Optimization of Spore Production in Bacillus coagulans Using Response Surface Methodology Approach

Due to its spore-forming ability, Bacillus coagulans has advantages over the other non-spore-forming probiotics. Among them, survival and stability during food processing and storage, resistance to acid pH, and digestive enzymes are important. However, there are few studies on the quality and amount of sporulation in B. coagulans. This study investigated the spore densities and formation efficiency of B. coagulans. The optimal medium formulation consisted of yeast extract (1.00 g L^-1), potassium acetate (20.00 g L^-1), and MnSO₄ (0.01 g L^-1 and 0.03 g L^-1). After reaching the optimal medium, a response surface regression equation was established based on the results of central composite design (CCD) experimental designs to optimize time, temperature, and pH parameters. The predicted results thus obtained were in good agreement (R² = 95.19%) with the results obtained by performing experiments. Multiple regression analysis and analysis of variance (ANOVA) showed that pH is negative, and temperature and time dose are positive factors. The maximum spore cell densities by optimization plots have obtained 9.80 log at temperature 83.77 °C, pH 3.05, and time 111.19 h, considering that B. coagulans needs special environmental and cellular conditions to enter the sporulation stage. In this study, the composition of the culture medium and factors such as temperature, time, and pH were considered influencing factors in B. coagulans sporulation.