Antimicrobial effect of photosensitized Rose Bengal on bacteria and viruses in model wash water

Peroxides and chlorite-based sanitizers are commonly used for washing procedures. The efficacy of these sanitizers is significantly reduced in the presence of organic content and may result in the formation of harmful secondary products. Therefore, new food-grade sanitizers with enhanced antimicrobial efficacy are needed. In this work, we tested a visible light-activated photosensitizer, Rose Bengal (RB), for the reduction of microbial load in simulated wash water. Escherichia coli BL21 and bacteriophage T7 were selected as model bacterial and viral targets, respectively. Effects of duration of illumination, growth phase of the bacterium, and the presence of organic matter on efficacy of inactivation were evaluated. Photosensitized RB was able to achieve 6 log colony-forming units (CFU)/mL reduction in the exponential-phase bacteria in the presence of high organic content (2000 ppm LB broth) within 45 min of treatment. The results also demonstrated that the stationary-phase microbes were significantly more resistant to photoinactivation as compared to the exponential-phase microbes at both low and high organic loads (200 and 2000 ppm). The results indicate that RB dye can be internalized in bacteria and induces damage to the cell membrane upon photoactivation. Viral inactivation studies demonstrated that photoactivation of RB can achieve 5 log PFU/mL reduction in viral load in the presence of 2000 ppm LB after 30 min of treatment. Overall, these results highlight the efficacy of RB as an antimicrobial against bacteria and viruses in simulated wash water and demonstrate its potential as an alternative sanitizer for the food industry.