Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by recombinant Escherichiacoli harboring propionyl-CoA synthase gene (prpE) or propionate permease gene (prpP)

In order to enhance 3-hydroxyvalerate (3HV) fraction in copolyesters of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), the propionate permease gene prpP or the propionyl-CoA synthase gene prpE was transformed into Escherichia coli XL10-Gold with co-expression of PHB operon (phaCAB) from Ralstonia eutropha. The recombinant E. coli strains were cultured on mixed carbon sources composed of glucose and propionic acid to promote PHBV accumulation. It was shown that the over-expression of prpE suppressed 3HV incorporation into PHBV copolymer, which led to reduced 3HV fraction. In contrast, the over-expression of prpP improved the 3HV content from 5.6 to 14.3 mol%, followed by an increased PHBV accumulation up to 62 wt%. The results showed that the expression of prpP stimulated the uptake and utilization of propionic acid and increased the 3HV fraction in PHBV. However, the over-expression of prpE in E. coli did not affect 3HV content in PHBV. Surprisingly, co-expression of prpE and prpP did not lead to any 3HV formation. This study showed the possibility to change the PHBV composition without overdose of propionic acid which is expensive and toxic for the cells.