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.