Construction Of CBP Ethanologenic E. Coli Cells With Secreted β-glucosidase Expression

Recently, the production of clean energy from renewable resources has gained more attention because of the increasing depletion of fossil fuels and environmental concerns, and the because of the superior performance of fuel ethanol, bioethanol was regarded as the competitive potential alternative energy of oil, and the economical efficiency of cellulosic ethanol is the key to the industrialization.Study on constructing ethanologenic strain with cellulase secretory expression, to achieve the consolidated bioprocessing of degrading lignocellulose for ethanol production. In this study, we cloned the pyruvate decarboxylase gene pdc and alcohol dehydrogenase gene adhB from Zymomonas mobilis ZM4and then integrated the two genes into Escherichia coli JM109by Red recombination method to give a recombinant strain E. coli P81which was capable of ethanol generation from glucose. A beta-glucosidase gene bglB from Bacillus polymyxa1.794was secretively expressed in the recombinant E. coli P81to give a dual functional strain of cellobiose degradation and ethanol production, and named as E. coli P81(pUC19-bglB). The extracellular beta-glucosidase activity and the extracellular cellobiase activity of E. coli P81(pUC19-bglB) was determined as84.78mU/mL broth and32.32mU/mL broth, respectively. The recombinant strain E. coli P81(pUC19-bglB) fermented cellulose to produce ethanol and reached the yield55.8%of the theoretical yield, and when co-fermented glucose and cellobiose, the ethanol yield reached46.5%of thetheoretical yield. This E. coli strain provided a preliminary consolidated bioprocessing strain for converting cellobiose to bioethanol and a way for constructing a highly efficient and stable consolidated bioprocessing with secretive expression of cellulase enzymes.