Enzymatic Synthesis of Ethyl Butyrate in Supercritical Carbon Dioxide Using Surface Coated Lipase from Candida rugosa

The synthesis of low molecular weight ester, ethyl butyrate (used as a fruity flavor) by green chemistry is of immense importance to the food industry. Experiments were performed using Surface Coated Lipase (SCL) from Candida rugosa in supercritical carbon dioxide. The stability of enzyme in supercritical CO2 environment was validated and the influence of pressurization and depressurization on stability of enzyme was also studied. No significant loss of enzyme was noticed during pressurization and depressurization conditions even after 10 cycles. Further, experiments were performed to understand the effect of incubation time, temperature, enzyme concentration, reaction pressure on ester formation. The formation of ester gradually increased with incubation time. However, a steep increase in ester formation has been noticed between 7 and 10 h of incubation time. The reaction temperature appeared to have a profound effect on the product formation. The percent esterification increased linearly with increase in temperature and reached a maximum value of 92 % at 40°C and then decreased beyond this temperature. The percent esterification increased with the increase in enzyme concentration. The maximum percentage esterification of 92 % was observed at higher enzyme concentration [25 % w/w]. Reaction pressure seems to have marginal impact on the extent of alcoholysis and enzyme stability.