Optimal lipase-catalyzed formation of hexyl laurate

Abstract

A medium-chain ester, hexyl laurate, with a fruity flavor is primarily used in personal care formulations as an important emollient for cosmetic applications. In order to conform to the “natural” interests of consumers, the ability for immobilized lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyze the direct esterification of hexanol and lauric acid was investigated in this study. Response surface methodology (RSM) and 4-factor-5-level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (20 to 100 min), temperature (25 to 65 °C), enzyme amount (10 to 50%), and substrate molar ratio of hexanol to lauric acid (1 : 1 to 3 : 1) on percentage molar conversion of hexyl laurate by direct esterification. Reaction time and enzyme amount had significant effects on percent molar conversion. Based on ridge max analysis, the optimum conditions for synthesis were: reaction time 74.8 min, temperature 47.5 °C, enzyme amount 45.5%, and substrate molar ratio 1 : 1.5. The predicted value was 90.0% and the actual experimental value 92.2% molar conversion.