Activation of Alternative Respiration with Internal Electron Acceptor during Anaerobic Glucose Utilization in Escherichia coli Strains with Impaired Fermentation Ability

Abstract

The activation of alternative respiration with an internal electron acceptor during anaerobic glucose utilization in E. coli strains with impaired fermentation ability has been studied. It was found out that respiration processes utilizing pyruvic acid as an endogenous electron acceptor can markedly contribute to the maintenance of the anaerobic redox balance in E. coli strains deficient in mixed acid fermentation pathways. The sequential inactivation of the pathways of anaerobic dissimilation of pyruvate and impairment of the functionality of the reductive branch of the tricarboxylic acid cycle led to an increase in the contribution (from 11 to 54%) of the respiratory formation of lactic acid and alanine to the biosynthesis of the reduced products of anaerobic glucose utilization by the strains. Analysis of the enantiomeric composition of the lactic acid and alanine secreted by the strains demonstrated that D-lactate dehydrogenase (Dld), L-lactate dehydrogenase (LctD), and D-alanine dehydrogenase (DadA) participated in the biosynthesis of the respective compounds.