Response surface methodology can be used to predict photoinactivation of foodborne pathogens using Rose Bengal excited by 530 nm LED

In this work, the photodynamic bactericidal effect of Rose Bengal (RB), combined with green LED light, against Staphylococcus aureus and Salmonella Typhimurium, was investigated. The interaction of RB concentration and illumination time was evaluated using a response surface methodology, and a second-order polynomial empirical model was adjusted to the experimental data. The derived model predicted the combined influences of these factors on S. aureus and S. Typhimurium counts, in accordance with predictions and experimental observations (R-2 = 0.8483 and p = .0013 for S. aureus; R-2 = 0.9191 and p = .0001 for S. Typhimurium). Total inhibition of S. aureus and S. Typhimurium was observed when applying a light dose of 0.125 J cm(-2) and 152.0 J cm(-2), respectively. The treatments also showed loss of membrane integrity, morphological changes, and internal cell structural alterations. In sum, the polynomial model developed could provide accurate information on the combined influences of RB and green LED light in aPDT treatment and, that this combination was able to inactivate S. aureus and S. Typhimurium.