화학공학소재연구정보센터
Journal of Bioscience and Bioengineering, Vol.120, No.3, 305-310, 2015
Biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyalkanoates) by recombinant Escherichia coli from glucose
The polyhydroxyalkanoate (PHA) copolymers consisting of short-chain-length (Scl) and medium-chain-length (mcl) monomers have various properties ranging from stiff to flexible depending on the molar fraction of the monomer compositions. It has been reported that PhaG, which is first known as a (R)-3-hydroxyacyl-acyl carrier protein (ACP)-CoA transferase, actually functions as a 3-hydroxyacyl-ACP thioesterase, and the product of PP0763 gene from Pseudomonas putida KT2440 has a (R)-3-hydroxyacyl (3HA)-CoA ligase activity (Wang et al., Appl. Environ. Microbiol., 78, 519-527, 2012). In this study, we found a new (R)-3HA-CoA ligase (the product of PA3924 gene) from Pseudomonas aeruginosa PAO. The PA3924 gene was coexpressed with PHA synthase 1 gene (phaC1(Ps)) and phaG(Ps) gene from Pseudomonas sp. 61-3, and beta-ketothiolase gene (phbA(Re)) and acetoacetyl-CoA reductase gene (phbB(Re)) from Ralstonia eutropha in Escherichia coli LS5218 at 25 degrees C. As a result, the copolymer containing 94.6 mol% 3-hydroxybutyrate (3HB) and 5.4 mol% mcl-3-hydroxyalkanoates (3HA) consisting of C-8, C-10, C-12 and C-14 was synthesized by recombinant E. coli LS5218 from glucose as the sole carbon source. The concentration of P(3HB-co-3HA) (scl-co-mcl-PHA) synthesized by the recombinant E. coli LS5218 harboring phaC1(Ps), phaG(Ps), phbAB(Re) and the PA3924 genes was approximately 7-fold higher than that of the recombinant LS5218 harboring phaC1(Ps), phaG(Ps), phbAB(Re) and the PP0763 genes. The number-average molecular weight of the P(3HB-co-5.4% 3HA) copolymer was 233 x 10(3), which was relatively high molecular weight. In addition, the physical and the mechanical properties of the copolymer were demonstrated to improve the brittleness of P(3HB) homopolymer. (c) 2015, The Society for Biotechnology, Japan. All rights reserved.