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C. T. Nomura¹, T. Tanaka¹, Z. Gan¹, K. Kuwabara¹, H. Abe^1,2, K. Takase¹,

K. Taguchi¹, and Y. Doi^1,2

 ¹ Polymer Chemistry Laboratory, RIKEN Institute, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan

² Department of Innovative and Engineered Materials, Tokyo Institute of Technology, 4259 Nagatuta, Midori-ku, Yokohoma 226-8502, Japan

Keywords: Polyhydroxyalkanoates; substrate specificity altered PHA synthase; 3-ketoacyl-ACP synthase III; fatty acid biosynthesis; Escherichia coli

      Polyhydroxyalkanoates (PHAs) are biodegradable polyesters that have a wide variety of physical properties dependent on the lengths of the pendant groups of the monomer units in the polymer. PHAs composed of mostly short-chain-length (SCL) monomers are often stiff and brittle, whereas PHAs composed of mostly medium-chain-length (MCL) monomers are elastomeric in nature. SCL-MCL PHA copolymers can have properties between these two states, dependent on the ratio of SCL and MCL monomers in the copolymer. It was found previously that SCL-MCL PHA copolymer composed of mostly SCL monomer units with a small mol% of MCL has superior qualities compared to the SCL homopolymer, P(3HB). Therefore, it is desirable to elucidate new and low cost ways to produce PHA monomers from renewable resources for the production of SCL-MCL PHA copolymer. In order to address this issue, we have created strains of recombinant E. coli capable of producing β-ketothiolase (PhbA) and acetoacetyl-CoA synthase (PhbB) from Ralstonia eutropha, genetically engineered 3-ketoacyl-ACP synthase III (FabH) from Escherichia coli, and genetically engineered PHA synthases (PhaC) from Pseudomonas sp. 61-3 to enhance the production of SCL-MCL PHA copolymer from glucose. The cumulative effect of having two monomer-supplying pathways and genetically engineered PHA synthases resulted in higher accumulated amounts of SCL-MCL PHA copolymer from glucose. Polymers were isolated from two recombinant E. coli strains, the first harboring the phbAB, fabH (F87T), and phaC1 (SCQM) genes and the second harboring the phbAB, fabH (F87W), and phaC1 (SCQM) genes.

      論文來源：International Symposium on Biological Polyesters ,Auguest 22-27, 2004