Engineering of Ralstonia eutropha for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) from glucose

• Seven strains were generated from R. euthropha for PHBV production without propionate addition.
• These strains accumulated PHBVs, accounting for 59.4–70.3% of CDW, with 3HV ratios of 0.4–29.5 mol%.
• PHBV production and 3HV fraction (in mol%) were 94.4 g/L and 4.8 for Rem-2, and 90.6 g/L and 26.0 for Rem-8, respectively.

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with Ralstonia eutropha relies on the addition of propionate during fermentation, and propionate consumption is one of the major factors affecting the cost of PHBV production. In this study, 7 strains were obtained by genetic manipulating the methylcitric acid cycle and the methylmalonyl-CoA pathway in R. eutropha. Disruption of prpC1 and prpC2 genes did not affect cell growth and PHBV accumulation. All 7 strains were able to accumulation high amounts of PHBVs with 3HV fractions of 0.41–29.1 mol% during cultivation in flasks. Fermentation in 7.5-L fermenter showed that genetically engineered Rem-8 was able to yield biomass of 132.8 CDW g/L, of which 68.6% were PHBV with 3HV fraction of 26.0 mol% in the biopolymer, indicating promising potentials of commercialization in the future.