Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) copolymer from sugars by recombinant Ralstonia eutropha harboring the phaC1Ps and the phaGPs genes of Pseudomonas sp. 61-3.

Abstract

Heterologous expression of the phaGPs and the phaClPs genes encoding 3-hydroxyacyl acyl carrier protein-coenzyme A transacylase and polyhydroxyalkanoate (PHA) synthase from Pseudomonas sp. 61-3, respectively, was performed in the phbCRe negative mutant, Ralstonia eutropha PHB-4. The recombinant strain of the R. eutropha PHB-4 produced PHA copolymers consisting of 3-hydroxybutyrate (3HB) and medium-chain-length 3-hydroxyalkanoate (mcl-3HA) units of 6-12 carbon atoms from sugars. The 3HB fraction in copolymers was very high (95-97 mol%). The PHA content in the recombinant strain could further be increased by the additional introduction of the phbABRe genes from R. eutropha encoding beta-ketothiolase and NADPH-depedent acetoacetyl-coenzyme A reductase. Differential scanning calorimetry analysis of the PHA copolymers produced by the recombinant R. eutropha PHB-4 have indicated that the PHA is a random copolymer of 3HB and mcl-3HA units.