DISACCHARIDE PRODUCTION BY GLUCOAMYLASE IN AQUEOUS ETHER MIXTURES

Five alpha-linked diglucosyl disaccharides (isomaltose, nigerose, kojibiose, maltose, and alpha,beta-trehalose) and two trisaccharides (isomaltotriose and panose) were produced in 90% aqueous solutions of 2-methoxyethyl ether, 2-ethoxyethyl ether, or triethylene glycol dimethyl ether by glucoamylase-catalyzed glucose condensation. Precipitation of the products and phase separation caused higher net production of disaccharides than expected by comparison with the same reactions occurring in solvent-free solutions. Glucoamylase was equally stable in water and in aqueous 90% 2-methoxyethyl ether, but was stabilized by further decreases of water concentration. Aqueous ethers neither modified the product specificity of glucoamylase nor changed the relative order of initial rates of disaccharide formation. Because of its broad specificity (five disaccharides and two trisaccharides), glucoamylase would not be a suitable biocatalyst for oligosaccharide synthesis.