Optimization of immobilized Candida rugosa lipase LIP2-catalyzed resolution to produce L-menthyl acetate

Esterification of L-menthol by lipase is a highly selective method for the resolution of DL-menthol. The present work focuses on the reaction parameters that affect lipase-catalyzed synthesis of L-menthyl acetate in n-hexane using triacetin as acyl donor. Genetically engineered LIP2, an isoform of Candida rugosa lipase, was used as a biocatalyst in the present study. The main objectives of the work were to develop an approach that would enable a better understanding of relationships between the variables (reaction time, temperature, enzyme amount, substrate molar ratio) and the response (molar conversion) for L-menthyl acetate synthesis, and to obtain the optimum conditions for synthesis. By using central composite rotatable design (CCRD) and response surface methodology (RSM) analysis, we found that substrate molar ratio and enzyme amount were the most important variables for the reaction. Based on ridge max analysis, the optimum synthesis conditions were found to be: reaction time 2.2 days, temperature 34.3 degrees C, enzyme amount 0.09 g and substrate molar ratio (DL-menthol:triacetin) 1:1.9, and molar conversion of DL-menthol to L-menthyl acetate was calculated to be 50%. An experiment under optimum conditions was carried out and molar conversion of 48.3% was obtained