In order to increase the proliferation concentration of Lactobacillus fermentum, the high-density fermentation medium composition and cultivation technology were optimized to increase the number of viable counts. The results showed that peptone of yeast powder composite macromolecular peptide was the most suitable nitrogen source for L. fermentum, and saline buffer had no effect on the growth of the strain during constant pH culture. Both Mn2+ and Mg2+ were the limiting trace elements of L. fermentum. In addition, the accumulation of acid anions under neutral conditions did not have specific toxic effects on L. fermentum, and the growth of L. fermentum was mainly inhibited by osmotic pressure. The carbon-nitrogen consumption ratio when the growth rate was inhibited was used as the ratio of the carbon and nitrogen source in the medium, and the concentration of the carbon and nitrogen source was determined based on the osmotic pressure when the growth rate of the strain was inhibited. The constant pH batch cultivation and constant pH automatic feedback sugar supplement cultivation process to obtain the optimal cultivation strategy for each strain were further optimized: L. fermentum FXJCJ6-1, L. fermentum FGDLZR161, L. fermentum CCFM422 at constant pH 6.0, 5.5, 5.5, respectively. In batch culture, the number of viable counts reached (1.3±0.1)×1010, (1.1±0.1)×1010 and (9.5±0.5)×109 CFU/mL, respectively. Compared with MRS static culture, the number of viable counts increased by 3.1, 3.8 and 4.6 times, respectively. The application of the research results would significantly improve the industrial production efficiency of L. fermentum.
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