Characterization of a β-glucosidase Bgl17 from a metagenomics library of termite gut

Abstract:

[Objective] A novel β-glucosidase encoding gene bgl17, which was functional screened from a metagenomic library constructed from the gut of Globitermes brachycerastes, was expressed in Escherichia coli BL21 and its characteristic were studied. [Methods] The recombinant enzyme Bgl17 was purified, and the stability and kinetic were identified. And the hydrolysates were analyzed by thin layer chromatography. [Results] Bgl17 was belong to glycoside hydrolase family 1 (GH1), and the optimal temperature and pH of Bgl17 with p-nitrophenyl-β-D-glucopyranoside (pNPGlc) were 70 °C and 5.0, respectively. The specific activity of purified Bgl17 was 115.69 U/mg and 297.39 U/mg with pNPGlc and salicin as substrate, respectively. The Km and Vmax of Bgl17 were 0.81 mmol/L and 227.27 μmol/(mL·min) with pNPGlc, respectively. Bgl17 can remain 50% activity at 50 °C for 1 hour and 50% residual activity was detected after 1 h at pH 5.0 and 6.0. [Conclusion] The β-glucosidase Bgl17 showed the high activity with salicin, which might be beneficial to the degradation of lignocellulose. It showed the potential for industrial applications because of high thermostability. The optimal temperature of Bgl17 was much higher than that of termites’ living environment, which would contribute to the study of cellulose degradation mechanism of termites.

Key words:Globitermes brachycerastes gut, Metagenomic, β-Glucosidase, Glycosyl hydrolase family 1, Salicin