beta-Galactooligosaccharide synthesis with beta-galactosidases from Sulfolobus solfataricus, Aspergillus oryzae, and Escherichia coli

The synthetic potential of the thermostable beta-glycosidase from Sulfolobu s solfataricus was compared with those of the commercially available, therm otolerant beta-galactosidase (beta-D)-galactoside galactohydrolase, EC 3.2. 1.23) from Aspergillus oryzae and the nonthermostable beta-galactosidase fr om Escherichia coli. To synthesize beta-galactooligosaccharides at differen t temperatures, the transglycosylation approach with lactose as donor and N -acetyllactosamine as acceptor was chosen as a model reaction. Generally, t he S. solfataricus enzyme gave the highest yields (48%), followed by the A. oryzae (36%) and the E. coli beta-galactosidases (32%). The main products obtained with the thermostable beta-glycosidase from S. solfataricus were b eta-D-Gal-[1-6]-D-GlcNAc, beta-D-Gal-[1-4]-D-GlcNAc and several oligosaccha rides. The enzyme from A. oryzae gave a similar product pattern but lower y ields. beta-D-Gal-[1-6]-D-GlcNAc was formed as the main disaccharide by the E. coli beta-galactosidase, and other products could only be detected in t race amounts. (C) 1999 Elsevier Science Inc. All rights reserved.