Model-guided strain improvement: Simultaneous hydrolysis and co-fermentation of cellulosic sugars

The production of ethanol from starch or sugarcane-based substrates has been practiced at large scales for decades. Yet, despite tremendous effort, no economical production of ethanol from the abundant plant biomass in plant cell walls has been implemented. Two of the many outstanding problems in the cellulosic ethanol industry that must be resolved include the economic saccharification of recalcitrant plant cell walls and the efficient fermentation of mixed sugars (glucose and xylose) prevalent in cellulosic hydrolysates. In other words, the industry needs better celluloytic enzymes and better fermenting microbes to produce cellulosic ethanol. In this issue of Biotechnology Journal, a comprehensive model of cellulose hydrolysis and fermentation of prevalent sugars in lignocellulosic hydrolysates has been developed to evaluate the performance of cellulase enzymes and fermenting microbes in various ethanol production scenarios. This model will prove useful in guiding the engineering of cellulase enzymes and fermenting microbes for producing cellulosic ethanol economically.