11-20: Direct conversion of cellulosic biomass into ethanol using engineered recombinant Escherichia coli: Improvement of enzymatic accessibility toward substrate

Previously, we constructed the whole-cell biocatalyst, which displays all three different types of cellulases from Clostridium cellulolyticum on the surface of Escherichia coli, and demonstrated the efficiency of the hydrolysis rate and the production of ethanol from cellulosic biomass.  In this study, the enzymatic hydrolysis rate and ethanol productivity were evaluated after the synergism and accessibility of cellulases toward the substrate were improved.  Two extracellular endoglucanases, Cel9A and Cel9M, which are well known as efficient cellulosomal endoglucanases, were excreted into the media.  On the other hand, the beta-glucosidase and cellobiohydrolase, Cel9E, were surface displayed by fusing with the anchor protein PgsA.  The extracellular free cellobiohydrolase, Cel9E, was also constructed, and the substrate degradability and ethanol productivity were investigated.