Characterization of a GH family 3 β-glycoside hydrolase from Chrysosporium lucknowense and its application to the hydrolysis of β-glucan and xylan

Abstract

The Bxl5-gene encoding a GH3 glycoside hydrolase of Chrysosporium lucknowense C1 was successfully cloned, the homologous recombinant product was secreted, purified and characterized. Bxl5 (120 ± 5 kDa) was able to hydrolyze low molecular weight substrates and polysaccharides containing β-glucosidic as well as β-xylosidic residues. The K(m) and V(max)/E values were found to be 0.3mM and 88 s(-1) on p-nitrophenyl-β-d-glucopyranoside (PNPG), and 13.5mM and 1.8s(-1) on p-nitrophenyl-β-d-xylopyranoside (PNPX). Optimal pH and temperature for Bxl5 were 4.6 and 75°C for the PNPG hydrolysis, and 5.0-5.5 and 70°C for PNPX hydrolysis. The enzyme was quite stable when incubated at elevated temperatures up to 65°C. Bxl5 hydrolyzes polymeric β-glucans by the exo-mechanism allowing their complete conversion to d-glucose and is effective for xylan hydrolysis in combination with endo-acting xylan-degrading enzymes. The enzyme seems to be a very promising for bioconversion purposes.