Kinetic characterization in batch and continuous culture of Escherichia coli mutants affected in phosphoenolpyruvate metabolism: differences in acetic acid production

The growth kinetics of an Escherichia coli wild type strain and two derivat ive mutants were examined in batch cultures and in glucose-limited chemosta ts. One mutant (PB12) had an inactive phosphotranferase transport system an d the other (PB25) had interrupted pykA and pykF genes that code for the tw o pyruvate kinase isoenzymes. In both batch and continuous culture, importa nt differences in acetic acid accumulation and other metabolic activities w ere found. Compared to the wild type strain, we observed a reduction in ace tic acid accumulation of 25 and 80% in PB25 and PB12 strains respectively, in batch culture. Continuous culture experiments revealed that compared to the other two strains, PB25 accumulated less acetic acid as a function of d ilution rate. In continuous cultures, oxidoreductase metabolic activities w ere substantially affected in the two mutant strains. These changes in turn were reflected in different levels of biomass and CO2 production, and in o xygen consumption.