Higher effectiveness of photoinactivation of bacterial spores, UV resistant vegetative bacteria and mold spores with 222 nm compared to 254 nm wavelength

Abstract

Eleven selected species of vegetative bacteria, bacteria spores and mold spores were irradiated with different doses of UV radiation of a 222 nm krypton-chloride excimer lamp and a 254 nm mercury lamp under laboratory conditions. Then the inactivation curves were determined. The necessary UV fluences for a respective reduction were higher for the excimer lamp for the tested vegetative bacteria of Bacillus cereus, Arthrobacter nicotinovorans, Staphylococcus aureus and Pseudomonas aeruginosa and slightly higher for the spores of Streptomyces griseus and Clostridium pasteurianum. However, less than 250 J/m 2 UV fluence with 222 nm was sufficient for a 4-log reduction, depending on the species. On the other hand, the UV fluences for the 254 nm mercury lamp were much higher for the bacterial spores of Bacillus cereus, Thermoactinomyces griseus and the bacteria of Deinococcus radiodurans and slightly higher for the mold spores of Aspergillus niger and Penicillium expansum. The results show that especially the germs with a higher UV resistance and those with more effective repair mechanisms can be inactivated more efficiently by the 222 nm excimer lamp. This may be due to the fact that low UV fluence mainly affects radiation sensitive microorganisms by DNA damage whereas at higher UV fluence (various) mechanisms of protein damage can presumably be held responsible for inactivation.

Sterilization effect of UV light on <I>Bacillus</I> spores using TiO2 films depends on wavelength

“…UVC enhanced the rate of inactivation by approximately 2 fold over that of UVB. Previous studies have reported that UV fluency primarily affects radiationsensitive microorganisms via DNA damage, whereas at higher UV fluency (various) mechanisms of protein damage are presumably responsible for inactivation (23).…”

Comparison of the Disinfection Effects of Vacuum‐UV (VUV) and UV Light on Bacillus subtilis Spores in Aqueous Suspensions at 172, 222 and 254 nm

“…(15), the ratio of inactivation rate constant at 222 nm to that at 254 nm is around 0.9, which is different from the value of 1.9 found in this study. Some other studies also showed higher disinfection efficiency of 222 nm UV light than that of 254 nm UV light (12,32). The discrepancy between the interpolated result and actual result is not clear.…”

“…It may be because the synergistic effect of UV absorption by DNA and triplet state energy transfer from DPA to DNA does not follow a linear relationship with UV wavelengths, or results from a more complex disinfection mechanism at 222 nm, which can enhance the efficiency of disinfection by UV light at this wavelength. For example, Clauβ (32) indicated that the higher disinfection efficiency at 222 nm can be found from the disinfection of microorganisms with higher UV resistance and more effective repair mechanisms, because some special proteins in these microorganisms, such as α / β ‐type SASP, can be damaged by 222 nm UV light more easily than by 254 nm UV light.…”

Inactivation of plant infecting fungal and viral pathogens to achieve biological containment in drainage water using UV treatment

“…However, the possibility already exists to increase the efficiency of the eradication further by modifying the UV treatment. For example, the addition of hydrogen peroxide or ozone during UV treatment, or the use of other oxidation technologies is under investigation (Clauss 2006;Bohrerova et al 2008;Sichel et al 2009). It seems likely that the UV treatment system described in this study could be adapted in the future to disinfect even higher densities of microbial populations that have accumulated in waste water.…”

“…Very limited data exist on UV inactivation dose rates or development of low‐energy waste water treatment systems for plant pathogens (Zhang and Tu 2000; Clauss 2006). Plant pathogenic microbes of agricultural importance increasingly investigated in research laboratories globally include the Ascomycete fungi, Fusarium graminearum (teleomorph Gibberella zeae ) and Fusarium culmorum which cause ear blight disease of small grain cereals, Mycosphaerella graminicola (anamorph Septoria tritici ) which causes Septoria leaf blotch disease of wheat, Magnaporthe oryzae the causal agent of rice blast disease, and the oilseed rape pathogens Leptosphaeria biglobosa and Leptosphaeria maculans.…”