硫酸镁对枯草芽胞杆菌发酵的影响

为明确工业配方中不同MgSO₄添加量对枯草芽胞杆菌B201发酵过程及菌液保存的影响，采用单因素法设置5个MgSO₄添加量梯度(质量分数，下同)( 0.13%、0.24%、 0.46%、0.87%、1.70%)。分别记录不同梯度MgSO₄处理的发酵液灭菌前后pH值，以及发酵过程中的菌体形态的变化，统计发酵结束后细菌的发酵周期、活菌数和芽肥率，测量发酵结束后发酵液pH以及残糖和残氮含量。实验表明，MgSO₄的不同添加量对菌株B201发酵及菌液保存均有显著影响。添加量为0.87%和1.70%处理组灭菌后培养基的pH较灭菌前升高，培养基由中性变为弱碱性。接种后12 h取样观察，菌体明显变形，视野内菌数较少，且随着MgSO₄添加量的增加发酵液活菌数下降，残糖和残氮升高，不利于保存。MgSO₄相对合适的添加量为0.13%、0.24%和0.46%，三种MgSO₄添加量的发酵液活菌数、残氮含量无显著差异；MgSO₄添加量为0.24%时菌株B201芽肥率最高为89.33%，而MgSO₄添加量为0.13%和0.46%时，芽肥率分别为80%和82.67%；0.46%MgSO₄添加量可加速菌株B201发酵进程，发酵周期较其他两个处理缩短45.8%。为提高菌株B201的发酵水平，降低其生产成本，综合考虑MgSO₄的添加量以0.46%为宜。研究结果不仅为实验室菌株B201的发酵优化提供参考，还为培养基的优化拓宽了思路。

Effect of Magnesium Sulfate on Fermentation of Bacillus Subtilis

The purpose of this study was to study the effect of different magnesium sulfate content in industrial formula on the fermentation process and the preservation of Bacillus subtilis B201. Five concentration gradients of magnesium sulfate (0.13%, 0.24%, 0.46%, 0.87%, 1.70%) were set by single factor method. The pH value before and after sterilization of the fermentation liquid treated with different concentrations of magnesium sulfate was recorded spectively, morphology of the bacteria in the fermentation process was observed, the fermentation cycle, the number of viable bacteria and the sporulation rate were counted, and the pH value, the content of residual sugar and nitrogen in the fermentation liquid after fermentation were measured. The results showed that the addition of magnesium sulfate had significant effect on the fermentation and preservation of strain B201. The pH of the treated group with 0.87% and 1.70% magnesium sulfate increased after sterilization, which changed the medium environment from neutral to weak alkaline. Sampling and observation 12 hours after inoculation, the cells were obviously deformed, and the number of bacteria in the field was small,and with the increase of magnesium sulfate, the number of viable bacteria in the fermentation broth decreased, and the residual sugar and nitrogen increased, which was not conducive to preservation. The addition of 0.13%, 0.24% and 0.46% was a relatively appropriate amount of magnesium sulfate, and there was no significant difference in the number of viable bacteria and the content of residual nitrogen in the fermentation liquid of the three groups; the highest sporulation rate of strain B201 was 89.33% in the 0.24% addition group, 80% and 82.67% in the 0.13% and 0.46% addition group, respectively; the fermentation process of strain B201 was accelerated in the 0.46% addition group, and the fermentation cycle was 45.8% shorter than the other two treatments. Considering comprehensively, in order to improve the fermentation level of strain B201 and reduce its production cost,the addition of at magnesium sulfate was suitable. This study not only laid a foundation for the fermentation optimization of the laboratory strain B201, but also broadened the thinking for the optimization of the culture medium.