ANAEROBIC BIOSYNTHESIS OF INTERMEDIATES OF REDUCING BRANCH OF TRICARBOXYLIC ACIDS CYCLE BY Escherichia coli STRAIN WITH INACTIVATED frdAB AND sdhAB GENES

Abstract

GenesfrdAB and sdhAB encoding components of fumarate reductase and succinate dehydrogenase have been deleted in a recombinant E. coli strain with the inactivated pathways of mixed-acid fermentation and modified system of the glucose transport and phosphorylation at the heterological expression of the pyruvate carboxylase gene. Under anaerobic conditions, the parental strain effectively converted glucose into succinic acid without synthesizing significant amounts of fumaric or malic acid. When thefrdAB genes were individually deleted, the mutant strain was characterized by a low-efficient glucose fermentation with the formation of succinic acid along with secreting of considerable amounts of malic and succinic acids. The individual deletion of the sdhAB genes in the parental strain failed to have a visible effect on the effectiveness of the formation of the major product of fermentation. The combined inactivation of fumarate reductase and succinate dehydrogenase in the constructed strain enhanced the glucose anaerobic conversion into fumaric and malic acids during the activation of the glyoxylate by-pass and decreased contribution of the reducing branch of the TCA cycle to the formation of the target products.