Characterization of a β-glucosidase with transgalactosylation capacity from the zygomycete Rhizomucor miehei

► A 82.293kDa β-glucosidase with thermo-acido-tolerant properties was characterized in Rhizomucor miehei. ► The enzyme is capable to synthesize oligosaccharides and alkyl-glucosides via transglucosylation. ► Transgalactosylation activity of the β-glucosidase was also proven. ► Liberation of phenolic antioxidants in sour cherry pomace could be enhanced by the purified enzyme. An extracellular β-glucosidase from the zygomycete Rhizomucor miehei NRRL 5282 cultivated in a wheat bran-based solid state fermentation system was characterized. The purified enzyme exhibited an optimum temperature of 68–70°C and pH of 5.0. It efficiently hydrolyzed oligosaccharides having β-(1→4) glycosidic linkages and exhibited some β- and α-galactosidase activity. The Vmax for p-nitrophenyl-β-d-glucopyranoside and cellobiose was 468.2 and 115.5U/mg, respectively, while the Km was 0.12mM for both substrates. The enzyme had transglucosylation and transgalactosylation activities resulting in the formation of glycosides from cellobiose, lactose and ethanol. The enzyme increased the amounts of free phenolic antioxidants in sour cherry pomace indicating that its hydrolyzing activity could potentially be applicable to improve the bioavailability of these compounds.