以葡萄糖为碳源合成生物降解性聚酯的研究

MICROBIAL SYNTHESIS AND CHARACTERIZATION OF POLYHYDROXYALKANOATES BY DG17 FROM GLUCOSE

利用从油田土壤中筛选的菌种ＤＧ１７ 以葡萄糖为碳源通过微生物发酵法合成了具有不同结构单元的新型生物可降解性聚合物———聚羟基脂肪酸酯（ＰＨＡｓ） ．初步研究了ＤＧ１７ 以葡萄糖为碳源的生物合成规律，并借助ＧＣ、ＮＭＲ 等分析手段对合成的聚合物进行了结构的分析表征，另外还研究了ＰＨＡｓ 的活性污泥降解情况．研究表明，在限氮条件下，只有碳氮比高于５后，ＤＧ１７ 才能在其体内合成ＰＨＡｓ．在过量碳源的存在下，氮磷比低，得到的聚合物是一种具长侧链的聚（ 羟基辛酸ｃｏ羟基癸酸） 的共聚物，为一种热塑性弹性体．在硫酸铵浓度为０－５ｇ／Ｌ，碳氮比为２０ 条件下合成的Ｐ（ＨＯｃｏＨＤ） 热塑性弹性体的数均分子量为１－１６ ×１０ － ５ ，分子量分散指数为２－４３ ．其玻璃化温度及熔融温度分别为Ｔｇ ＝ － ５２ ℃，Ｔｍ ＝ ５０ ℃．氮磷比高，则合成热塑性塑料ＰＨＢ．结果表明培养基中氮源与磷酸盐的相对浓度是影响ＤＧ１７ 生物合成路径的重要条件．

Poly(3\|hydroxyalkanoates),abbreviated as PHAs are a series of bacterial storage polyesters,currently receiving much attention because of their potential application as biodegradable,biocompatible materials.This paper studied the influence of glucose as the carbon source,nitrogen source,and phosphate on the structure of polymer synthesized by DG17,a mutant isolated from oilfield.The structure of polymer was determined by gas chromatograph(GC),nuclear magnetic resonance(NMR) analysis.Under the experimental conditions,a thermoplastic elastomer P(HO\| co \|HD) with molecular weight 1 16×10 5 was synthesized when concentration of ammonium sulfate were not over 1g/L.But thermoplastics PHB was isolated from cells when concentration of ammonium sulfate was up to 8g/L.During these two concentrations,no polymer was found in cells.Concentrations of nitrogen and phosphate maybe have great influence on the pathway of PHA synthesis.5 was the lowest weight ratio of glucose to ammonium sulfate needed for DG17 to accumulated PHA in cells.Both P(HO\| co \|HD) and PHB synthesized by DG17 from glucose lost up to 90% weights in activated sludge in one month.