保加利亚乳杆菌是酸奶发酵剂和益生菌制剂的重要菌种,其高密度培养对于提高菌种在应用产品生产中的效率具有重要的现实意义。葡萄糖浓度和发酵pH是影响保加利亚乳杆菌生长的关键因子,底物葡萄糖被转化为细胞菌体和主要代谢产物乳酸,探究葡萄糖消耗速率与表征乳酸生成的发酵pH下降速率的关系,是研究保加利亚乳杆菌代谢流方向的重要方法。该实验通过培养基组成和培养条件对保加利亚乳杆菌生长的影响进行研究,同时对葡萄糖消耗速率-pH降低速率相关模型研究,并基于底物质量守恒定律建立了一条基于pH下降速率的保加利亚乳杆菌高密度培养的反馈补料发酵策略。通过化学中和法控制发酵pH为6.0~5.0,基于pH下降速率进行反馈补料将葡萄糖质量浓度控制在8~2 g/L,发酵液的活菌数达到3.6×109 CFU/mL,是批次分批培养的2.4倍。该策略的应用结果为提高保加利亚乳杆菌的工业化生产效率提供参考。
Lactobacillus bulgaricus is an essential strain of yogurt starter and probiotic preparations.Its high-density culture has practical significance for improving production efficiency of the strain applied products.Glucose concentration and fermentation pH are key factors affecting the growth of Lactobacillus bulgaricus.The substrate glucose is converted into cellular bodies, and the main metabolite is lactic acid.In particular, the study of the rate of glucose consumption in relation to the rate of decrease in fermentation pH characterizing lactic acid production is an essential method to study the direction of metabolic flow in Lactobacillus bulgaricus.In this study, the effect of medium composition and culture conditions on the growth of Lactobacillus bulgaricus and the correlation model of glucose consumption rate-pH decrease rate was studied.Based on the conservation law of substrate mass, a feedback strategy for a high-density culture of Lactobacillus bulgaricus based on the pH decrease rate was established.The pH of fermentation was controlled within the interval of 6.0-5.0 using the chemical neutralization method, and the glucose concentration was controlled within the interval of 8-12 g/L by feedback feeding based on the pH decrease rate.The number of live bacteria in the fermentation liquid reached 3.6×109 CFU/mL, 2.4 times that of batch culture.The application results of this strategy provide a reference for improving the industrial production efficiency of Lactobacillus bulgaricus.
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