EFFECTS OF WATER ACTIVITY ON REACTION-RATES AND EQUILIBRIUM POSITIONSIN ENZYMATIC ESTERIFICATIONS

A technique of continuous water activity control was used to examine t he effects of water activity on enzyme catalysis in organic media. Est erification catalyzed by Rhizopus arrhizus lipase was preferably carri ed out at a water activity of 0.33, which resulted in both maximal ini tial reaction rate and a high yield. When Pseudomonas lipase was used as catalyst it was beneficial to start the reaction at high water acti vity (giving the optimal reaction rate with this enzyme) and then shif t to a lower water activity toward the end of the reaction to obtain a high yield. The apparent equilibrium constant of the reaction was inf luenced by the water activity of the organic solvent. (C) 1994 John Wi ley and Sons, Inc.