Engineering Zymomonas mobilis for Robust Cellulosic Ethanol Production

Great effort has been devoted to engineering Saccharomyces cerevisiae with pentose metabolism through the oxido-reductase pathway for cellulosic ethanol production, but intrinsic cofactor imbalance is observed, which substantially compromises ethanol yield. Zymomonas mobilis not only can be engineered for pentose metabolism through the isomerase pathway without cofactor imbalance but also metabolizes sugar through the Entner-Doudoroff pathway with less ATP and biomass produced for more sugar to be used for ethanol production. Moreover, the availabilities of genome sequence information for multiple Z. mobilis strains and advanced genetics tools have laid a solid foundation for engineering this species, and the self-flocculation of the bacterial cells also presents significant advantages for bioprocess engineering. Here, we highlight some of recent advances in these aspects.