| Summary: | Cellulase has been widely used in many industrial fields, such as feed and food industry, because it can hydrolyze cellulose to oligosaccharides with a lower degree of polymerization. Endo-β-1,4-glucanase is a critical speed-limiting cellulase in the saccharification process. In this study, endo-β-1,4-glucanase gene (<i>CelA257</i>) from <i>Myxococcus</i> sp. B6-1 was cloned and expressed in <i>Escherichia coli</i>. CelA257 contained carbohydrate-binding module (CBM) 4-9 and glycosyl hydrolase (GH) family 6 domain that shares 54.7% identity with endoglucanase from <i>Streptomyces halstedii</i>. The recombinant enzyme exhibited optimal activity at pH 6.5 and 50 °C and was stable over a broad pH (6–9.5) range and temperature < 50 °C. CelA257 exhibited broad substrate specificity to barley β-glucan, lichenin, CMC, chitosan, laminarin, avicel, and phosphoric acid swollen cellulose (PASC). CelA257 degraded both cellotetrose (G<sub>4</sub>) and cellppentaose (G<sub>5</sub>) to cellobiose (G<sub>2</sub>) and cellotriose (G<sub>3</sub>). Adding CelA257 increased the release of reducing sugars in crop straw powers, including wheat straw (0.18 mg/mL), rape straw (0.42 mg/mL), rice straw (0.16 mg/mL), peanut straw (0.16 mg/mL), and corn straw (0.61 mg/mL). This study provides a potential additive in biomass saccharification applications.
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