Research – Bacterial biofilm reduction by 275 and 455 nm light pulses emitted from light emitting diodes

Eradication of biofilms from the food contact surfaces is a challenging task, owing to their increased resistance to sanitizers and regular cleaning practices. The treatment with the light pulses emitted from the light emitting diode (LED) is an emerging surface decontamination technology, that can produce the antibiofilm effect by photodynamic inactivation. The objective of this study was to understand the antibiofilm efficacy of the 275 (Ultraviolet-C [UV-C]) and 455 nm (Blue) light pulses emitted from the LEDs against single and dual-species biofilms of Salmonella Typhimurium ATCC13311 and Aeromonas australiensis 03-09 on stainless steel (SS) coupons formed at different time. The biofilm formation by S. Typhimurium was improved when grown with A. australiensis in dual-species culture. Both 275 and 455 nm light pulses showed significant antibiofilm activity against S. Typhimurium and A. australiensis in single and dual-species biofilms. For instance, the 275 nm LED treatment of surfaces of SS coupons with 1.8 J/cm² dose on each surface, produced reductions of 4.24 and 3.9 log (CFU/cm²) in single (cell attachment) and dual-species biofilms of S. Typhimurium, and reductions of 4.45 and 4.99 log (CFU/cm²) in single and dual-species biofilms of A. australiensis. However, the susceptibility of A. australiensis toward 455 nm LED treatments was influenced by the presence of S. Typhimurium in the dual-species biofilm. The confocal laser scanning microscopy images revealed significant cell membrane damage in the dual-species biofilms by the LED treatments with 275 and 455 nm light pulses. Overall, several factors like surface temperature increase, strains used, treatment dose, treatment time, and incubation period of biofilms influenced the inactivation efficacy of the 275 and 455 nm LED treatments against the biofilms formed on SS coupons. This study provides an insight into the inactivation efficacy of LED light pulses against bacterial biofilms on food grade SS surfaces.