Optimization of Cultivation Conditions of Saccharomyces boulardii Against Diarrhea Using Response Surface Method

The fermentation medium and conditions of Saccharomyces boulardii were optimized based on single-factor experiments and response surface method.Single-factor experiments were performed to select the optimal carbon source,nitrogen source and inorganic salt.Response surface method was used to optimize the fermentation medium and conditions.A Plackett-Burman design was used to evaluate the effects of eight factors;the path of steepest ascent and the Box-Behnken design were performed for further optimization.The optimal fermentation medium contained 2% of maltose,2.08% of yeast extract,2% of glucose,with initial pH value of 6.0.The optimal fermentation conditions were as follows :5% inoculums added to 250 mL erlenmeyer flask with 29 mL medium volume were cultured with shaking speed 250 r/min at 29.6℃ for 24 h.In the optimal fermentation medium and conditions,the cell wet weight of Saccharomyces boulardii increased from 20.9 g/L to 32.2 g/L,increased by 54.1%,the number of viable yeast increased from 5.5×108CFU/mL to 8.3 ×108CFU/mL,increased by 50.9%.