Identification and characterization of a novel bacteriocin PFB252 from Bacillus velezensis with anti-methicillin-resistant Staphylococcus aureus and anti-biofilm activity for dairy food preservation

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) and its robust biofilm-forming capability pose severe threats to public health, livestock production, and food safety, and underscores the urgent need for novel antibacterial and anti-biofilm agents. In this study, we identified and characterized a novel bacteriocin, PFB252, derived from Bacillus velezensis through a multistep purification process involving acid precipitation, TA-GF75 gel column chromatography, Tiderose Q HP anion-exchange chromatography (TRUKING, Changsha, China), and reversed-phase HPLC. PFB252 exhibited remarkable thermal stability, pH tolerance, and resistance to enzymatic degradation, and demonstrated potent antibacterial activity against MRSA. At subinhibitory concentrations (1/32× minimum inhibitory concentration [MIC] and 1/16× MIC), PFB252 significantly disrupted biofilm formation and impaired the metabolic viability of embedded bacteria, and it drastically reduced extracellular polysaccharide, the key component of the biofilm matrix. Transcriptional analysis further revealed that PFB252 at subinhibitory concentrations downregulated critical biofilm-associated genes. PFB252 exhibited strong antimicrobial efficacy in dairy applications and could reduce MRSA counts in milk from 10³ to <10 cfu/mL within 4 d at MIC and maintain suppression in cheese below 10² cfu/g over 7 d. These properties highlight PFB252's potential as a natural biopreservative for combating MRSA in food systems and offer a promising solution for food safety applications.