Optimized enzymatic synthesis of propylene glycol monolaurate by direct esterification

Propylene glycol monoesters with low hydrophile–lipophile balance value are widely used in the food industry. The ability of immobilized lipase, from Rhizomucor miehei (Lipozyme IM-77), to catalyze the direct esterification of propylene glycol with lauric acid was investigated in this study. Response surface methodology (RSM) and 3-level-4-factor fractional factorial design were adopted to evaluate the effects of synthesis variables, such as reaction time (3–9 h), temperature (25–65 °C), enzyme amount (15–45%) and substrate molar ratio of lauric acid to propylene glycol (1:1 to 3:1), on the percentage molar conversion to propylene glycol monolaurate. Results showed that reaction temperature and reaction time were the most important parameters and enzyme amount had less effect on percent molar conversion. Based on ridge max analysis, optimum synthesis conditions were: reaction time 7.6 h, temperature 37.6 °C, enzyme amount 37.1% and substrate molar ratio 2.6:1 with 100% molar conversion in this study. An actual experimental value of 96% molar conversion was obtained.