Evaluation of anaerobic glucose utilization by Escherichia coli strains with impaired fermentation ability upon respiration with external and internal electron acceptor

Abstract

The characteristics of anaerobic glucose utilization and metabolite production by recombinant Escherichia coli strains with impaired fermentation ability upon respiration with pyruvate as an internal and nitrate as an external electron acceptor have been studied. It was found that respiration processes utilizing pyruvic acid as an endogenous electron acceptor and leading to the lactate and alanine formation were capable of mutual interference. After elimination of ammonium ions from the medium, the native activity levels of respiratory lactate dehydrogenases Did and LldD in E. coli strains deficient in the mixed acid fermentation pathways can almost completely compensate for the loss of activity of respiratory alanine dehydrogenase DadA, but are insufficient to maintain the entire intracellular redox balance. The addition of nitrate ions in the medium abolished alanine production by the strains despite the availability of ammonium ions, while the functionality of respiratory reduction of endogenous pyruvate to lactate retained in the studied strains even in the presence of a strong exogenous oxidant. Respiration with external electron acceptor provoked the activation of the oxidative tricarboxylic acid cycle in the strains. Anaerobic glucose utilization by the strain with interrupted tricarboxylic acid cycle increased during nitrate respiration, but remained restricted by the excessive generation of reducing equivalents in the residual reactions of the cycle. Escherichia coli, glucose, fermentation, respiration, pyruvate, lactate, alanine, nitrate, ammonium. The work was supported by a grant from the Russian Foundation for Basic Research (project #18-04-01222).