Kojic acid and tea polyphenols inactivate Escherichia coli O157:H7 in vitro and on salmon fillets by inflicting damage on cell membrane and binding to genomic DNA

Summary The development of effective natural antibacterial agents is important due to the insecurity of synthetic antimicrobial agents and consumer preferences. In this study, kojic acid (KA) and tea polyphenols (TP) were found to exhibit synergistic inhibitory effect against Escherichia coli O157:H7 with a fractional inhibitory concentration index of 0.25. KA combined with TP at 25% of their minimum inhibitory concentrations (MICs) completely inactivated E. coli O157:H7 within 4 h. Subsequently, propidium iodide uptake tests, genomic DNA interaction analysis, molecular docking, field emission scanning electron microscopy and biofilm formation assay were conducted to understand the synergistic antibacterial mechanism of KA‐TP. The results demonstrated that KA‐TP attacked the cell membrane cooperatively, thus disturbing membrane integrity and cell structure, and KA could bind to the genomic DNA to affect the biofilm formation of E. coli O157:H7. Moreover, the contamination of E. coli O157:H7 on raw salmon fillets was eliminated to varying degrees after soaking treatments with KA and/or TP for 30 min. The depuration effect was further enhanced when KA combined with TP, and more than 2‐log reduction of E. coli O157:H7 was obtained under the treatment of KA‐TP at 2 MIC, suggesting that KA‐TP may serve as a natural compound disinfectant for ready‐to‐eat aquatic products.