Abstract
This minireview emphasizes the importance of control of trace amounts of moisture for biocatalytic reactions performed in organic solvents, no matter whether the solvent is water-soluble or water-immiscible, and whatever state of the biocatalyst is applied. The term ‘microaqueous’ is introduced to emphasize the importance of moisture control and to describe the reaction system precisely, for all possible biocatalytic forms in organic solvents. States of water molecules in the microaqueous organic solvents containing enzyme are discussed.