Pyruvic Acid Production from Sucrose by Escherichia coli Pyruvate Dehydrogenase Variants

Abstract

Sucrose is an abundant, cheap, and renewable carbohydrate which makes it an attractive feedstock for the biotechnological production of chemicals. Escherichia coli W, one of the few safe E. coli strains able to metabolize sucrose, was examined for the production of pyruvate. The repressor for the csc regulon was deleted in E. coli W strains expressing a variant E1 component of the pyruvate dehydrogenase complex, and these strains were screened in a shake flask culture for pyruvate formation from sucrose. The pyruvate accumulated at yields of 0.23–0.57 g pyruvate/g sucrose, and the conversion also was accompanied by the accumulation of some fructose and/or glucose. Selected strains were examined in 1.25 L controlled batch processes with 40 g/L sucrose to obtain time–course formation of pyruvate and monosaccharides. Pyruvate re-assimilation was observed in several strains, which demonstrates a difference in the metabolic capabilities of glucose- and sucrose-grown E. coli cultures. An engineered strain expressing AceE[H106M;E401A] generated 50.6 g/L pyruvate at an overall volumetric productivity of 1.6 g pyruvate/L·h and yield of 0.68 g pyruvate/g sucrose. The results demonstrate that pyruvate production from sucrose is feasible with comparable volumetric productivity and yield to glucose-based processes.