Fermentation process optimization of a bacteriostatic Bacillus coagulans based on response surface methodology

Bacillus coagulans is a spore-producing lactic acid bacterium with strong stress resistance. It has been widely used in food preservation, food fermentation, livestock diarrhea prevention, medication-assisted treatment, pollutant removal et al. In the study, a Bacillus coagulans strain with superior inhibition on Staphylococcus aureus, Escherichia coli, Vibrio parahaemolyticus and Aeromonas hydrophila was screened. Its medium composition and culture conditions were optimized in flasks using single factor experiment, Plackett Burman experiment, minimum addition experiment and response surface analysis experiment. The optimal medium composition was determined to be 14.64 g/L molasses, 0.4848 g/L MgSO₄, 0.0833 g/L MnSO₄, 1.5 g/L K₂HPO₄, 0.5 g/L KCl, 8 g/L peptone, and 10 g/L corn syrup dry powder. The optimal culture conditions were 40 °C, initial pH 6.0, inoculation ratio 4%, loading ratio 30%, and rotational speed 140 rpm, and cultivate for 44 h. After feed strategy optimization in 10 L fermenting tank, the concentrations of live bacteria and spores reached 4.63 × 10⁹ CFU/mL and 4.03 × 10⁹ CFU/mL, corresponding to a 14.5-fold and 16.4-fold increase, respectively. This study reduced the production cost of Bacillus coagulans greatly and supply technical support for Bacillus coagulans production.