PHB高产菌株的选育和发酵条件研究

Selection of Mutants and Optimization of Fermentation Conditions for PHB-Producing Strain

采用化学诱变剂(亚硝基胍)对积累聚β-羟基丁酸酯(PHB)的蜡状芽孢杆菌产生菌13进行诱变处理,筛选突变株,通过比较PHB产量,获得了两株高产菌株分别命名为蜡状芽孢杆菌13(3)和13(5),其PHB产量分别为29.58,29.29g/L,与出发菌株相比较,PHB产量提高了17.8%和16.6%.对出发菌株13和突变菌株13(3)的生长曲线和产PHB进程曲线进行了测定,在37℃培养条件下出发菌株13和突变菌株13(3)的PHB产量均在16h时达到最大.在32℃培养条件下出发菌株13培养80h和诱变菌13(3)培养60h时PHB产量达到最大,该突变株在37℃比在32℃培养时发酵周期缩短了73.3%,而PHB的积累量相当.正交实验结果表明,突变菌株13(3)产生PHB的最佳发酵条件为:碳源为葡萄糖、氮源为硫酸铵,碳氮比为2∶1时,pH值为7.5,培养温度为37℃,发酵周期为16h.

The mutants of Bacillus cereus 13 accumulating poly-β-hydroxybutyrate（PHB）were screened through the chemical mutagens（Nitrosoguanidine）.Among these mutants,the PHB productions of Bacillus cereus 13（3）and13（5）were 29.58g/L and 29.29g/L,and increased by 17.8%and 16.6%than the wild type strain,respectively.The growth curve and PHB production process curves of the wild type strain 13 and mutant strain 13（3）were measured at 37℃and 32℃.As the results shown,the PHB accumulation yields of the wild type strain 13 reached the peak values at 16 hin 37℃and at 80 hin 32℃,respectively;and the mutant strain 13（3）reached the peak values at 16 hin 37℃and at 60 hin 32℃,respectively.The fermentation period of mutant strain 13（3）was shortened by73.3%at 37℃than at 32℃.The orthogonal experiments were designed for researching into the optimal fermentation conditions of the mutant strain 13（3）.The optimum fermentation conditions for the mutant 13（3）were glucose as the carbon source,ammonium sulfate as the nitrogen source,C/N ratio of 2∶1,pH value 7.5,the fermentation temperature for 37℃,and the fermentation period for 16 h.