Screening of potential probiotic bifidobacteria from intestinal tract and its application in fermented milk

Bifidobacteria, a significant component of human gut microbiota, play a crucial role in maintaining human health. Studies have shown that the composition of gut microbiome is closely related to the geographical environment, ethnicity, and dietary structure of the host. Currently, most of the mainstream probiotics on the market are based on the gut microbiota characteristics of Western populations, which may not be completely suitable for the gut environment of Chinese people. Therefore, the isolation and screening of bifidobacteria with probiotic functions in the intestinal tract is critically important to meet the demands of the Chinese market. In the present study, 217 bifidobacterial strains were isolated and identified from 35 fecal samples collected from the city of Hohhot, Inner Mongolia, China. Further investigations were conducted to determine the probiotic potential of these strains. Among the screened strains, Bifidobacterium longum ssp. longum IMAU12449 was identified as the most promising probiotic strain. The survival rate of strain IMAU12449 was highest in the simulated artificial gastrointestinal fluid. The survival rate of strain IMAU12449 in artificial gastric fluid for 3 h was 62.38%, and the survival rate was 40.30% in the artificial intestinal fluid for 8 h. Furthermore, the strain exhibited excellent cell autoaggregation (72.79%) and surface hydrophobicity (45.66%). Strain IMAU12449 also exhibited a strong inhibitory effect on common pathogens. Safety evaluation revealed that the strain possessed 2 potential antibiotic resistance genes and no virulence factors. This strain exhibited γ-hemolysis in vitro. The advantages of a stable viable count, moderate acidity, and absence of whey precipitation were observed in fermented cow and soy milk processed by strain IMAU12449 combined with commercial starters. After storage at 4°C for 21 d, the viable cell count remained above 10⁷ cfu/mL. In conclusion, a bifidobacterial strain, IMAU12449, with favorable probiotic properties was identified in this study. This strain has demonstrated significant potential for application in fermented milk, and further research should be conducted to elucidate its role in promoting health.