Biosynthesis of poly(glycolate-co-lactate-co-3-hydroxybutyrate) from glucose by metabolically engineered Escherichia coli

Metabolically engineered Escherichia coli strains were constructed to effectively produce novel glycolate-containing biopolymers from glucose. First, the glyoxylate bypass pathway and glyoxylate reductase were engineered such as to generate glycolate. Second, glycolate and lactate were activated by the Megasphaera elsdeii propionyl-CoA transferase to synthesize glycolyl-CoA and lactyl-CoA, respectively. Third, f3-ketothiolase and acetoacetyl-CoA reductase from Ralstonia eutropha were introduced to synthesize 3-hydroxybutyryl-CoA from acetyl-CoA. At last, the Ser325Thr/GIn481Lys mutant of polyhydroxyalkanoate (PHA) synthase from Pseudomonas sp. 61-3 was over-expressed to polymerize glycolyl-CoA, lactyl-CoA and 3-hydroxybutyryl-CoA to produce poly(glycolate-co-lactate-co-3-hydro-xybutyrate). The recombinant E. coli was able to accumulate the novel terpolymer with a titer of 3.90 g/l in shake flask cultures. The structure of the resulting polymer was chemically characterized by proton NMR analysis. Assessment of thermal and mechanical properties demonstrated that the produced ter-polymer possessed decreased crystallinity and improved toughness, in comparison to poly(3-hydro-xybutyrate) homopolymer. This is the first study reporting efficient microbial production of poly(gly-colate-co-lactate-co-3-hydroxybutyrate) from glucose. (C) 2016 International Metabolic Engineering Society. Published by Elsevier Inc. All rights reserved.