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Effects of UV Irradiation by Light Emitting Diodes on Heterotrophic Bacteria in Tap Water
Author(s) -
Oguma Kumiko,
Kanazawa Kaori,
Kasuga Ikuro,
Takizawa Satoshi
Publication year - 2018
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12891
Subject(s) - heterotroph , methylobacterium , ultraviolet , tap water , bacteria , 16s ribosomal rna , food science , biology , chemistry , materials science , environmental science , optoelectronics , environmental engineering , genetics
Ultraviolet light emitting diodes ( UV ‐ LED s) are small mercury‐free devices that can be installed at the point of use ( POU ) of water for disinfection. Considering that heterotrophic bacteria are of concern in drinking water systems, we applied a flow‐through UV ‐ LED apparatus to dechlorinated tap water, and determined the heterotrophic plate count ( HPC ) in samples after UV ‐ LED exposure ( UV +) compared to samples without UV ‐ LED application ( UV −). The UV + and UV − samples were maintained at 20°C to track HPC profiles during storage for 7 days. It was confirmed that UV + samples showed negative HPC or lower HPC than UV − for 5 days of storage after the flow‐through test. HPC bacteria formed colonies with different morphological characteristics, and yellow colonies were closest to Novosphingobium sp., with 99% identity, while white and pale pink colonies were closest to Methylobacterium sp., with 99–100% identity, based on 16S rRNA gene sequences. White colonies became dominant in UV +, indicating that UV ‐ LED exposure can select UV ‐resistant species such as Methylobacterium . This study shows the effects of UV ‐ LED application on HPC bacteria in tap water and implies that future research is required on the significance and impacts of microbial selection by UV ‐ LED exposure.