Characterization of a recombinant β-glucosidase from the thermophilic bacterium Caldicellulosiruptor saccharolyticus

A recombinant β-glucosidase from Caldicellulosiruptor saccharolyticus DSM 8903 with a specific activity of 13 U/mg was purified by heat treatment and His-Trap affinity chromatography and identified as a single 54 kDa band on SDS-PAGE. The molecular mass of the native enzyme was 108 kDa as a dimer by gel filtration. β-Glucosidase showed optimum activity at pH 5.5 and 70 °C for p-nitrophenyl (pNP)-β-d-glucopyranoside. The half-lives of the enzyme at 60, 70, and 80 °C were 250, 24.3, and 0.4 h, respectively. The enzyme exhibited catalytic efficiency and specific activity for pNP-β-d-fucopyranoside, pNP-β-d-glucopyranoside, and pNP-β-d-galactopyranoside in decreasing order among aryl-β-glycosides, but not for aryl-α-glycosides. Cello-oligosaccharides from n = 2 to 5 as substrates using 4 mM each sugar and 3 U/mg of enzyme were completely hydrolyzed to glucose at 70 °C within 16 h.