Optimization of High-density Cultivation Process and Investigation of Fermentation Characteristics of Lactiplantibacillus plantarum

Abstract:

[Objective] The conventional probiotic cultivation techniques suffer from problems such as low fermentation density, long cycles, and weak stress resistance, this study aimed to optimize the probiotic fermentation process, increase bacterial density, and enhance strain stress resistance.[Method] Lactiplantibacillus plantarum (L. plantarum) FMBL L23251 FJX was used for high-density fermentation. The fermentation process was optimized through single-factor experiments combined with response surface methodology. On this basis, the metabolic characteristics and the stress resistance of the prepared bacterial powder were further characterized. [Result] Under the malt extract-liquid ratio of 250 g∶1 L, yeast extract addition of 40 g/L, anhydrous sodium acetate addition of 6 g/L, galactooligosaccharide addition of 14 g/L, inoculum volume fraction of 6%, rotation speed of 100 r/min, pH 6.5, and fermentation at 37 ℃ for 24 h, the viable cell counts of L. plantarum FMBL L23251 FJX in the fermentation broth and freeze-dried powder reached 2.33×10¹² CFU/mL and 3.56×10¹³ CFU/g, respectively. The survival rate of L. plantarum FMBL L23251 FJX in the simulated gastrointestinal fluid was 76.75%. Compared with that in the MRS medium, L. plantarum FMBL L23251 FJX in barley malt wort medium showed increases of 19.93%, 29.26%, 25.19%, and 29.32% in scavenging rates against ABTS⁺, DPPH, hydroxyl, and superoxide anion free radicals, respectively. In addition, the mass concentration of total phenols and total flavonoids increased by 51.96% and 30.66%, respectively, while the total mass concentration of organic acids, short-chain fatty acids, and amino acids increased by 99%, 89%, and 48%, respectively. [Conclusion] This study provides data support for the large-scale application of locally sourced probiotics in food processing, biomedicine, and other fields.