New water disinfection system using UVA light-emitting diodes.
OBJECTIVE
To evaluate the ability of high-energy ultraviolet A (UVA) light-emitting diode (LED) to inactivate bacteria in water and investigate the inactivating mechanism of UVA irradiation.


RESULTS
We developed a new disinfection device equipped with high-energy UVA-LED. Inactivation of bacteria was determined by colony-forming assay. Vibrio parahaemolyticus, enteropathogenic Escherichia coli, Staphylococcus aureus and Escherichia coli DH5alpha were reduced by greater than 5-log(10) stages within 75 min at 315 J cm(-2) of UVA. Salmonella enteritidis was reduced greater than 4-log(10) stages within 160 min at 672 J cm(-2) of UVA. The formation of 8-hydroxy-2'-deoxyguanosine in UVA-LED irradiated bacteria was 2.6-fold higher than that of UVC-irradiated bacteria at the same inactivation level. Addition of mannitol, a scavenger of hydroxyl radicals (OH(*)), or catalase, an enzyme scavenging hydrogen peroxide (H(2)O(2)) to bacterial suspensions significantly suppressed disinfection effect of UVA-LED.


CONCLUSIONS
This disinfection system has enough ability to inactivate bacteria and OH(*) and H(2)O(2) participates in the disinfection mechanism of UVA irradiation.


CONCLUSIONS
We newly developed UVA irradiation system and found that UVA alone was able to disinfect the water efficiently. This will become a useful disinfection system.
Department of Nutrition and Metabolism, Institute of Health Biosciences, The University of Tokushima Graduate School, Kuramoto-cho, Tokushima, Tokushima, Japan.
A
A
Hamamoto
M
M
Mori
A
A
Takahashi
M
M
Nakano
N
N
Wakikawa
M
M
Akutagawa
T
T
Ikehara
Y
Y
Nakaya
Y
Y
Kinouchi
D000975:Antioxidants / Q000494:pharmacology; D001419:Bacteria / Q000528:radiation effects*; D002374:Catalase / Q000494:pharmacology; D003114:Colony-Forming Units Assay; D004203:Disinfection; D054308:Enteropathogenic Escherichia coli / Q000528:radiation effects; D004926:Escherichia coli / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000037:antagonists & inhibitors; D017665:Hydroxyl Radical / Q000037:antagonists & inhibitors; D008353:Mannitol / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000528:radiation effects; D014466:Ultraviolet Rays; D014736:Vibrio parahaemolyticus / Q000528:radiation effects; D014871:Water Microbiology; D018508:Water Purification / Q000379:methods*
D000975:Antioxidants; D017665:Hydroxyl Radical; D008353:Mannitol; D006861:Hydrogen Peroxide; D002374:Catalase