Establishment of a metabolic pathway to introduce the 3-hydroxyhexanoate unit into LA-based polyesters via a reverse reaction of β-oxidation in Escherichia coli LS5218

New lactate (LA)-based terpolymers, P[LA-co-3-hydroxybutyrate (3HB)-co-3-hydroxyhexananoate (3HHx)]s, were produced in recombinant Escherichia coli LS5218 harboring three genes encoding LA-polymerizing enzyme (LPE), propionyl-coenzyme A (CoA) transferase (PCT) and (R)-specific enoyl-CoA hydratase (PhaJ4). When the recombinant LS5218 was grown on glucose with the feeding of butyrate, 3HB-CoA and 3HHx-CoA were supplied, probably via reverse reactions of the β-oxidation pathway and PhaJ4. LPE copolymerized the two monomers 3HB-CoA and 3HHx-CoA with LA-CoA, which was generated by PCT, to yield the terpolymers. Gas chromatography analysis revealed that the terpolymers consisted of 2.7-34 mol% LA, 38-81 mol% 3HB and 17-33 mol% 3HHx units, which can be varied depending on the butyrate concentration fed in the medium. In addition, 1H-13C COSY NMR analysis provided evidence for a linkage between LA and 3HHx units in the polymer.