A comparison of the activities of three β-galactosidases in aqueous-organic solvent mixtures

The hydrolytic activities of β-galactosidases from three different sources have been determined in various 50% (v/v) organic solvent–buffer mixtures with a view to finding solvent systems of reduced water content suitable for the synthesis of glycosides and oligosaccharides. K. fragilis β-galactosidase lost activity rapidly (within 30 min) in all mixtures examined. The enzymes from E. coli and A. oryzae retained significant activity during extended periods (120 h) and are suitable for synthetic experiments. The level of activity depended on the enzyme and organic component of the solvent in the order tetraglyme > triethyl phosphate > monoglyme > triglyme = trimethyl phosphate > diglyme > diethylene glycol diethyl ether > 2-methoxyethyl acetate > acetone = acetonitrile (zero activity) for the E. coli enzyme and methoxyethyl acetate > trimethyl phosphate > triethyl phosphate > monoglyme > acetone ≈ diglyme ≈ triglyme ≈ tetraglyme > diethyleneglycol diethyl ether > acetonitrile for the A. oryzae enzyme.