Optimization of carbohydrate fatty acid ester synthesis in organic media by a lipase from Candida antarctica

The effect of solvents and solvent mixtures on the synthesis of myristic acid esters of different carbohydrates with an immobilized lipase from C. antarctica was investigated. The rate of myristyl glucose synthesized by the enzyme was increased from 3.7 to 20.2 mu mol min(-1) g(-1) by changing the solvent from pure tert-butanol to a mixture of tert-butanol:pyridine (55:45 v/v), by increasing the temperature from 45 degreesC to 60 degreesC, and by optimizing the relative amounts of glucose, myristic acid, and the enzyme preparation. Addition of more than 2% DMSO to the tert-butanol:pyridine system resulted in a reduction of enzyme activity. Lowering the water content of the enzyme preparation below 0.85% (w/w) resulted in significant decreases in enzyme activity, while increasing the water content up to 2.17% (w/w) did not significantly affect the enzyme activity. The highest yields of myristyl glucose were obtained when an excess of unsolubilized glucose was present in the reaction system. In this case, all of the initially solubilized and a significant amount of the initially unsolubilized glucose was converted to the ester within 24 h of incubation, resulting in a myristyl glucose concentration of 34 mg/mL(-1). Myristic acid esters of fructose (22.3 mu mol min(-1) g(-1)), alpha -D-methylglucopyranoside (26.9 mu mol min(-1) g(-1)) and maltose (1.9 mu mol min(-1) g(-1)) could also be prepared using the tert-butanol:pyridine solvent system. No synthesis activity was observed with maltotriose, cellobiose, sucrose, and lactose as substrate. (C) 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 483-491, 2001.