Characterization of Lactococcus lactis ZB1 from traditional fermented bacon: Genomic insights and antifungal potential for food preservation

Lactococcus lactis strains from traditional fermented foods are important sources of both probiotic candidates and natural biopreservatives. In this study, L. lactis ZB1, isolated from Zhenba bacon (Shaanxi, China), was comprehensively characterized for its genomic features and antifungal activity. Genomic analysis revealed a genome size of 2.312 Mb with 2165 protein-coding genes, 64 tRNAs, and 19 rRNAs. Key genes associated with carbohydrate metabolism, stress resistance, and bacteriocin biosynthesis were identified, including a cluster encoding class IIc bacteriocin, suggesting probiotic potential and antimicrobial capacity. The cell-free supernatant (CFS) of ZB1 exhibited strong, concentration-dependent antifungal activity against food spoilage fungi (Penicillium griseofulvum Dierckx, Aspergillus ochraceus), achieving inhibition rates over 60 % at 40 % CFS concentration and above 90 % at 80 %. The antifungal effect remained highly stable following heat treatment. The inhibition activity was largely unchanged after treatment at 60 °C and 80 °C, and even after heating at 100 °C, the inhibition rate decreased by only about 10 %. In contrast, the activity was markedly reduced after pH neutralization, indicating that organic acids were the major active components. Protease treatment had little effect, further confirming the non-proteinaceous nature of the primary antifungal substances. These findings highlight L. lactis ZB1 as a promising probiotic strain and a thermally stable, organic acid–mediated natural preservative for improving the safety and shelf life of food products.