Production of heteropolymeric polyhydroxyalkanoate in Eschericha coli from a single carbon source

Arthur C. Eschenlauer, Sandra K. Stoup, Friedrich Srienc, David A. Somers

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Poly[β-hydroxybutyrate-co-β-hydroxyvalerate] co-polymer, PHBV, is a polyhydroxyalkanoate (PHA) that has greater utility as a biodegradable thermoplastic polyester than poly-β-hydroxybutyrate, PHB. In order to produce PHBV, a system of pathways is required to produce both hydroxybutyrate (HE) and hydroxyvalerate (HV) monomers from the sources of carbon. A working model for conversion of glucose to PHBV via acetyl- and propionyl-coenzyme A was constructed by expressing the PHA biosynthesis genes from Alcaligenes eutrophus in Escherichia coil strain K-12 under novel growth conditions. When 1 mM valine was added to 1% glucose medium, growth ceased and up to 2.5% of the incorporated monomers were HV; up to 4% were HV when 1 mM threonine was added as well. Threonine dehydratase (TD) converts threonine to α-ketobutyrate; TD is required for HV to be incorporated into PHA unless its transaminated reaction product, α-aminobutyrate, is added to the medium. Intracellular α-ketobutyrate accumulates when valine is added to the medium because valine, which cannot be metabolized to HV by E. coli strain K-12, stimulates TD and inhibits acetolactate synthase. In turn, α-ketobutyrate is converted to propionyl-CoA by the E. coil pyruvate dehydrogenase complex. This constitutes a defined system of pathways for synthesis of a heteropolymeric PHA from a single carbon source, which in the future could be transferred to other organisms including plants.

Original languageEnglish (US)
Pages (from-to)121-130
Number of pages10
JournalInternational Journal of Biological Macromolecules
Volume19
Issue number2
DOIs
StatePublished - Aug 1996

Keywords

  • Poly-β-hydroxyalkanoic acids
  • Poly[β-hydroxybutyrate-co-β-hydroxyvalerate] co-polymer
  • Propionyl co-enzyme A
  • Pyruvate dehydrogenase
  • Threonine
  • Threonine dehydratase
  • α-ketobutyrate

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