The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivatio...The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivation of Escherichia coli(E.coli) and Enterococcus faecalis(E.faecalis) in secondary effluents which were disinfected respectively by pure UV and UV-TiO_2 was investigated.The results show that the disinfection efficiency of UV-TiO_2 is much higher than that of the pure UV disinfection.The photoreactivation rate of E.coli is much higher in pure UV disinfection than in UV-TiO_2 photocatalytic disinfection.Under high light intensity in UV-TiO_2 disinfection,high resurrection rate can be induced.However,a higher resurrection rate can be introduced even under low light intensity in pure UV disinfection alone.Meanwhile,UV-TiO_2 disinfection has a strong inhibition effect on E.faecalis photoreactivation.When the light intensity is lower than 21 μW/cm^2,nearly no resurrection of E.faecalis occurs after 72 h resurrection irradiation,and a little resurrection rate is observed only under a strong photoreactivating light intensity.展开更多
Sunlight has an indispensable importance for living things in nature[1-3].However,the direct absorption of UV will lead to the formation of pyrimidine dimers between adjacent pyrimidines in DNA strands usually in the ...Sunlight has an indispensable importance for living things in nature[1-3].However,the direct absorption of UV will lead to the formation of pyrimidine dimers between adjacent pyrimidines in DNA strands usually in the form of cyclobutene pyrimidine dimers(CPDs)and pyrimidine(6-4)pyrimidone photoproducts(6-4PPs)which causes great damage[4-6].A DNA repair system,known as photoreactivation,can effectively repair the dimers using photolyase[7-9],which has currently been found in plants,prokaryotic and eukaryotic cells[10-12].This study was carried out to determine whether photolyase DNA repair can be observed in yeast.Several yeast Petri dishes were treated with ultraviolet radiation,different treatments were then added to them,and the colonies were counted after culturing,hence verifying that yeasts can use the photoreactivation process.展开更多
Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity ...Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm2 for E. coli DH5ct, and 23 mJ/cm2 for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm2 of UV and low concentration of chlorine （1.5 mg/L） could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH3-N concentration.展开更多
The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has be...The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has been studied. This article briefly recounts the early history of this field.展开更多
Ultraviolet(UV)/monochloramine(NHCl) as an advanced oxidation process was firstly applied for Aspergillus spores inactivation. This study aims to: i) clarify the inactivation and photoreactivation characteristics of U...Ultraviolet(UV)/monochloramine(NHCl) as an advanced oxidation process was firstly applied for Aspergillus spores inactivation. This study aims to: i) clarify the inactivation and photoreactivation characteristics of UV/NHCl process, ii) compared with UV/Clin inactivation efficiency, photoreactivation and energy consumption. The results illustrated that UV/NHCl showed better inactivation efficiency than that of UV alone and UV/Cl, and could effectively control the photoreactivation. For instance, the inactivation rates for Aspergillus flavus, Aspergillus niger and Aspergillus fumigatus in the processes of UV/NHCl(2.0 mg/L) was 0.034, 0.030 and 0.061 cm^(2)/m J), respectively, which were higher than that of UV alone(0.027, 0.026 and 0.024 cm^(2)/m J) and UV/Cl(0.023, 0.026 and 0.031 cm^(2)/m J). However, there was no synergistic effect for Aspergillus flavus and Aspergillus fumigatus. As for Aspergillus niger, the best synergistic effect can reach 1.86-log 10. This may be due to their different resistance to disinfectants, which were related to the size, an outer layer of rodlets(hydrophobins) and pigments. After UV/NHCl inactivation, the degree of cell membrane damage and intracellular reactive oxygen species were higher than that of UV alone. UV/NHCl had the advantages of high inactivation efficiency and inhibition of photoreactivation, which provides a new entry point for the disinfection of waterborne fungi.展开更多
The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfectio...The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone （UV/ozone） coexposure and sequential UV-followed-by-ozone （UV- ozone） and ozone-followed-by-UV （ozone-UV） expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water.展开更多
Utilizing a pulse radiolysis equipment with time-resolved optical detector, kinetic processes of electron-induced splitting of cis-syn 1,3-dimethyluracil cyclobutane dimer (DMUD) in aqueous solution were investigated ...Utilizing a pulse radiolysis equipment with time-resolved optical detector, kinetic processes of electron-induced splitting of cis-syn 1,3-dimethyluracil cyclobutane dimer (DMUD) in aqueous solution were investigated in the presence or absence of riboflavin (RF) or flavin adenine dinucleotide (FAD). It has been observed that the cyclobutane pyrimidine dimer reacting with hydrated electron splits spontaneously to give a monomer and a monomer radical anion, and the anion transfers one electron to RF or FAD. From the buildup kinetics of radical species, the rate constants of electron transfer from the monomer radical anion to RF and FAD have been determined. On the basis of comparison of the interactions between DMUD and hydrated electron in the presence and absence of RF or FAD, a chain reaction process in the absence of RF or FAD has been demonstrated.展开更多
基金Projects(51174090,51168026)supported by the National Natural Science Foundation of China
文摘The disinfected bacteria will be a photoreactivation under the irradiation of the sunlight,and the light intensity plays an important role in the bacteria resurrection.The effect of light intensity on photoreactivation of Escherichia coli(E.coli) and Enterococcus faecalis(E.faecalis) in secondary effluents which were disinfected respectively by pure UV and UV-TiO_2 was investigated.The results show that the disinfection efficiency of UV-TiO_2 is much higher than that of the pure UV disinfection.The photoreactivation rate of E.coli is much higher in pure UV disinfection than in UV-TiO_2 photocatalytic disinfection.Under high light intensity in UV-TiO_2 disinfection,high resurrection rate can be induced.However,a higher resurrection rate can be introduced even under low light intensity in pure UV disinfection alone.Meanwhile,UV-TiO_2 disinfection has a strong inhibition effect on E.faecalis photoreactivation.When the light intensity is lower than 21 μW/cm^2,nearly no resurrection of E.faecalis occurs after 72 h resurrection irradiation,and a little resurrection rate is observed only under a strong photoreactivating light intensity.
