Lipase-catalysed biosynthesis of hexyl butyrate by direct esterification: optimisation by response surface methodology

The ability of immobilised lipase from Rhizomucor miehei (Lipozyme IM-77) to catalyse the direct esterification of hexanol and butyric acid was investigated. Response surface methodology (RSM) and a four-factor/five-level central composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters such as reaction time (2-10 h), temperature (25-65 °C), substrate molar ratio of hexanol to butyric acid (1:1-3:1) and enzyme amount (10-50%; 0.24-1.18 BAUN) on the percentage molar conversion of hexyl butyrate by direct esterification. All the parameters had significant effects on the percentage molar conversion. Based on ridge maximum analysis, the optimal conditions for synthesis were: reaction time 8.0 h, temperature 46.9 °C, substrate molar ratio 1:1.2 and enzyme amount 36.4% (0.87 BAUN). The predicted value was 100% and the actual experimental value 98.2% molar conversion