Abstract: Bacillus coagulans is one of the most important probiotics with the characteristics of both lactic acid bacteria and Bacillus. In recent years, it has attracted more and more attention. However, the study on the sporulation pathway and regulation mechanism of Bacillus coagulans is relatively scarce. The effect of calcium carbonate addition on sporulation of Bacillus coagulans CGMCC 9951 and its possible mechanism were mainly studied in this paper. The results showed that the addition of 6% CaCO3 at 16 h not only ensured sufficient calcium requirement for sporulation, but also promoted the pH of fermentation broth from about 4 to over 6.5, and quickly initiated sporulation. At 68±2 h, the sporulation amount reached 4.53×107 CFU/mL, which sporulation initiation time was about 100 hours earlier than the control group, and the heat resistance, acid resistance, bile salt tolerance and germination ability of the spores were not significantly affected. Further studies found that the addition of CaCO3 effectively promoted the sporulation process of Bacillus coagulans CGMCC 9951. The expression of kinC, kinE and spo0A which related to sporulation initiation was significantly increased after adding CaCO3 for 4 h, which was 61.07 times, 23.49 times, 17.32 times of the control group, respectively. This study preliminarily revealed that the sporulation of Bacillus coagulans had a certain environmental pH dependence, and the neutral alkaline environment was conducive to the sporulation initiation of gene transcription, thus accelerating the sporulation process.

Key words: Bacillus coagulans, sporulation, CaCO3, spore resistant, gene express