Departmental Bulletin Paper 〈PAPERS and REPORTS〉Preparation of genetic engineered Enterobacter strain TF to produce green plastic from xylose

Mori, Shunya  ,  Yamamoto, Kojiro  ,  Matsumoto, Katsuki  ,  Hokamura, Ayaka  ,  Matsusaki, Hiromi  ,  Tanaka, Kenji

Polyhydroxyancanoate (PHA) is a bacterial polyester which is thermoplastic, flexible and biodegradable. PHA is expected as “green plastic” material therefore many researchers have been studying the development of new type PHAs, their physical property, biodegradability and the production method. In commercial production of PHA, use of substances obtained from biomass as economic and ecological carbon sources is necessary. Hemicellulose, which is mainly composed of glucose, xylose and other monosaccharaides is an important biomass, however xylose is not very feasible sugar to be used as substrate in fermentation. Our isolated bacterium, Enterobacter sp.TF grow vigorously on xylose, arabinose and other many kind of sugars but it does not accumulate PHA. Hence, we made genetic engineering to the strain TF by inserting the genes for PHA biosynthesis from Ralstonia eutropha which is well known as PHB producer, and from Pseudomonas sp.61-3 which is one of the few bacteria to produce PHA copolymer from glucose. As, result, our recombinant of Enterobacter sp.TF did not produce PHA copolymer but produced about 20wt% PHB homopolymer per dried cells.キシロースは、農産廃棄物や廃材など植物性バイオマスに含まれるヘミセルロースの主要構成単糖であり、発酵原料等への有効利用法の開発が急がれている。しかしながら、キシロースは微生物にとって利用しやすい糖であるとは言い難く、また工業的に利用価値のある発酵生産物も少ないのが現状である。ある種の微生物が産生するポリヒドロキシ酪酸(PHB)やポリヒドロキシアルカン酸(PHA)などのポリエステルは、熱可塑性と生分解性を併せ持つため“グリーンプラスチック”として期待されており、植物由来の有機物を原料基質として使えばCO2の排出量を増やさない“カーボンニュートラル”なプラスチックにもなりえる。本研究では、独自に分離したキシロース高資化性のEnterobacter属細菌にPHAやPHBの生合成遺伝子を導入した組換え株を作製し、実際にキシロースからこれらグリーンプラスチックを合成するか検証した。

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