文摘Sunlight has an indispensable importance for living things in nature[1-3].However,the direct absorption of UV will lead to the formation of pyrimidine dimers between adjacent pyrimidines in DNA strands usually in the form of cyclobutene pyrimidine dimers(CPDs)and pyrimidine(6-4)pyrimidone photoproducts(6-4PPs)which causes great damage[4-6].A DNA repair system,known as photoreactivation,can effectively repair the dimers using photolyase[7-9],which has currently been found in plants,prokaryotic and eukaryotic cells[10-12].This study was carried out to determine whether photolyase DNA repair can be observed in yeast.Several yeast Petri dishes were treated with ultraviolet radiation,different treatments were then added to them,and the colonies were counted after culturing,hence verifying that yeasts can use the photoreactivation process.
基金supported by the National Major Project of Science & Technology Ministry of China (No. 2008ZX07314-003,2009ZX07424-003)the National HiTech Research and Development Program (863) of China (No. 2008AA062501,2008AA06A414)
文摘Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm2 for E. coli DH5ct, and 23 mJ/cm2 for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm2 of UV and low concentration of chlorine （1.5 mg/L） could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH3-N concentration.
文摘The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has been studied. This article briefly recounts the early history of this field.
基金supported by the Natural Science Foundation of China (Nos. 51978557 , 51678472)the Shaanxi Science Fund for Distinguished Young Scholars (No. 2018JC026)+1 种基金the Youth Innovation Team of Shaanxi UniversitiesShaanxi Provincial Key Research and Development Project (No. 2020ZDLSF06-05)。
文摘Ultraviolet(UV)/monochloramine(NHCl) as an advanced oxidation process was firstly applied for Aspergillus spores inactivation. This study aims to: i) clarify the inactivation and photoreactivation characteristics of UV/NHCl process, ii) compared with UV/Clin inactivation efficiency, photoreactivation and energy consumption. The results illustrated that UV/NHCl showed better inactivation efficiency than that of UV alone and UV/Cl, and could effectively control the photoreactivation. For instance, the inactivation rates for Aspergillus flavus, Aspergillus niger and Aspergillus fumigatus in the processes of UV/NHCl(2.0 mg/L) was 0.034, 0.030 and 0.061 cm^(2)/m J), respectively, which were higher than that of UV alone(0.027, 0.026 and 0.024 cm^(2)/m J) and UV/Cl(0.023, 0.026 and 0.031 cm^(2)/m J). However, there was no synergistic effect for Aspergillus flavus and Aspergillus fumigatus. As for Aspergillus niger, the best synergistic effect can reach 1.86-log 10. This may be due to their different resistance to disinfectants, which were related to the size, an outer layer of rodlets(hydrophobins) and pigments. After UV/NHCl inactivation, the degree of cell membrane damage and intracellular reactive oxygen species were higher than that of UV alone. UV/NHCl had the advantages of high inactivation efficiency and inhibition of photoreactivation, which provides a new entry point for the disinfection of waterborne fungi.
基金We acknowledge the financial support from the National Natural Science Foundation of China （Grant No. 51108117） and the Hong Kong Innovation and Technology Fund （No. ITS/336/09）.
文摘The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone （UV/ozone） coexposure and sequential UV-followed-by-ozone （UV- ozone） and ozone-followed-by-UV （ozone-UV） expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water.
基金This work was supported by the National Natural Science Foundation of China(Grant No.30000036)Special Fund for Doctoral Program fromthe Ministry of Education of China and Foundation of University of Science and Technology of China.
文摘Utilizing a pulse radiolysis equipment with time-resolved optical detector, kinetic processes of electron-induced splitting of cis-syn 1,3-dimethyluracil cyclobutane dimer (DMUD) in aqueous solution were investigated in the presence or absence of riboflavin (RF) or flavin adenine dinucleotide (FAD). It has been observed that the cyclobutane pyrimidine dimer reacting with hydrated electron splits spontaneously to give a monomer and a monomer radical anion, and the anion transfers one electron to RF or FAD. From the buildup kinetics of radical species, the rate constants of electron transfer from the monomer radical anion to RF and FAD have been determined. On the basis of comparison of the interactions between DMUD and hydrated electron in the presence and absence of RF or FAD, a chain reaction process in the absence of RF or FAD has been demonstrated.
