Enzymatic preparation of oligosaccharides by transglycosylation: A comparative study of glucosidases

Abstract

Five glucosidases were studied with respect to their ability to catalyse the transglycosylation of maltose or cellobiose. Experiments were carried out at high substrate concentrations to increase the ratio between transglycosylation and hydrolysis. The properties of the enzymes were quite different, and as a simple descriptor of transglycosylation ability we suggest the use of the acceptor concentration (in this case, the disaccharide concentration) required to achieve the same initial rate in transglycosylation as in hydrolysis. We call this descriptor T50. Aspergillus niger transglucosidase had the lowest T50 value (30mM) and produced panose as the major product from maltose with a 69% yield after 6h. With a longer incubation time, secondary hydrolysis occurred and isomaltose could be obtained with a 65% yield. Aspergillus niger glucosidase was the most efficient enzyme for the transglycosylation of cellobiose with a T50 value of 130mM. It produced mainly cellotriose with the 1,6-linked trisaccharide (6-O-β-glucopyranosyl-cellobiose) as a side product. Almond β-glucosidase had a T50 value much higher than 320mM (the highest concentration tested), and it produced 6-O-β-glucopyranosyl-cellobiose as the main transglycosylation product.