Protecting bacteriophages under UV irradiation with brilliant blue FCF for targeted bacterial control

Compared to the standard methods for treating bacterial diseases, bacteriophages are eco-friendly and chemical-free. Exposure to ultraviolet (UV) light or sunlight hampers the efficacy of phage-based approaches. This is crucial when phages are <i>i)</i> exposed to sunlight (e.g., in agriculture) or <i>ii</i>) are to be used simultaneously with UV for sterilization. Here, we develop a method utilizing a food dye, brilliant blue FCF (BB), that selectively stabilizes bacteriophages against exposure to UV irradiation. In the absence of BB, all tested phages and bacteria are completely inactivated by UV exposure. However, with the addition of BB, all tested non-enveloped phages are effectively protected, while gram-negative bacteria remain vulnerable to UV inactivation. The mechanism of protection requires selective binding of BB to the virion. The simultaneous action of BB-stabilized bacteriophages and UV allows for the removal of up to 99.99 % of bacteria within only 30-60 min. We demonstrate the method's applicability in combating biofouling of membranes and food sterilization. We envision using the developed approach against biofouling in industrial processes, agriculture, and the food industry.