Biochemical characterization of a novel thermo‐halo‐tolerant GH5 endoglucanase from a thermal spring metagenome

A novel endoglucanase gene, cel M , was cloned from a thermal spring metagenome. The gene was expressed in Escherichia coli , and the protein was extracted and purified. The protein catalyzed the hydrolysis of amorphous cellulose in a wide range of temperatures, 30–95°C, with optimal activity at 80°C. It was able to tolerate high temperature (80°C) with a half‐life of 8 h. Its activity was eminent in a wide pH range of 3.0–11.0, with the highest activity at pH 6.0. The enzyme was tested for halostability. Any significant loss was not recorded in the activity of Cel M after the exposure to salinity (3 M NaCl) for 30 days. Furthermore, Cel M displayed a substantial resistance toward metal ions, denaturant, reducing agent, organic solvent, and non‐ionic surfactants. The amorphous cellulose, treated with Cel M , was randomly cleaved, generating cello‐oligosaccharides of 2–5 degree of polymerization. Furthermore, Cel M was demonstrated to catalyze the hydrolysis of cellulose fraction in the delignified biomass samples, for example, sweet sorghum bagasse, rice straw, and corncob, into cello‐oligosaccharides. Given that Cel M is a thermo‐halo‐tolerant GH5 endoglucanase, with resistance to detergents and organic solvent, the biocatalyst could be of potential usefulness for a variety of industrial applications.