Aspartic Acid Synthesis by Escherichia coli Strains with Deleted Fumarase Genes as Biocatalysts

Abstract

The work reports the construction of Escherichia coli strain MG1655 derivatives with deleted genes that encode fumarases (fumAC, fumB, and fumABC) via the phage lambda-mediated recombination system. It has been demonstrated that the deletion of fumB gene had almost no effect on strain growth under aerobic conditions, while the deletion of the fumA and fumC genes led to a 30% decrease in the growth rate under the same conditions. When the E. coli strains with deleted fumarase genes were used to catalyze L-aspartic acid synthesis from ammonium fumarate (1.5 M solution), it was observed that only the simultaneous loss of both the fumA and fumC genes led to an at least 20% increase in the aspartic acid yields and a concurrent decrease in the content of the byproduct malic acid in the reaction mixture from 40 to 1.5–2 g/L. The results obtained in the work may be used to generate more efficient novel biocatalysts of L-aspartic acid synthesis.