Bio-synthesis of poly(lactic acid) by wild type PHA-producing bacteria

聚乳酸（PLA）是一种利用植物中的可再生资源合成的生物基高分子材料。我们最近发现在真养罗尔斯通氏菌（Ralstonia eutropha）的微生物培养体系中存在聚乳酸寡聚体。eutropha），已知其在其体内形成其它脂肪族聚酯、聚（3-羟基丁酸酯）。本研究的目的是寻找最佳的细胞培养条件，以更好的大规模生产和更高的聚乳酸分子量，建立在温和的条件下的聚酯的合适的积累方式。从R.真养型培养体系中的乳酸重复单元主要由D型乳酸重复单元组成，而巨大芽孢杆菌培养体系中的乳酸重复单元主要由D型乳酸重复单元和L型乳酸重复单元组成。PLA中乳酸单元的光学纯度取决于细胞株。我们还发现，我们的细胞条件不能导致大规模生产或高分子量的聚乳酸。即使是现在，我们也在努力寻找最佳的细胞培养条件。

Poly(lactic acid) (PLA) is one of bio-based polymers synthesized from renewable resources in plants. We have recently found that PLA oligomers existed in a microbial cultured system of Ralstonia eutropha (R. eutropha), which is known to form other aliphatic polyester, poly(3-hydroxybutyrate) within its body. This research aimed to find optimal cell-culture conditions for both better mass production and higher molecular weight of PLA, establishing the suitable accumulation manner of the polyester under mild conditions. PLA obtained from R. eutropha culture system was found to composed of D-formed lactic acid repeating units, while that from other strain cell, Bacillus megaterium, contained D- and L-formed ones. The optical purity of lactic acid units in PLA depended on the cell strains. It was also found that our cell conditions could not result in large mass production or high molecular weight of PLA. Even now, we are trying to find out the optimal cell-culture conditions.