Expression of galactose permease and pyruvate carboxylase in Escherichia coli ptsG mutant increases the growth rate and succinate yield under anaerobic conditions.

In Escherichia coli, disruption of ptsG, which encodes the glucose-specific permease of the phosphotransferase transport system (PTS) protein EIICB(Glc), is crucial for high succinate production. This mutation can, however, cause very slow growth and low glucose consumption rates. The ptsG mutant (TUQ2), from wild type E. coli W1485, and E. coli galP (encoding galactose permease) and glk (encoding glucose kinase) gene expression plasmids were constructed. TUQ2 increased the generation time to approximately 4 h and gave a higher final cell density of 0.5 g/l by expression of galP. However, glk expression had no effect on the mutant. After expression of pyruvate carboxylase (PYC) and galactose permease, the ptsG mutant showed higher succinate yield (1.2 mol/mol glucose) and the specific rate of glucose consumption from 0.33 to 0.6 g/1 h.