Figure 4.

(A) Response surface optimization results: carbon and nitrogen source response surface diagram (left), carbon source and buffer salt response surface diagram (middle), nitrogen source and buffer salt response surface diagram (right). (B) Comparison of growth curves before and after optimization (blue is optimal medium, red is MRS medium). (C) High-density fermentation process optimization results: fermenter constant pH optimization results (left), fermenter neutralizer optimization results (middle), high-density fermentation growth curve (right). Error bars represent standard error of the mean. The different letters above the bars in the figure indicate that there are significant differences between the data (p < 0.05).