Enhanced production of poly(lactate-co-3-hydroxybutyrate) from xylose in engineered Escherichia coli overexpressing a galactitol transporter

Appl Microbiol Biotechnol. 2014 Mar;98(6):2453-60. doi: 10.1007/s00253-013-5401-0. Epub 2013 Dec 13.

Abstract

Poly(lactate-co-3-hydroxybutyrate) (P(LA-co-3HB)) was previously produced from xylose in engineered Escherichia coli. The aim of this study was to increase the polymer productivity and LA fraction in P(LA-co-3HB) using two metabolic engineering approaches: (1) deletions of competing pathways to lactate production and (2) overexpression of a galactitol transporter (GatC), which contributes to the ATP-independent xylose uptake. Engineered E. coli mutants (ΔpflA, Δpta, ΔackA, ΔpoxB, Δdld, and a dual mutant; ΔpflA + Δdld) and their parent strain, BW25113, were grown on 20 g l(-1) xylose for P(LA-co-3HB) production. The single deletions of ΔpflA, Δpta, and Δdld increased the LA fraction (58-66 mol%) compared to BW25113 (56 mol%). In particular, the ΔpflA + Δdld strain produced P(LA-co-3HB) containing 73 mol% LA. Furthermore, GatC overexpression increased both polymer yields and LA fractions in ΔpflA, Δpta, and Δdld mutants, and BW25113. The ΔpflA + gatC strain achieved a productivity of 8.3 g l(-1), which was 72 % of the theoretical maximum yield. Thus, to eliminate limitation of the carbon source, higher concentration of xylose was fed. As a result, BW25113 harboring gatC grown on 40 g l(-1) xylose reached the highest P(LA-co-3HB) productivity of 14.4 g l(-1). On the other hand, the ΔpflA + Δdld strain grown on 30 g l(-1) xylose synthesized 6.4 g l(-1) P(LA-co-3HB) while maintaining the highest LA fraction (73 mol%). The results indicated the usefulness of GatC for enhanced production of P(LA-co-3HB) from xylose, and the gene deletions to upregulate the LA fraction in P(LA-co-3HB). The polymers obtained had weight-averaged molecular weights in the range of 34,000-114,000.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Escherichia coli / enzymology*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism*
  • Galactitol / metabolism*
  • Gene Deletion
  • Gene Expression
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Metabolic Engineering*
  • Polyesters / metabolism*
  • Xylose / metabolism*

Substances

  • Membrane Transport Proteins
  • Polyesters
  • Galactitol
  • Xylose