P151: Engineering of Escherichia coli for production of biobutanol from mixed sugars

Energy from renewable resources has aroused much interest in the academic society and industry. Lignocellulose is the most abundant material and decomposed to two dominant sugars, glucose and xylose. In Escherichia coli, xylose is not metabolized until glucose is used up. This pattern of sequential utilization of sugars makes the fermentation process based on E. coli ineffective. In this study, E. coli strain was manipulated by pathway engineering to co-utilize glucose and xylose. This was approached by deregulation of the catabolite repression. The carbon flux in the pentose phosphate pathway was then enhanced, and competing pathways were all removed. As a result, the engineered strain became able to co-assimilate glucose and xylose. To produce n-butanol, heterologous genes including phaA, hbd, crt, ter, and adhE2 genes were individually integrated into the E. coli genome, resulting in an E. coli producer strain. Fermentative production of n-butanol was then carried out with the shake-flask culture. With 20 g/L glucose, the E. coli producer strain was able to produce 3 g/L n-butanol within 24 h. Furthermore, there was 1.7 g/L n-butanol produced by the strain that was grown on 20 g/L xylose. In the presence of mixed sugars (10 g/L for each), the E. coli producer strain could simultaneously utilize glucose and xylose. After 24-h fermentation, both sugars were all consumed with n-butanol production reaching 2.2 g/L.