Discovery of two bifunctional/multifunctional cellulases by functional metagenomics

Cellulases are widely used in industry, and the usage in bioconversion of biofuels makes cellulases more valuable. In this study, two tandem genes that encoded cellulases ZF994–1 and ZF994–2, respectively, were identified on a cosmid from a soil metagenomic library. Phylogenetic analysis indicated that ZF994–1 and ZF994–2 belonged to glycoside hydrolase family 12 (GH12), and GH3, respectively. Based on the substrate specificity analysis, the recombinant ZF994–1 exhibited weak endoglucanase activity, moderate β-1,3-glucanase and β-1,4-mannanase activities, and strong β-glucosidase activity, while the recombinant ZF994–2 exhibited moderate endoglucanase activity and strong β-glucosidase activity. More than 45% β-glucosidase activity of the recombinant ZF994–1 retained in the buffer containing 3 M glucose, indicating the good tolerance against glucose. The recombinant ZF994–2 showed high activity in the presence of metal ions and organic reagents, exhibiting potential industrial applications.