Cloning, expression and biochemical characterization of a GH1-glucosidase from Cellulosimicrobium cellulans

beta-Glucosidase plays an important role in the degradation of cellulose. In this study, a novel -glucosidase ccbgl1b gene for a glycosyl hydrolase (GH) family 1 enzyme was cloned from the genome of Cellulosimicrobium cellulans and expressed in Escherichia coli BL21 cells. The sequence contained an open reading frame of 1494bp, encoded a polypeptide of 497amino acid residues. The recombinant protein CcBgl1B was purified by Ni sepharose fastflow affinity chromatography and had a molecular weight of 57kDa, as judged by SDS-PAGE. The optimum -glucosidase activity was observed at 55 degrees C and pH 6.0. Recombinant CcBgl1B was found to be most active against aryl-glycosides p-nitrophenyl--D-glucopyranoside (pNPGlc), followed by p-nitrophenyl--D-galactopyranoside (pNPGal). Using disaccharides as substrates, the enzyme efficiently cleaved -linked glucosyl-disaccharides, including sophorose (-1,2-), laminaribiose (-1,3-) and cellobiose (-1,4-). In addition, a range of cello-oligosaccharides including cellotriose, cellotetraose and cellopentaose were hydrolysed by CcBgl1B to produce glucose. The interaction mode between the enzyme and the substrates driving the reaction was modelled using a molecular docking approach. Understanding how the GH1 enzyme CcBgl1B from C. cellulans works, particularly its activity against cello-oligosaccharides, would be potentially useful for biotechnological applications of cellulose degradation.