[Effect of reducing the activity of respiratory chain on biosynthesis of poly(3-hydroxybutyrate-co-lactate) in Escherichia coli]

Poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)] belongs to the polyhydroxyalkanoates (PHA) family and possesses promising properties including biocompatibility and biodegradability. In this study, we directly synthesized P(3HB-co-LA) with glucose by introducing the β-ketothiolase and acetoacetyl-CoA reductase from Ralstonia eutropha, the engineered propionate CoA transferase from Clostridium propionicum and the engineered polyhydroxyalkanoate synthase from Pseudomonas fluorescens strain 2P24 into Escherichia coli. The polymer content was 83.9% (W/W), and the molar percentage of lactate reached 1.6%. On this basis, in order to accumulate lactate, we reduced the activity of respiratory chain by deleting the ubiX gene, which is involved in the synthesis of coenzyme Q8. Moreover, we removed the dld gene to avoid the conversion of lactate to pyruvate during the fermentation. With these manipulations, the molar percentage of lactate in the polymer was improved to 14.1%, with an 81.7% (W/W) of polymer content. The test results indicated that the strategy of reducing the activity of respiratory chain effectively increased the lactate units in the polymer, and it contributed a new approach to change the content of monomer components in the polymer.