The "One-Two Punch": A conceptual analysis of nisin and lysozyme synergy against Listeria monocytogenes biofilms and their dependence on environmental factors.

AIMS: The persistence of Listeria monocytogenes biofilms in food processing environments poses a significant challenge to food safety, as these resilient communities exhibit high tolerance to conventional sanitation. This conceptual review synthesises current literature on two natural antimicrobials: nisin and lysozyme, to evaluate their combined potential against L. monocytogenes biofilms and to propose a novel "One-Two Punch" model describing their sequential synergistic action. It further examines how environmental factors, including surface physicochemical properties, biofilm maturity, and hydrodynamic conditions, may influence the effectiveness of this strategy. METHODS AND RESULTS: Through a comprehensive synthesis of existing literature on antimicrobial mechanisms and biofilm physiology, a theoretical framework for combined antimicrobial action was developed. Established findings confirm that lysozyme hydrolyses the peptidoglycan layer of Gram-positive cell walls, while nisin binds to lipid II to induce cytoplasmic membrane pore formation. As a novel conceptual contribution, this review proposes that, when applied in combination, these agents operate through a complementary, stepwise mechanism: lysozyme-mediated peptidoglycan hydrolysis of peripheral biofilm cells enhances subsequent nisin penetration to the cytoplasmic membrane of target cells, achieving greater bactericidal efficacy than either agent alone. Environmental variables, including surface material, biofilm age, and hydrodynamic conditions, emerge as key determinants of biofilm architecture and antimicrobial susceptibility. CONCLUSIONS: The "One-Two Punch" model provides a mechanistically grounded framework for combining natural antimicrobials to target resilient L. monocytogenes biofilms. Key environmental constraints, critical knowledge gaps, and directions for experimental validation are outlined, providing a foundation for designing more effective biofilm control strategies across diverse food industry settings.