Accumulation of d -Glucose from Pentoses by Metabolically Engineered Escherichia coli

Abstract

ABSTRACT Escherichia coli that is unable to metabolize d -glucose (with knockouts in ptsG , manZ , and glk ) accumulates a small amount of d -glucose (yield of about 0.01 g/g) during growth on the pentoses d -xylose or l -arabinose as a sole carbon source. Additional knockouts in the zwf and pfkA genes, encoding, respectively, d -glucose-6-phosphate 1-dehydrogenase and 6-phosphofructokinase I ( E. coli MEC143), increased accumulation to greater than 1 g/liter d -glucose and 100 mg/liter d -mannose from 5 g/liter d -xylose or l -arabinose. Knockouts of other genes associated with interconversions of d -glucose-phosphates demonstrate that d -glucose is formed primarily by the dephosphorylation of d -glucose-6-phosphate. Under controlled batch conditions with 20 g/liter d -xylose, MEC143 generated 4.4 g/liter d -glucose and 0.6 g/liter d -mannose. The results establish a direct link between pentoses and hexoses and provide a novel strategy to increase carbon backbone length from five to six carbons by directing flux through the pentose phosphate pathway.