Optimization of Enzymatically Prepared Hexyl Butyrate by Lipozyme IM-77

Hexyl butyrate, a green note flavour compound, is widely used in the food industry. The ability of immobilised lipase (Lipozyme IM-77) from Rhizomucor miehei to catalyse the transesterification of hexanol and tributyrin was investigated in this study. Response surface methodology (RSM) and five-level-five-factor central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction time (2 to 10 h), temperature (25 to 65 °C), enzyme amount (10 to 50 %), substrate amount (in mol) ratio of tributyrin to hexanol (1:1 to 3:1), and added water content (0 to 20 %), on percentage amount (in mol) conversion of hexyl butyrate by transesterification. Reaction time and enzyme amount were the most important variables and substrate amount (in mol) ratio had less effect on the percentage of amount (in mol) conversion. Based on canonical analysis, the optimum synthesis conditions were: reaction time 8.3 h, temperature 50 °C, enzyme amount 42.7 %, substrate amount (in mol) ratio 1.8:1, and added water 12.6 %. The predicted value was 96.2 % and actual experimental value 95.3 % of the amount (in mol) conversion.