蜡样芽孢杆菌高密度发酵条件与过程的优化

Optimization of High Cell Density Fermentation Conditions and Process of Bacillus cereus

摘要:

蜡样芽孢杆菌的生物量对其生物功能具有重要影响。为了提高蜡样芽孢杆菌的产量与芽孢率，通过单因素实验筛选出最适宜其生长的碳源与氮源，分别为质量比1∶1复配的葡萄糖与水溶性淀粉和质量比1∶1复配的大豆蛋白胨与酵母提取物。在此基础上，于7 L发酵罐中探究流加方式、pH、搅拌转速和通气量等因素对其生物量及芽孢率的影响。最优发酵条件为：在0~9 h之间，转速250 r/min，通气量3 L/min，pH恒定6.5；9~18 h时，转速升高至350 r/min，通气量升高至4.5 L/min，并以0.45 mL/min流量补加培养基浓缩液；18 h时，转速降低至150 r/min，通气量降低至2.25 L/min，pH调高至7.5，停止补料至发酵结束。基于以上发酵策略，在18 h时，蜡样芽孢杆菌活菌数达2.2×10¹⁰ CFU/mL，是未优化前的4.88倍；发酵结束时，芽孢率超过90%。本研究结果为蜡样芽孢杆菌的工业化应用提供了一定基础。

Abstract:

The biomass of Bacillus cereus has an important effect on its biological function. In order to increase the yield and spore rate of Bacillus cereus, the optimum carbon and nitrogen source were screened by single factor experiment. The optimal carbon source was 1∶1(mass ratio) mixed glucose and water-soluble starch, and the optimal nitrogen source was 1∶1(mass ratio) mixed soybean peptone and yeast extract. The effects of feeding method, pH, stirring speed and ventilatory capacity on the biomass and spore rate were studied in a 7 L bioreactor. The optimal fermentation conditions were as follows: in 0~9 h, the stirring speed, aeration ratio and pH were 250 r/min, 3 L/min and 6.5, respectively; in 9~18 h, the stirring speed and ventilatory capacity were 350 r/min and 4.5 L/min, respectively and the concentrated medium was added at a flow rate of 0.45 mL/min; at 18 h, the stirring speed, ventilatory capacity and pH were changed to 150 r/min, 2.25 L/min and 7.5 respectively, and the feeding was stopped till the end of fermentation. Based on the above fermentation strategies, the number of viable Bacillus cereus reached 2.2×10¹⁰ CFU/mL at 18 h, which was 4.88 times of that before the optimization. At the end of fermentation, the spore rate was over 90%. This study provided basis for the industrial applications of Bacillus cereus.