Phenotypic changes in E. coli engineered for effective sugar utilization and its key factors involved in strain improvement

Abstract

Bioconversion of lignocellulosic biomass for complete and rapid assimilation is considered as an important alternative in cost effective cellulosic fuel production. Carbon catabolite repression leads to the limitation in various sugars utilization and decrease the potential of E.coli for efficient conversion. Towards this strategy, we have developed microbial hosts that confer cellobiose utilization phenotype by activating two endogenous cryptic operons through promoter engineering (CP12chbasc). Whole cell evolutionary mutation was performed in the above strain for 30 days to confer maximum utilization of cellobiose and co utilization of cellobiose and xylose phenotypes (CP12chbasc30). Capacity of engineered strains to grow on various sugars and co-utilization of the above sugar mixtures were also investigated. CP12chbasc30 strain also showed maximum utilization of cellobiose, xylose, galactose and mannose and exhibited YebK* phenotypes. Several evidences were addressed regarding yebK deleted strains with growth and expressions on various sugars and anaerobic condition. This indicated possibility of glyoxylate pathway and other reactions around TCA cycle could be controlled by YebK. These results would provide new insights for new strain improvement strategy.