关键词: 凝结芽孢杆菌, 芽孢形成, 碳酸钙, 芽孢抗性, 基因表达

Abstract: The effect of calcium carbonate on the sporulation of Bacillus coagulans CGMCC 9951 and its possible mechanism were studied in this investigation. The results showed that addition of 6% CaCO3 to the fermentation broth at 16 h not only ensured sufficient supply of calcium for sporulation, but also increased the pH of the fermentation broth from about 4 to over 6.5, quickly initiating sporulation. At (68 ± 2) h, the concentration of spores reached 4.53 × 107 CFU/mL, and sporulation was initiated about 100 hours earlier compared with the control group. Moreover, the heat resistance, acid resistance, bile salt tolerance and germination ability of spores were not significantly affected by CaCO3. Further we found that addition of CaCO3 effectively accelerated the sporulation process. The expression levels of kinC, kinE and spo0A genes related to sporulation initiation were significantly increased at 4 h after adding CaCO3, reaching levels 61.07, 23.49, and 17.32 times as high as the control group, respectively. This study revealed that the sporulation of B. coagulans was dependent upon environmental pH and neutral and weakly alkaline environments were conducive to the transcription of sporulation-related genes, thus accelerating the sporulation process.

Key words: Bacillus coagulans, sporulation, CaCO3, spore resistance, gene expression