Isolation and characterization of Lactobacillus plantarum LP2301 from bovine milk: acid and bile tolerance, antibacterial activity, and genomic safety evaluation.

The long-term and non-standard use of antibiotics poses a significant threat to food safety and human health. Probiotics are a promising alternative to antibiotics, effectively combating bacterial infections while reducing the risks associated with antibiotic resistance. Gram staining confirmed LP2301 as a Gram-positive bacterium, and species identification as Lactobacillus plantarum was established by 16S rRNA gene sequencing and whole-genome sequencing. In this study, LP2301 was isolated from the milk of a healthy dairy cow, which exhibits characteristics of acid (pH = 2.5) and 0.3% bile salt tolerance and the ability to secrete effective substances that inhibit the growth of pathogenic bacteria. Through whole-genome sequencing, we identified plantaricin biosynthetic gene clusters (including plnE and plnF) and the absence of hemolytic ability in LP2301. Combined experimental and genomic evidence suggests that the antimicrobial activity is attributable to bacteriocins, particularly plantaricin-related peptides, and Proteinase K treatment experiment confirmed the presence of proteinaceous bacteriocin-like substances contributing to antimicrobial activity. However, the specific effective components require further experimental verification. These findings suggest that LP2301 has potential as a natural antimicrobial agent and a candidate for further evaluation as an antibiotic alternative, pending in vivo validation.