FabG Mediates Polyhydroxyalkanoate Production from Both Related and Nonrelated Carbon Sources in Recombinant Escherichia coli LS5218

Abstract

Polyhydroxyalkanoates (PHAs) composed of a mixture of short-chain-length-medium-chainlength (SCL-MCL) hydroxyacyl monomers are biologically produced polyesters that have properties ranging from thermoplastic to elastomeric, dependent on the molar ratio of SCL to MCL monomers incorporated into the copolymer. Because of the potential wide range of properties and applications for SCL-MCL PHA copolymers, it is important to develop and characterize novel metabolic pathways for SCL-MCL PHA production. The current study shows that coexpression of fabG genes from either E. coli or Pseudomonas sp. 61-3 with fabH(F87T) and PHA synthase genes enhances the production of SCL-MCL PHA copolymer from both related and nonrelated carbon sources in Escherichia coli LS5218, indicating the flexibility of FabG as a monomer-supplying enzyme for biological PHA production.

Identification of the Polyhydroxyalkanoate (PHA)-Specific Acetoacetyl Coenzyme A Reductase among Multiple FabG Paralogs in Haloarcula hispanica and Reconstruction of the PHA Biosynthetic Pathway in Haloferax volcanii

“…To our surprise, while the confirmed bacterial PhaBs (GenBank accession no. NP_441203.1, P45375.1, and YP_725942.1) (15,28,36), FabGs (NP_215999 and AAK04872.1) (24,38), and those SDRs with both PhaB and FabG activities (AAA23739.1 and BAE19680.1) (21,22,35) were clustered in several specific subgroups, the haloarchaeal FabG1 to FabG6 proteins were highly divergent from their bacterial counterparts (Fig. 1B).…”

“…Interestingly, although FabGs naturally reduce 3-ketoacyl-ACP to form (R)-3-hydroxyacyl-ACP in fatty acid biosynthesis, a few FabGs also recognize 3-ketoacyl-CoA and hence function in PHA biosynthesis. For example, the FabG proteins of Escherichia coli and Pseudomonas aeruginosa have been demonstrated to supply precursors for PHA biosynthesis in recombinant E. coli cells (21,22,32,35). In addition, several FabG paralogs may have evolved a distinct function, to be responsible only for PHA accumulation.…”

Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) by recombinant Escherichia coli from glucose

“…Therefore, E. coli LS5218 was preferred as a host for the synthesis of P(3HB-co-3HA) copolymers which mcl-3HA units were incorporated. The fadR-deficient E. coli strain LS5218 would be desirable for the synthesis of P(3HB-co-3HA) copolymers from both related and unrelated carbon sources (4,19,32).…”

“…Depending on the monomer structure, PHAs can be divided into three groups. Short chain length PHA (scl-PHA) consisting of monomers with 3e5 carbon atoms, medium chain length PHA (mcl-PHA) consisting of monomers with 6e14 carbon atoms and scl-mcl-PHA copolymers consisting of both scl and mcl monomer units (4). Poly (3-hydroxybutyrate) [P(3HB)], the most extensively member of scl-PHA, has properties of stiff and brittle.…”

High Levels of Bioplastic Are Produced in Fertile Transplastomic Tobacco Plants Engineered with a Synthetic Operon for the Production of Polyhydroxybutyrate

“…While it is currently unknown which endogenous activity in the plastids is capable of catalyzing this reaction, one possible candidate is 3-ketoacyl-acyl carrier protein reductase, an enzyme in the fatty acid biosynthetic pathway. Bacterial equivalents of this enzyme have been used to produce PHAs containing 3-hydroxybutrate monomers in recombinant bacterial hosts (Park et al, 2005;Nomura et al, 2008), and the presence of this enzyme in plant plastids makes it a likely candidate for the low levels of PHB observed in plants transformed with the pCA construct.…”