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Polyzois A, Kirilovsky D, Dufat TH, Michel S. Effects of Modification of Light Parameters on the Production of Cryptophycin, Cyanotoxin with Potent Anticancer Activity, in Nostoc sp. Toxins (Basel) 2020; 12:toxins12120809. [PMID: 33371249 PMCID: PMC7766261 DOI: 10.3390/toxins12120809] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/15/2020] [Accepted: 12/16/2020] [Indexed: 02/03/2023] Open
Abstract
Cryptophycin-1 is a cyanotoxin produced by filamentous cyanobacteria. It has been evaluated as an anticancer agent with great potential. However, its synthesis provides insufficient yield for industrial use. An alternative solution for metabolite efficient production is to stress cyanobacteria by modifying the environmental conditions of the culture (Nostoc sp. ATCC 53789). Here, we examined the effects of light photoperiod, wavelength, and intensity. In light photoperiod, photoperiods 24:0 and 16:8 (light:dark) were tested while in wavelength, orange-red light was compared with blue. Medium, high, and very high light intensity experiments were performed to test the effect of light stress. For a 10-day period, growth was measured, metabolite concentration was calculated through HPLC, and the related curves were drawn. The differentiation of light wavelength had a major effect on the culture, as orange-red filter contributed to noticeable increase in both growth and doubled the cyanotoxin concentration in comparison to blue light. Remarkably, constant light provides higher cryptophycin yield, but slightly lower growth rate. Lastly, the microorganism prefers medium light intensities for both growth and metabolite expression. The combination of these optimal conditions would contribute to the further exploitation of cryptophycin.
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Affiliation(s)
- Alexandros Polyzois
- Produits Naturels, Analyse et Synthèse, Université de Paris, UMR CNRS 8038 CITCOM, Faculté de Pharmacie de Paris, 75006 Paris, France;
- Correspondence: (A.P.); (S.M.); Tel.: +33-153739803 (S.M.)
| | - Diana Kirilovsky
- Institute for Integrative Biology of the Cell (12BC), CEA, CNRS, Université Paris-Sud, Université Paris-Saclay, 91198 Gif-sur-Yvette, France;
| | - Thi-hanh Dufat
- Produits Naturels, Analyse et Synthèse, Université de Paris, UMR CNRS 8038 CITCOM, Faculté de Pharmacie de Paris, 75006 Paris, France;
| | - Sylvie Michel
- Produits Naturels, Analyse et Synthèse, Université de Paris, UMR CNRS 8038 CITCOM, Faculté de Pharmacie de Paris, 75006 Paris, France;
- Correspondence: (A.P.); (S.M.); Tel.: +33-153739803 (S.M.)
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Chintalapati P, Mohseni M. Degradation of cyanotoxin microcystin-LR in synthetic and natural waters by chemical-free UV/VUV radiation. J Hazard Mater 2020; 381:120921. [PMID: 31374374 DOI: 10.1016/j.jhazmat.2019.120921] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
This study investigated the capability of ultraviolet radiation at 254 nm and 185 nm (UV/VUV) to degrade cyanotoxin microcystin-LR (MC-LR). Results showed 70% toxin reduction solely by 254 nm direct photolysis (ε254 = 13,225 ± 814 M-1cm-1; Φ254 = 0.29 ± 0.03 mol/Einstein). The addition of 185 nm increased MC-LR degradation through advanced oxidation by •OH (k•OH,MC-LR = 2.25 ± 0.39 × 1010 M-1s-1). Alkalinity and organics (DOC) reduced MC-LR degradation by scavenging •OH (kobs,MilliQ = 0.117 cm2/mJ; kobs,50ppmAlk. = 0.0497 cm2/mJ; kobs,6ppmDOC = 0.019 cm2/mJ). Chloride absorbed 185 nm, impacting •OH formation and generating Cl•, while also scavenging •OH. However, Cl• is reactive and •OH scavenging is reversible, resulting in relatively low impact on MC-LR degradation (kobs,50ppmCl = 0.0939 cm2/mJ). In natural water, MC-LR could be degraded from a typical concentration (˜15 μg/L) to below detection (<0.5 μg/L) with a UV254 fluence of 200 mJ/cm2 using UV/VUV. The presence of cyanobacterial cells impeded MC-LR degradation; however, 90% MC-LR degradation could still be achieved. UV/VUV is a promising chemical-free technology capable of MC-LR degradation in a variety of water conditions, and a potentially suitable treatment option for small, remote communities.
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Affiliation(s)
- Pranav Chintalapati
- Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada.
| | - Madjid Mohseni
- Department of Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC V6T 1Z3, Canada.
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Tao Y, Hou D, Zhou T, Cao H, Zhang W, Wang X. UV-C suppression on hazardous metabolites in Microcystis aeruginosa: Unsynchronized production of microcystins and odorous compounds at population and single-cell level. J Hazard Mater 2018; 359:281-289. [PMID: 30041121 DOI: 10.1016/j.jhazmat.2018.07.052] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Revised: 06/28/2018] [Accepted: 07/11/2018] [Indexed: 06/08/2023]
Abstract
The effectiveness of UV-C towards the toxin and odor of M. aeruginosa at population and single cell levels were investigated in three ways. In the absence of UV-C, MC-LR and β-cyclocitral production show similar pattern of incremental rate with growth rate on population level shown as intracellular concentrations of MC-LR (CMC) and β-cyclocitral (CBCC), but the cellular quota of MC-LR (QMC) and β-cyclocitral (QBCC) at single-cell level reached the maximum values, 37.5 ± 1.2 fg cell-1 and 4.3 ± 0.1 fg cell-1, just after the early exponential phase. Second, upon UV-C irradiation, the CMC consistently decreased by 10-41% with increase of UV-C dosage (50-200 mJ cm-2) while CBCC increased by 2-14%. Third, during the 14 days' post-UV incubation, UV-C at 75-200 mJ cm-2 induced remarkable suppressing effects on both CMC and CBCC for 3-14 days. The suppressing effects on QMC and QBCC were induced by UV-C at 100 mJ cm-2 and above, with shorter suppressing periods by 1-4 days and lower decremental rates by 21%-30% than that of CMC and CBCC, indicating interruptions on biosynthesis processes partially contribute to suppression effects of CMC and CBCC. The suppression effect on either CBCC or QBCC, with higher decrement rates while lower recovery rates, was more severe than CMC and QMC.
