Establishment of a carbon-efficient xylulose cleavage pathway in Escherichia coli to metabolize xylose

As the second-largest storage saccharide in the world, xylose is a promising renewable feedstock in the bio-industry. A few microorganisms can metabolize xylose naturally via the xylose isomerase pathway, Weimberg pathway, or Dahms pathway. In this study, we reported the metabolic engineering of Escherichia coli to achieve the carbon-efficient utilization of xylose through the establishment of a rationally designed xylulose cleavage pathway. With the inactivation of ribulose-phosphate 3-epimerase and expression of exogenous phosphoketolase, the engineered E. coli accumulated acetate as a major byproduct using xylose as the sole carbon source. Furtherly, acetate production pathways were successfully blocked to provide sufficient acetyl-CoA precursor for downstream biosynthesis reactions. Finally, we applied the xylulose cleavage pathway to produce poly-3-hydroxybutyrate. Our proposed metabolic engineering strategies illustrate the feasibility of efficient xylose utilization to produce commodity chemicals. • Xylose assimilation was blocked by rpe deletion in Escherichia coli . • The carbon-efficient xylulose cleavage pathway was constructed. • Acetate formation was eliminated through poxB and ackA deletion. • Engineered E. coli produced PHB through xylulose cleavage pathway.