Antibacterial Effect and Mechanism of Melanin-Like/Zinc Oxide Nanocomposite on Pseudomonas fluorescens with Strong Spoilage Ability Isolated from Chilled Meat

To explore a packaging technology for chilled meat, this study developed a novel antibacterial nanomaterial, surface-modified zinc oxide nanoparticles using melanin nanoparticles as carriers (ZnO NPs@MelNPs) and evaluated its inhibitory effect on Pseudomonas fluorescens S_2-214, a strain with strong spoilage ability in chilled meat. Moreover, its antimicrobial mechanism was elucidated. The results demonstrated that ZnO NPs@MelNPs exhibited potent antibacterial activity, with a minimal inhibitory concentration (MIC) of 1.6 mg/mL against P. fluorescens S_2-214. Scanning electron microscopy (SEM) revealed that at this concentration, ZnO NPs@MelNPs caused physical damage to and significant morphological alterations in bacterial cells. Furthermore, analyses of relative cellular electrical conductivity, residual intracellular sodium (Na⁺) and magnesium (Mg²⁺) ion levels, and nucleic acid and protein leakage indicated the prepared nanomaterial disrupted the integrity of the cell membrane through physical damage, leading to increased membrane permeability and thereby the efflux of intracellular electrolytes and biomacromolecules, ultimately exerting an antibacterial effect.