New Horizons in Microbiological Food Safety: Ultraefficient Photodynamic Inactivation Based on a Gallic Acid Derivative and UV-A Light and Its Application with Electrospun Cyclodextrin Nanofibers

An excellent bactericidal effect of octyl gallate (OG)-mediated photodynamic inactivation (PDI) against foodborne pathogens (Escherichia coli and Staphylococcus aureus) was evaluated in relation to the mode of action. UV-A irradiation (wavelength, 365 nm; irradiance, 8.254 ± 0.18 mW/cm2) of the bacterial suspension containing 0.15 mM OG could lead to a >5-log reduction of viable cell counts within 30 min for E. coli and only 5 min for S. aureus. Reactive oxygen species (ROS) formation was considered the main reason for the bactericidal effect of OG + UV-A light treatment because toxic ROS induced by OG-mediated PDI could attack the cellular wall, proteins, and DNA of microbes. Moreover, the bactericidal effect, as well as the yields of ROS, depended on OG concentrations, irradiation time, and laser output power. Furthermore, we prepared an edible photodynamic antimicrobial membrane comprising electrospun cyclodextrin nanofibers (NFs) by embedding OG. The resultant OG/HPβCD NFs (273.6 μg/mL) under UV-A irradiation for 30 min (14.58 J/cm) could cause a great reduction (>5-log) of viable bacterial counts of E. coli. The in situ photodynamic antibacterial activity of OG/HPβCD NF-based packaging was evaluated during the Chinese giant salamander storage. Overall, this research highlights the dual functionalities (antibacterial and photodynamic properties) of OG as both an antibacterial agent and photosensitizer and the effectiveness of electrospun NFs containing OG as an active antibacterial packaging material for food preservation upon UV light illumination.