Methylation in methanol-water mixtures: the effect of solvent composition and high pressure

The effect of pressure (0.1 to 400 MPa) and solvent composition (methanol concentration of 5 to 30%) on the synthesis of beta-methylgalactoside was studied. Galactose was used as a reactant and the reaction was catalyzed by beta-galactosidase from Aspergillus oryzae. Under the applied conditions the enzyme was sufficiently stable and the reaction equilibrium was reached. Higher methanol concentrations obviously influenced the product yield positively due to an increase in reactant concentration but also due to a solvent effect. This solvent effect can be explained by measurement of the activities of galactose and methylgalactoside. These results may be generalized to other methylations in methanol-water systems, where methanol positively affects synthesis yields. Pressure had a small, negative effect on synthesis yields.