Optimized synthesis of lipase-catalyzed hexyl acetate in n-hexane by response surface methodology

Abstract

Hexyl acetate, a short-chain ester with fruity odor, is a significant green note flavor compound and widely used in the food industry. The ability for immobilized lipase from Mucor miehei (Lipozyme IM-77) to catalyze the transesterification of hexanol with triacetin was investigated in this study. Response surface methodology and five-level-five-factor central composite rotatable design were adopted to evaluate the effects of synthesis variables, such as reaction time (2-10 h), temperature (25-65 degrees C), enzyme amount (10-50%; 0.024-0.118 BAUN), substrate molar ratio of triacetin to hexanol (1:1 to 3:1), and added water content (0-20%) on percentage molar conversion of hexyl acetate. The results showed that reaction temperature and substrate molar ratio were the most important parameters and that added water content had less of an effect on percent molar conversion. On the basis of canonical analysis, optimum synthesis conditions were as follows: reaction time, 7.7 h; temperature, 52.6 degrees C; enzyme amount, 37.1% (0.089 BAUN); substrate molar ratio, 2.7:1; and added water, 12.5%. The predicted value was 88.9% molar conversion, and the actual experimental value was 86.6% molar conversion.