Different performance of Escherichia coli mutants with defects in the phosphoenolpyruvate: carbohydrate phosphotransferase system under low glucose condition

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.