beta-N-Acetylhexosaminidase from Aspergillus oryzae catalyzes the reverse glycosylation of N-acetylglucosamine (1.5 M) to GlcNAcp beta 1-->6GlcNAcp in 14% yield. Addition of salts [LiCl, (NH4)(2)SO4 0.1-1 M] lowers the water activity in the system thus increasing the yield of the thermodynamically controlled reaction. Benzylalcohol as acceptor gives under the same conditions benzyl O-beta-D-2-acetamido-2-deoxy-glucopyranoside.