需钠弧菌(Vibrio natriegens)合成聚羟基丁酸的研究

研究结果表明，V.natriegens可以利用葡萄糖，果糖，以及糖蜜为碳源合成聚羟基丁酸[Poly(3HB)] ,当以糖蜜为碳源时，积累的Poly(3HB)达到细胞干重的28．4％，实验结果还表明，Poly(3HB)的积累滞后于细胞生长，在培养前加入过量的碳源，不仅没有Poly(3HB)积累，还抑制细胞的生长，测定了与Poly(3HB)合成相关的PHA聚合酶，β-酮硫解酶和乙酰乙酰CoA还原酶的活性。结果表明，伴随Poly(3HB)合成，PHA聚合酶活性从无到有，β－酮硫解酶活性提高了10倍以上。进一步通过利用脂肪酸合成代谢抑制物－浅蓝菌素（cerulenin)，研究了脂肪酸从头合成途径与Poly(3HB)合成途径的关系。发现浅蓝菌素能够明显降低细胞Poly(3HB)的累积。根据以上结果，推测在V.natrigens中可能存在两条代谢途径参与Poly(3HB)的合成。

Biosynthesis and Accumulation of Poly(3-hydroxybutyrate) in Vibrio natriegens

Accumulation of poly(3-hydroxybutyrate) [poly(3HB)] by V. natriegens was studied. Results indicated that V. natriegens used glucose, gluconate, fructose and molasses as carbon sources for poly(3HB) synthesis. When molasses was used, up to 28.4% of poly(3HB) to cellular dry weight was accumulated. The accumulation of poly(3HB) followed, was not simultaneously to, the cell growth. Analysis of the PHA polymerase, beta-ketothiolase, and acetoacetyl-CoA reductase showed that the poly(3HB) accumulation was correlated to the increase of their activities in cells. Poly(3HB) accumulation was also related to the de novo fatty acid synthesis, as revealed by the results that cerulenin, a specific inhibitor to the de novo fatty acid synthesis, significantly reduced accumulation of poly(3HB). Based on the results from this study, the synthetic pathway of poly(3HB) was proposed.