Optimal formation of hexyl laurate by Lipozyme IM-77 in solvent-free system.

A medium-chain ester, hexyl laurate, with fruity flavor is primarily used in personal care formulations as an important emollient for cosmetic applications. To conform to the "natural" interests of consumers, the ability of immobilized lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyze the direct esterification of hexanol and lauric acid by using a solvent-free system was investigated in this study. Response surface methodology (RSM) and four-factor-five-level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (10-50 min), temperature (45-85 degrees C), lipase amount (10-30 mg/volume; 0.077-0.231 batch acidolysis units of Novo (BAUN), and pH memory (5-9), on percentage molar conversion of hexyl laurate by lipase-catalyzed direct esterification. Reaction time, temperature, and enzyme amount had significant effects on percent molar conversion. On the basis of ridge maximum analysis, the optimum synthesis conditions for hexyl laurate were a reaction time of 40.6 min, a temperature of 58.2 degrees C, an enzyme amount of 25.4 mg/volume (0.196 BAUN), and a pH memory of 5.9. The predicted percentage molar conversion of hexyl laurate was 69.7 +/- 1.4%.