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

Objective 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 . Results 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. Conclusion 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.