Synthesis of disaccharides using β-glucosidases from Aspergillus niger, A. awamori and Prunus dulcis

Glucose conversion into disaccharides was performed with β-glucosidases from Prunus dulcis (β-Pd), Aspergillus niger (β-An) and A. awamori (β-Aa), in reactions containing initial glucose of 700 and 900 g l^-1.

The reactions' time courses were followed regarding glucose and product concentrations. In all cases, there was a predominant formation of gentiobiose over cellobiose and also of oligosaccharides with a higher molecular mass. For reactions containing 700 g glucose l^-1, the final substrate conversions were 33, 38, and 23.5% for β-An, β-Aa, and β-Pd, respectively. The use of β-An yielded 103 g gentiobiose l^-1 (15.5% yield), which is the highest reported for a fungal β-glucosidase. The increase in glucose concentration to 900 g l^-1 resulted in a significant increase in disaccharide synthesis by β-Pd, reaching 128 g gentiobiose l^-1 (15% yield), while for β-An and β-Aa, there was a shift toward the synthesis of higher oligosaccharides.

β-Pd and the fungal β-An and β-Aa β-glucosidases present quite dissimilar kinetics and selective properties regarding the synthesis of disaccharides; while β-Pd showed the highest productivity for gentiobiose synthesis, β-An presented the highest specificity.