Structural and antibacterial mechanisms of the Lysozyme-chlorogenic acid complex against food pathogens

Lysozyme (LYS) and chlorogenic acid (CGA) are natural antibacterial compounds. In this study, we investigated the LYS-CGA colloid complex as a potential strategy to enhance antibacterial activity against Staphylococcus aureus and Salmonella typhimurium. A suite of spectroscopic techniques, including ultraviolet-visible absorption, fluorescence, and circular dichroism spectroscopy was employed to elucidate structural alterations in LYS upon CGA binding. The antibacterial effect was evaluated using a combination of methodologies, including the microbial assay, the scanning electron microscopy and flow cytometry. The binding of CGA induced a transition from α-helical to β-sheet structures in LYS, mediated by hydrogen bonding, hydrophobic, and Van der Waals interactions. This structure demonstrated synergistic antibacterial effect against S. aureus and S. typhimurium, resulting in a substantial reduction in minimum inhibitory concentrations. The complex disrupted bacterial cell membranes, causing leakage of nucleic acids and proteins. Finally, molecular docking was used to further decipher the interaction mechanism of the LYS-CGA complex. The present findings elucidate the structural basis and enhanced antibacterial activity of the LYS-CGA complex.