99-125 in organic solvent system

摘要

In this study, hydrolysis and methanolysis of glycerol trioleate (TG) by lipase Candida sp. 99-125 were investigated under different water conditions. Both the reaction rates were relatively low without water, while increasing water content to 5 wt.% (or more, from 10-20%) based on the TG amount caused remarkable higher TG conversion for both reactions. Moreover, comparing the time course curves of the hydrolysis and methanolysis, it could be concluded that the methanolysis reaction catalyzed by this Candida sp. 99-125 appeared to accord with the successive reaction mechanism. TG was first hydrolyzed to partial glycerides and oleic acid (OA), then oleic acid methyl ester (OAME) was produced by esterification of the OA with methanol. This water effect was also confirmed by the experiments that water substitutions such as t-butanol and some surfactants added into the system did not get such high yields as that of the water included system. So these results showed that water took part in the methanolysis reaction, and successive hydrolysis-esterification process might be the catalytic mechanism of this lipase.