UV‐A Light‐Enhanced Antibacterial Activity of Lactobionic Acid Against Staphylococcus aureus and Escherichia coli Strains

Lactobionic acid (LBA) is increasingly used for its multiple properties, including preservative and prebiotic effects. With the aim of enhancing its antimicrobial efficacy, this study explores its interaction with sublethal levels of ultraviolet‐A (UV‐A) light to combat foodborne bacteria. The antibacterial effect of the acid against Staphylococcus aureus IPLA1, S. aureus CECT 240, and Escherichia coli CECT 101 was first assessed by microdilution assays. The three strains are sensitive to the acid, and for all of them, the minimum inhibitory concentrations (MICs) were lower than the minimum bactericidal concentration (25 mg/mL). UV‐A light induced a reversible inactivation, but it significantly enhanced the efficacy of LBA. Furthermore, flow cytometry analysis revealed that treating cells simultaneously with LBA and UV‐A altered membrane permeability and affected esterase activity. The effect of the tested agents on the morphological structure was verified by scanning electron microscopy, and the images show structural deformation and cell clumps. The antimicrobial potential of the starch‐based film enriched with LBA at 1/2 and 1 MIC was demonstrated in broth culture medium, and UV‐A treatment enhanced its effectivity. Regarding the application in food, the produced films were effective for microbial preservation of cheese slices under refrigerated storage conditions, whereas simultaneous application of UV‐A with LBA‐films achieved complete elimination of the bacteria. Overall, this research highlights the effectiveness of the combined LBA–UV‐A treatment in controlling bacterial proliferation in food.