KINETIC CHARACTERIZATION OF ESTERIFICATION CATALYZED BY RHIZOPUS-DELEMAR LIPASE IN LECITHIN-AOT MICROEMULSION SYSTEMS

The esterification of oleic acid with octyl alcohol catalyzed by Rhizo pus delemar lipase in microemulsion systems was investigated in terms of the kinetic parameters. The amphiphiles used were AOT and lecithin, both singly and as dual components. The enzyme activity in the lecith in system was high under hydrophobic conditions, i.e., at a W-L (= [H2 O]/[lecithin]) of 4.5, whereas in the AOT system it was high at W (= [ H2O]/[AOT]) = 7. The reaction kinetics were recognized to follow the p ing-pong bi-bi mechanism. A dual lecithin-AOT amphiphile system was ef fective in lipase The optimal molar fraction of lecithin for the maxim um initial reaction rate differed with the water concentration in the microemulsion phase. Under relatively hydrophobic conditions, i.e., in a system with a lower W-D (= [H2O]/[lecithin + AOT]), the initial rea ction rate had a higher maximum value. (C) 1998 Elsevier Science B.V.