Ultraviolet Light-Emitting Diode (UV-LED) Sterilization of Citrus Bacterial Canker Disease Targeted for Effective Decontamination of Citrus Sudachi Fruit.

A kind of citrus fruit with special flavor, Citrus sudachi harvested in Japan, are exported to various countries. However, the Citrus sudachi needs to be sterilized using aqueous solution of sodium hypochlorite because there is a possibility of the adhesion of citrus bacterial canker (CBC) which is not found in Europe. Due to the sterilization with time-consuming work, a more effective decontamination technique is required. A decontamination method using ultraviolet (UV) light irradiation is thus anticipated. Especially, the use of light emitting diodes (LEDs) wi UV light has many advantages in terms of energy consumption, lifetime, and compactness； although an appropriate method is yet to be established. In this study, we evaluate the fundamental effectiveness of UV-LED decontamination on the basis of the bactericidal ability on CBC in petri dishes, using six kinds of UV-LEDs (265, 280, 285, 300, 310, and 365 nm) . For each irradiation, the resultant bactericidal abilities (BAs) were evaluated precisely taking into account the differences in their optical absorptions. In addition, BAs per unit photon number were also estimated, as a fundamental wavelength-dependence of BA. As a result, the effectiveness of UV-LED irradiation with relatively short wavelengths was demonstrated clearly.