Methods for Measurement and Control of Water in Nonaqueous Biocatalysis

Abstract

It is generally recognized that the small level of remaining water is critical to the behavior of biocatalysts used in mainly non-aqueous (e.g., organic) media. Most biocatalysts are inactive if fully dehydrated, and the reaction rate is stimulated by increasing hydration, at least at first. The rate of the desired reaction can become slower again if water levels increase too much, particularly when a hydrolytic side reaction becomes significant. The water level will also affect the equilibrium position of reactions in which it is a reactant. Most often, the desired synthesis will be the reversal of a hydrolysis or in competition with a hydrolytic side reaction. In such cases, the equilibrium yield will increase as the water level is reduced. Fuller details of these effects of water can be found in recent reviews of the field ( 1-7 ). Some further examples are found elsewhere in this volume (Chapters 12 and 13).