title: Enhanced production of poly(lactate-co-3-hydroxybutyrate) from xylose in engineered Escherichia coli overexpressing a galactitol transporter.
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.
authors: Division of Biotechnology and Macromolecular Chemistry, Graduate School of Engineering, Hokkaido University, N13-W8, Kita-ku, Sapporo, 060-8628, Japan.
authors: John Masani
authors: JM
authors: Nduko
authors: Ken'ichiro
authors: K
authors: Matsumoto
authors: Toshihiko
authors: T
authors: Ooi
authors: Seiichi
authors: S
authors: Taguchi
mesh_terms: D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D004376:Galactitol / Q000378:metabolism*; D017353:Gene Deletion; D015870:Gene Expression; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D060847:Metabolic Engineering; D011091:Polyesters / Q000378:metabolism*; D014994:Xylose / Q000378:metabolism*
chemical_list: D026901:Membrane Transport Proteins; D011091:Polyesters; D004376:Galactitol; D014994:Xylose