Development of a standard evaluation method for microbial UV sensitivity using light-emitting diodes

Area of Science:

• Microbiology
• Photochemistry
• Biotechnology

Background:

• Ultraviolet (UV) light is a proven disinfection method.
• UV light-emitting diodes (UV-LEDs) offer versatile applications due to their compact size and tunable wavelengths.
• Standardized experimental conditions for evaluating UV-LED efficacy against microorganisms are lacking.

Purpose of the Study:

• To develop and validate a standardized UV-LED irradiation system for evaluating microbial UV sensitivity.
• To establish precise irradiation conditions for reproducible UV disinfection studies.
• To assess the UV sensitivity of *Escherichia coli* across a range of UV-LED wavelengths.

Main Methods:

• Development of a novel UV-LED device with strictly controlled irradiation parameters (250-365 nm).
• Consideration of accurate irradiance, spectra, uniformity, dose, beam angle, reflections, and sample conditions.
• Evaluation of *E. coli* inactivation using the standardized system and U280 LED as a reference.

Main Results:

• Established standard irradiation conditions: 1 mW/cm² irradiance, 10x diluted A600=0.5 bacterial solution, 1 mL volume, 100 mm working distance.
• Quantified *E. coli* inactivation at 267 nm, showing a peak sensitivity.
• Demonstrated a significant wavelength-dependent inactivation effect for UV-LEDs.

Conclusions:

• The developed UV-LED irradiation system is validated for standardized microbial disinfection research.
• This standardized method can contribute to improved food/water hygiene and infectious disease prevention equipment.
• Understanding wavelength-specific UV sensitivity is crucial for optimizing disinfection strategies.