自养黄杆菌合成羟基丁酸和羟基戊酸共聚体的发酵研究

STUDIES ON FERMENTATION OF SYNTHESIZING POLY(HYDROXYBUTYRATE-CO-HYDROXYVALERATE) BY XANTHOBACTER AUTOTROPHICUS

采用本实验室从土壤中分离到的一株自养黄杆菌进行了羟基丁酸和羟基戊酸共聚体〔P(HB-co-HV)〕的发酵试验。实验结果表明,该菌株是自养黄杆菌葡萄糖运输突变株,可以葡萄糖、果糖、蔗糖、麦芽糖、乙酸盐、乳酸盐和苹果酸盐作为唯一碳源,尤以葡萄糖和果糖效果最佳。硫酸铵、氯化铵和蛋白胨等不同氮源不影响其生长,却影响细胞中P(HB-co-HV)的含量和P(HB-co-HV)中HV/HB的比例。应用两阶段控制方式,经42h的补料分批发酵,细胞浓度达34.9g·L^(-1),P(HB-co-HV)浓度达25.28g·L^(-1)。细胞和P(HB-co-HV)生产速率系数分别为0.83g·L^(-1)”·h^(-1)和0.61g·L^(-1)·h^(-1)。以基质为基准的细胞得率系数(Yx/s)、产物得率系数(Yp/s)和以干细胞为基准的产物得率系数(Yp/x)分别为0.283(g/g)、0.174(g/g)和0.73(g/g)。改变培养基中碳氮源组分可将P(HB-co-HV)中HB的含量调节在24％～78％之间。

Fermentation test of P( HB-co-HV) was carried out by a Xanthobacter autotrophicus strain which was isolated from soil by our laboratory. The resultes show that the strain is a transport mutant strain for glucose. Glucose, fructose, sucrose, maltose, acetate, propionate, lactate or malate was utilized as sole carbon source, but glucose and fructose were the best among carbon sources. The growth was not affected by (NH4)2SO4 NH4C1 and peptone as different nitrogen sources, but P(HB-co-HV) content of dry cell and the HV/ HB ratio of P(HB-co-HV) were affected. The fed-batch fermentation was carried out for 42h using two-stage cantrolling method. The final cell concentration of 34.9 g . L-1 and the final P(HB-co-HV) concentration of 25.48g . L-1 were obtained in the glucose broth. The cell productivity and P( HB-co-HV) productivity were 0.83g. L-1 .h-1 and 0.61g . L- 1. h-1, respectively. The yield of dry cell to the substrate (Tx/sX the yield of P(HB-co-HV) to the substrate (Yx/s) and the yield of P(HB-co-HV) to the dry cell (Yp/x) were 0.283(g/ g),0.174(g/ g) and 0.730(g / g), respectively. The HB content in the P (HB-co-HV) was adjusted from 24% to 78% by changing the carbon and nitroge component of the medium.