Improved activity of a bifunctional enzyme, tCel5A1-BglA, produced by fusion of a endoglucanase and a β-glucosidase

Abstract

The genes encoding the truncated version of Cel5A (tCel5A1) and β-glucosidase (BglA) from Thermotoga maritima were fused and expressed in E. coli BL21 CodonPlus (RIPL) cells to produce tCel5A1-BglA. This fusion enzyme was stable at 70 °C for 2 h. This bifunctional enzyme showed 1.3 and 2.6 fold increased activities on CMC and salicin, respectively, as compared to the individual endoglucanase and β-glucosidase enzymes. Similarly, a significant increase in activity was observed against the insoluble substrates, with 1.8, 1.8, 1.4, and 1.1 fold increase against wheat straw, rice straw, Avicel and RAC, respectively. Optimum pH for both endoglucanase and β-glucosidase activities of tCel5A1-BglA was found to be 6.0. Optimum temperature for endoglucanase and β-glucosidase activities was found to be 70 °C and 90 °C, respectively. Fusion of endoglucanase and β-glucosidase facilitates channeling of one enzyme’s product as substrate to the second enzyme thereby enhancing the overall biomass hydrolysis. Therefore, such fusion enzymes could be valuable for industrial applications.