Biochemical property of an endo-glucanase-like enzyme from Clostridium sp. Z-7026

Clostridium sp. Z-7026 is a cellulose-degrading anaerobic bacterium, and its genome was recently sequenced. By Blast analysis against the NCBI protein database, one gene encoding a cellulase-like protein was identified. This deduced protein was named Cel_2759, and the Cel_2759 encoding gene was cloned, expressed in Escherichia coli, and purified. The purified recombinant protein had an estimated size of 107 kDa. To reveal its hydrolyzing ability, five substrates, namely carboxymethylcellulose (CMC), regenerate amorphous cellulose (RAC), crystalline cellulose Avicel beechwood xylan (BWX), and pretreated rice straw were used for activity assay. Results showed that, with in 15 min, Cel_2759 actively hydrolyzed CMC, yielding a reducing sugar concentration of 689.45 ?g/mL. However, activities against RAC, BWX and rice straw required pronged incubation time up to 16 h, yielding reducing sugar concentrations of 73.32 ?g/mL, 1393.05 ?g/mL, 875.704 ?g/mL, respectively. At 24 h, activity against Avicel was not observed, suggesting that Cel_2759 was unable to hydrolyze crystalline cellulose