Antibacterial mechanism of vitamin K3-mediated photodynamic inactivation against Pseudomonas fluorescens and its influences on blunt bream (Megalobrama amblycephala) quality

[Display omitted] •UV-A irradiation could improve the antimicrobial effect of Vitamin K3 (VK3).•VK3-mediated photodynamic inactivation (PDI) effectively inactivated P. fluorescens.•VK3-mediated PDI damaged membrane integrity, DNA and protein.•VK3-mediated PDI reduced P. fluorescens contamination on blunt bream.•VK3-mediated PDI was used to maintained quality on blunt bream. Photodynamic inactivation (PDI) has emerged as a novel non-thermal process technology for inactivating microorganisms due to its low cost, safety, and efficiency. This study aimed to investigate the antimicrobial effect of VK3-mediated PDI against Pseudomonas fluorescens (P. fluorescens) and to assess its impact on the quality of the blunt bream contaminated with P. fluorescens. The inhibition efficiency and photosensitization mechanism were investigated under different VK3 concentrations and UV-A light time conditions. The results showed that PDI could significantly inactivate P. fluorescens >7.0 log10 cfu/ml with 1 mM VK3 and 45 min of UV-A irradiation. Type I and type II photoresponses could co-occur in VK3-mediated PDI by quantitatively analyzing the photoresponse product ROS (OH, H2O2, 1O2). It was observed by SEM and TEM that the combined treatment of VK3 and UV-A disrupted the cellular integrity of P. fluorescens, leading to leakage of cell contents. Meanwhile, it degraded intracellular proteins and destroys genomic DNA, ultimately leading to bacterial death. In addition, the PDI system slowed down P. fluorescens’ proliferation during the blunt bream storage at 4 °C. The PDI system effectively killed 59 % of P. fluorescens on the blunt bream fillets under 1.5 mM VK3 and 60 min of UV-A irradiation. The VK3-mediated PDI delayed pH change and TVB-N production, inhibited protein degradation and fat oxidation, and ultimately maintained the quality of fish fillets. This study provides a promising PDI system for controlling food microbial contamination and maintaining the storage quality of aquatic products.