Synergistic action of ε-polylysine and theaflavin-3,3'-digallate against Hafnia alvei in turbot preservation: Quorum sensing disruption and bacterial sensitization

Overcoming the high-dose limitations of natural Preservatives like ε-polylysine (PL) is a pivotal challenge in food microbiology. This study explores a synergistic strategy combining PL with theaflavin-3,3'-digallate (TF3), a quorum sensing (QS) inhibitor, to control the spoilage bacterium Hafnia alvei H4. Our findings reveal a strong synergistic interaction (Fractional Inhibitory Concentration Index = 0.31), enabling a 50% reduction in the effective PL dosage. The underlying mechanism is multi-faceted: sub-inhibitory TF3 primarily disrupts QS-mediated virulence (e.g., biofilm formation, motility) and AHL signaling, as genetically validated using luxI and luxR knockout mutants, which critically sensitizes the Bacterial cells. This combined action culminates in a rapid, synergistic collapse of core physiological functions upon PL exposure. Critically, this synergy translates to practical efficacy: in turbot fillets, the TF3-PL combination extended shelf-life by over 3 days compared to PL alone, effectively suppressing microbial growth and spoilage metabolites while preserving sensory quality. This work establishes a "sensitization" strategy that leverages QS disruption to potentiate natural antimicrobials, offering a sustainable and resistance-mitigating approach for next-generation food preservation.