Photodynamic inactivation of pathogenic bacteria using chlorogenic acid and UV-A (365 nm) irradiation

This study explored the antimicrobial efficacy and mechanism of a combined treatment using chlorogenic acid (CGA) and UV-A (365 nm) irradiation against four major foodborne pathogens-Escherichia coli O157:H7, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus-in both buffer and acidic beverage matrices. The CGA + UVA treatment showed strong bactericidal effects, particularly in green plum juice, where complete inactivation of L. monocytogenes was achieved (> 8-log reduction). Mechanistic investigations revealed that the CGA + UVA combination induced membrane depolarization, ATP depletion, and lipid peroxidation, ultimately leading to cell death. Importantly, the extent of sublethal injury differed between Gram-negative and Gram-positive bacteria, with Gram-negative strains more likely to survive in an injured state. Transmission electron microscopy confirmed that this pattern was linked to differences in cell envelope architecture-particularly the presence or absence of an outer membrane. The treatment caused minimal changes in juice quality, maintaining color, pH, and antioxidant properties. This study could provide a crucial bridge connecting fundamental discoveries to practical food safety applications, and by validating the efficacy across various pathogenic bacteria and food matrices, demonstrates the feasibility of CGA + UVA combination treatment for commercial implementation.