Lipase-catalyzed production of a bioactive terpene ester in supercritical carbon dioxide.
Direct esterification of alpha-terpineol and acetic anhydride catalyzed by Candida rugosa lipase was performed in supercritical carbon dioxide (SC-CO(2)) with organic solvent serving as co-solvents. The highest yield of terpinyl acetate after 1.5h of reaction performance (95.1%) was obtained in SC-CO(2) with n-heptane serving as a co-solvent and immobilized Candida rugosa lipase as an enzyme at 50 degrees C. The optimal pressure for terpinyl acetate synthesis in SC-CO(2) medium was 10 MPa. Acetic anhydride was the best substrate among all acyl donors. Anhydrous enzyme was found to be the best for the esterification reaction. Lipase immobilization increased the catalytic efficiency up to 1.8-fold. The analysis of the initial rate data showed that reaction followed a Ping-Pong Bi-Bi mechanism with inhibition by acetic anhydride. The kinetic constants were obtained by multiple regression analysis of experimental findings. The reaction went smoothly without the use of hazardous reactants, and the developed method is useful for industrial application.