Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada; College of Biology and the Environment, Nanjing Forestry University, Nanjing 210037, China.
Department of Chemical and Biological Engineering, The University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada.
Water Res. 2019 Oct 15;163:114875. doi: 10.1016/j.watres.2019.114875. Epub 2019 Jul 16.
Recently, ultraviolet light-emitting diodes (UV-LEDs) have emerged as a new UV source, bringing flexibility for various UV wavelength combinations due to their unique feature of wavelength diversity. In this study, we investigated inactivation mechanisms of representative microorganisms at different wavelength combinations using UV-LEDs. Two types of indicator microorganisms were examined, namely Escherichia coli (E. coli) as a representative bacteria and bacteriophage MS2 as a representative virus. Different inactivation effects were observed, and the results for UVA pretreatment followed by UVC inactivation were particularly interesting. While a substantial shoulder in the E. coli UVC inactivation curve was observed, this was reduced by UVA pretreatment (365 nm) at 17 J/cm. Further, 52 J/cm UVA eliminated the shoulder in the fluence-response curves, resulting in improved UVC (265 nm) inactivation of E. coli by over two orders of magnitude. No inactivation improvement was observed for MS2. Moreover, UVA pretreatment eliminated photoreactivation of E. coli but did not affect dark repair. Detailed investigation of inactivation mechanisms revealed that hydroxyl radicals (•OH) played a significant role in the effects of UVA pretreatment. This study demonstrated that •OH radicals were generated inside E. coli cells during UVA pretreatment, which accounted for the subsequent effects on E. coli. The impact of UVA pretreatment on E. coli inactivation and reactivation was mainly due to increased levels of •OH radicals in E. coli cells, impairing cell functions such as DNA self-repair.
最近，紫外线发光二极管 (UV-LED) 作为一种新型的紫外光源出现，由于其波长多样性的独特特点，为各种紫外波长组合带来了灵活性。在本研究中，我们使用 UV-LED 研究了不同波长组合下代表性微生物的失活动力学。研究了两种类型的指示微生物，即作为代表性细菌的大肠杆菌 (E. coli) 和作为代表性病毒的噬菌体 MS2。观察到了不同的失活动效，UVA 预处理后再进行 UVC 灭活的结果尤其有趣。虽然在 E. coli 的 UVC 失活动力学曲线中观察到了一个很大的肩，但通过 UVA 预处理 (365nm) 在 17 J/cm 时减少了该肩。此外，52 J/cm 的 UVA 消除了剂量响应曲线中的肩，使大肠杆菌的 UVC (265nm) 灭活提高了两个数量级以上。对于 MS2 则没有观察到失活改善。此外，UVA 预处理消除了大肠杆菌的光复活，但没有影响暗修复。对失活动力学的详细研究表明，羟基自由基 (•OH) 在 UVA 预处理的效应中起重要作用。本研究表明，在 UVA 预处理期间，•OH 自由基在大肠杆菌细胞内生成，这解释了随后对大肠杆菌的影响。UVA 预处理对大肠杆菌失活和再激活的影响主要归因于大肠杆菌细胞中•OH 自由基水平的增加，破坏了细胞的功能，如 DNA 自我修复。
