Presentation Information
[21a-B201-2]Lifetime measurement of bactericidal species generated in water by oxygen radical irradiation
〇(M2)HiromiAlwi Yamamoto1, Naoyuki Iwata2, Masaru Hori3, Masafumi Ito1 (1.Meijo Univ., 2.Nagoya Univ., 3.Center for Low-Temperature Plasma Sciences)
Keywords:
bactericidal species,oxygen radical,escherichia coli
Recently, plasma-in-liquid sterilization has been attracted great attention. Several researchers reported that irradiation of atmospheric-pressure plasma to aqueous solutions produces short-lived bactericidal species such as hydroperoxyl radical (HOO•). However, effects of other species generated in plasma such as atomic oxygen (O•) to bacteria killing has not been widely discussed. In this study, we have measured lifetime of bactericidal species generated in water irradiated with oxygen radicals, and a Peltier device was used to control the temperature of the aqueous solution. DI water was irradiated with an oxygen-radical generator for 7 minutes at 0.5 ℃. After aging the irradiated samples for several ten secs, E. coli was suspended and incubated at 0.5 ℃ for 7 minutes. Then, survival numbers of E. coli were counted. From the results, the bactericidal effect decayed with increasing aging time, and the lifetime of the bactericidal species estimated to be 7.4 seconds at 0.5 ℃. Comparing to the reported half-life of HOO•, which is 74 minutes at 0 ℃, the bactericidal species in this study seems to be more unstable in water irradiated with oxygen radicals.