| The ability of lipase from Candida rugosa to catalyze the resolution of (±)-menthol was investigated. Response surface methodology (RSM) and five–level–five–factor central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time, temperature, amount of lipase , substrate molar ratio of menthol to propionic anhydride, and water activity in reaction system on conversion of menthol and production enantiomeric excess. Reaction temperature, amount of lipase, substrate molar ration and reaction time were the most significant variables. Based on the analysis of RSM, the optimum resolution conditions were as follows: reaction time 10 h, temperature 27.52 ?C, amount of lipase 161.97 U/ml, substrate molar ratio 1:0.91, and water activity 0.14. The predicted value of conversion and enantiomeric excess were 53.84% and 84.78%, and the actual experimental values were 53.77% and 84.05, respectively.Immobilization of lipase from Candida rugosa was also investigated because of the difficulties in lipase recycle in ionic liquids with high viscosity. Superparamagnetic particles of 2～10μm were used as immobilization support both in directly covalent binding and in ion-exchange adsorption in buffers of different pH values after modified with DEAE. Optically active menthyl propionate of (-)-menthol was synthesized by enantioselective esterification of (±)-menthol in ionic liquid using immobilized CRL as a biocatalyst. Reaction parameters such as time, temperature, pH value and water content of immobilized lipase were studied. It showed that lipase immobilized in a buffer of pH 5.0 represented an extremely high enantioselectivity even compared with free lipase of over 90% enantiomeric excess after reacted for 24h. In a study of operation stability of immobilized and free lipase in ionic liquid, a comparable decrease of activity in both lipase forms was found while the former one remained its enantioselectivity of 70%.
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