University of California

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

Andrea Cossu (Food Science and Technology Department, University of California - Davis, Davis, CA 95616 USA)Rohan V. Tikekar (Department of Nutrition and Food Science, University of Maryland - College Park, College Park, MD 20742 USA)Nitin Nitin (Food Science and Technology Department, University of California - Davis, Davis, CA 95616 USA) and (Department of Biological and Agricultural Engineering, University of California-Davis, Davis,CA 95616 USA)

Peroxides and chlorite based sanitizers are commonly used for washing procedures. Efficacy of these sanitizers is significantly reduced in the presence of organic content and may result in formation of harmful by-products. Therefore, new food grade sanitizers with enhanced antimicrobial efficacy are needed. In this work, we tested a new treatment for the sanitation of the wash-water based on the use of photosensitizers (PS) that continuously produce oxidative stress upon illumination. Antimicrobial effect of the food-grade PS dye Rose Bengal (RB) photosensitized with a visible light source on E. coli and bacteriophage T7 was evaluated. Effect of factors such as duration of illumination, growth phase of the microorganism and presence of organic matter on efficacy of inactivation was also studied. Data from exponential phase bacteria with high organic content (2,000 mg/L LB) showed that 10 µM and 100 µM RB achieved -1.83 ± 0.16 and -2.85 ± 0.05 logs reductions after 30 minutes and -5 and -6 logs reduction after 60 minute of illumination respectively. Stationary phase bacteria were more resistant than exponential phase bacteria since 10 µM RB achieved only a -3.96 ± 0.26 logs reduction after 60 minute of exposure. Experiments with T7 bacteriophage showed -3.58 ± 0.29 and -5 ± 0 logs reductions achieved in 30 minutes with 10 µM and 100 µM of RB respectively at 2,000 mg/L of LB. These results highlight the efficacy of RB as an antimicrobial against bacteria and viruses and demonstrate its potential as an alternative sanitizer for the food industry.

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