Probiotic characteristics and safety evaluation of acid-tolerant lactic acid bacteria isolated from Suancai, a popular fermented vegetable in Northeast China.

This study aimed to isolate acid-tolerant lactic acid bacteria from Suancai, a traditional Chinese fermented vegetable, and evaluate their potential and safety as candidate probiotics. Fifteen dominant lactic acid bacteria strains were isolated from spontaneously fermented Suancai, and four isolates were selected based on their tolerance to acid and bile, as well as their autoaggregation, coaggregation, cell surface hydrophobicity, and adhesion capabilities. Based on 16S rRNA and pheS gene sequence analyses, the four strains were identified as Lactiplantibacillus plantarum (strain S5) and Levilactobacillus brevis (strains S1, H1, and H2). These strains were further evaluated for multiple in vitro probiotic properties. All four exhibited cholesterol removal capacity, DPPH and hydroxyl radical scavenging activity, gamma-aminobutyric acid production, and nitrite degradation ability. α-Glucosidase inhibitory activity was observed in three strains, with the exception of Levilactobacillus brevis S1. Additionally, all strains displayed antimicrobial activity against Escherichia coli, Staphylococcus aureus, and Salmonella paratyphi B. Safety assessment revealed that the strains were sensitive to ampicillin, erythromycin, and penicillin, resistant to gentamycin, and negative for indole production and hemolytic activity. In conclusion, the four selected strains demonstrated favorable probiotic characteristics and safety profile, supporting their potential as candidate probiotics for functional food application.