Water Activity Control in Organic Media by Equilibration Through Membranes
The catalytic activity of an enzyme in an organic medium depends on its hydration state. Of the different possible ways to quantify the amount of water present in the reaction mixture, the water activity has been shown to be preferable because it correlates well with the hydration state of the enzyme (compare Chapter 11). If other ways are used to quantify water in these systems, the results are often more difficult to interpret. In a typical example, the dependence of the enzymatic activity on the solvent was studied. The optimal water concentration varied within a wide range in the solvents studied, but the optimal water activity was virtually the same in all solvents (1). Similarly, the optimal water activity was the same when different support materials were used for immobilization of the enzyme but the optimal water concentration varied depending on the water-absorbing capacity of the support (2).
KeywordsWater Activity Silicone Tubing High Reaction Rate Salt Hydrate Saturated Salt Solution