Yan_2002_Biotechnol.Bioeng_78_31

High conversions in lipase-catalyzed syntheses of esters from free acyl donors and an alcohol requires efficient removal of water preferentially at temperatures compatible to enzyme activity. Using a lipase B from Candida antarctica (CAL-B)-mediated synthesis of sugar fatty-acid esters, we show that a mixture of ethyl methylketone (EMK) and hexane (best ratio: 4:1, vo/vo) allows efficient removal of water generated during esterification. Azeotropic distillation of the solvent mixture (composition: 26% EMK, 55% hexane, 19% water) takes place at 59 degrees C, which closely matches the optimum temperature reported for CAL-B. Water is then removed from the azeotrope by membrane vapor permeation. In case of glucose stearate, 93% yield was achieved after 48 h using an equimolar ratio of glucose and stearic acid. CAL-B could be reused for seven reaction cycles, with 86% residual activity after 14 d total reaction time at 59 degrees C. A decrease in fatty-acid chain length as well as increasing temperatures (75 degrees C) resulted in lower conversions. In addition, immobilization of CAL-B on a magnetic polypropylene carrier (EP 100) facilitated separation of the biocatalyst.