Isolation, functional evaluation, and fermentation process optimization of probiotic Bacillus coagulans.

Bacillus coagulans is a probiotic agent widely used in various industries. In this study, we isolated a novel strain of B. coagulans, X26, from soil and characterized its properties. X26 exhibited superior enzyme, acid, and biomass yields when compared with other bacterial probiotics and an antibiotic. Moreover, X26 significantly improved the body weight of rats, highlighting its potential for industrial development as a supplement for animals. To optimize the fermentation process of this bacterium, we adopted the response surface design. When X26 was cultured in a medium with 16.5 g/L maltose, 25.00 g/L yeast extract, and 3.5 g/L K2HPO4, the optimal yield was predicted to be 5.1 × 109 CFU/mL. Consistent with the prediction, the yield of X26 in a 500-mL flask culture was (5.12 ± 0.01) × 109 CFU/mL, and in a 30-L fermenter was (5.11 ± 0.02) × 109 CFU/mL, accounting for a 9.9-fold higher field than that with a basal medium before optimization. We further optimized the fermentation process in the 30-L and a 10-T fermenter, generating yields of (7.8 ± 0.2) × 109 CFU/mL (spore rate: 96.54%) and (8.7 ± 0.1) × 109 CFU/mL (spore rate: 97.93%), respectively. These yields and spore rates were achieved at 45-55°C, the typical fermentation temperature of B. coagulans. Our findings indicate that B. coagulans X26 is a promising probiotic with considerable potential for cost-effective industrial fermentation.