A Synthetic E. Coli Consortium for Efficient Conversion of Hexose and Pentose Monomers and Oligomers to Isobutanol

Complete and efficient co-fermentation of both hexose and pentose mono- and oligo-saccharides is one of the largest obstacles to cost-effective and scalable lignocellulosic biofuel production. To address this issue we have engineered a consortium of two isobutanol-producing E. coli strains which utilizes both hexose and pentose monosaccharides. Wild-type E. coli can serve as the hexose specialist due to its preference for hexose sugars, whereas the pentose specialist was created by deleting genes involved in hexose transport and assimilation. We then further engineered these strains to utilize oligomers, including cellobiose and xylodextrin, for maximum conversion of sugar mixtures generated from the enzymatic hydrolysis of cellulosic materials. Next, we investigate the growth characteristics and isobutanol production of this engineered consortium with minimal media containing various combinations of the sugars. In addition, we test the synthetic consortium on AFEX-pretreated corn stover hydrolysates in an effort to optimize isobutanol productivity on an industrially relevant feedstock.