Different performance of Escherichia coli mutants with defects in the phosphoenolpyruvate: carbohydrate...

In Escherichia coli, the transport and phosphorylation of glucose is mainly accomplished by the phosphoenolpyruvate-dependent glucose-specific phosphotransferase system (PTS^Glc), which is, therefore, frequently selected as a target for engineering to increase the intracellular level of phosphoenolpyruvate. Here we characterized the effects of a low glucose concentration on the growth, glucose consumption, and acetate secretion of individual strains with a single PTS^Glc mutation. We found that most mutants accumulated similar amounts of biomass, consumed glucose at lower rates, and secreted less acetate compared with the wild-type parental strain. The exception was the growth-impaired strain MG1655I harboring a ptsI deletion. In summary, the fermentation performance of mutant strains under 5 g/L glucose was obviously different with those strains under 20 g/L glucose. This study is a good complement to the knowledge of PTS^Glc in E. coli and indicates that engineering the components of PTS^Glc should be carefully optimized, particularly during fermentation in the presence of low concentrations of glucose.