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

An extracellular beta-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 degrees C and pH of 5.0. It efficiently hydrolyzed oligosaccharides having beta-(1 -> 4) glycosidic linkages and exhibited some beta- and alpha-galactosidase activity. The V-max, for p-nitrophenyl-beta-d-glucopyranoside and cellobiose was 468.2 and 115.5 U/mg, respectively, while the K-m, was 0.12 mM 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. (C) 2012 Elsevier Ltd. All rights reserved.