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Affiliation(s)
- Yi Tao
- Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China; Shenzhen Environmental Science and New Energy Technology Engineering Laboratory, Tsinghua-Berkeley Shenzhen Institute, Shenzhen, 518055, China.
| | - Delin Hou
- Guangdong Provincial Engineering Research Center for Urban Water Recycling and Environmental Safety, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China
| | - Tingru Zhou
- Key Laboratory of Microorganism Application and Risk Control (MARC) of Shenzhen, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China
| | - Huansheng Cao
- Biodesign Center for Fundamental and Applied Microbiomics, Arizona State University, Tempe, AZ, 85287, USA
| | - Wen Zhang
- Department of Civil and Environmental Engineering, New Jersey Institute of Technology, Newark, New Jersey, USA
| | - Xuejian Wang
- Key Laboratory of Microorganism Application and Risk Control (MARC) of Shenzhen, Graduate School at Shenzhen, Tsinghua University, Shenzhen, 518055, China
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Sun Q, Zhang T, Wang F, Liu C, Wu C, Xie RR, Zheng Y. Ultraviolet photosensitized transformation mechanism of microcystin-LR by natural organic matter in raw water. Chemosphere 2018; 209:96-103. [PMID: 29913404 DOI: 10.1016/j.chemosphere.2018.06.091] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Revised: 06/04/2018] [Accepted: 06/12/2018] [Indexed: 06/08/2023]
Abstract
Microcystins (MCs), produced by cyanobacterial blooms in eutrophic water, are common toxic metabolites and a potential threat to human health. However, the mechanism of MC photodegradation by photosensitizers in raw water remains unclear. In photodegradation and quenching experiments, this study investigates the photosensitized degradation of microcystin-LR (MC-LR) by fulvic acid (FA, a kind of dissolved organic matter with natural photosensitizing properties) under ultraviolet (UV) light irradiation. The photodegradation mechanisms of FA are also explored. The photodegradation process of MC-LR by FA was consistent with second-order reaction kinetics. The degradation rate of MC-LR in FA decreased from 80% to 55% as the pH increased from 3 to 9, because the binding ability of FA to MC-LR reduces as the pH increases. Given that FA can both inhibit and promote MC-LR degradation depending on its concentration, the optimum initial FA concentration for degrading MC-LR was determined as 9.86 mgC·L-1. The excited triplet state of FA (3FA∗) accounted for 50.12% of the MC-LR loss; the remaining loss (49.88%) was contributed by reactive oxygen species and direct photolysis. This implies that the main pathway of MC-LR degradation is reaction with 3FA∗. The MC-LR degradation rate is 36% higher under UV irradiation than that under simulated sunlight irradiation.
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Affiliation(s)
- Qiyuan Sun
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; Key Laboratory of Resource Cycle and Pollution Control of Fujian Province, Fujian Normal University, Fuzhou 350007, China
| | - Tianfang Zhang
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China
| | - Feifeng Wang
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; Key Laboratory of Resource Cycle and Pollution Control of Fujian Province, Fujian Normal University, Fuzhou 350007, China.
| | - Changqing Liu
- Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; College of Geographical Sciences, Fujian Normal University, Fuzhou 350007, China
| | - Chunshan Wu
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; Key Laboratory of Resource Cycle and Pollution Control of Fujian Province, Fujian Normal University, Fuzhou 350007, China
| | - Rong-Rong Xie
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; Key Laboratory of Resource Cycle and Pollution Control of Fujian Province, Fujian Normal University, Fuzhou 350007, China
| | - Yuyi Zheng
- College of Environmental Science and Engineering, Fujian Normal University, Fuzhou 350007, China; Institute of Environmental Science, Fujian Normal University, Fuzhou 350007, China; Key Laboratory of Resource Cycle and Pollution Control of Fujian Province, Fujian Normal University, Fuzhou 350007, China.
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Liu Y, Ren J, Wang X, Fan Z. Mechanism and Reaction Pathways for Microcystin-LR Degradation through UV/H2O2 Treatment. PLoS One 2016; 11:e0156236. [PMID: 27281173 PMCID: PMC4900665 DOI: 10.1371/journal.pone.0156236] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/11/2016] [Indexed: 11/18/2022] Open
Abstract
Microcystin-LR (MCLR) is the most common cyanotoxin in contaminated aquatic systems. MCLR inhibits protein phosphatases 1 and 2A, leading to liver damage and tumor formation. MCLR is relatively stable owing to its cyclic structures. The combined UV/H2O2 technology can degrade MCLR efficiently. The second-order rate constant of the reaction between MCLR and hydroxyl radical (·OH) is 2.79(±0.23)×1010 M−1 s−1 based on the competition kinetics model using nitrobenzene as reference compound. The probable degradation pathway was analyzed through liquid chromatography mass spectrometry. Results suggested that the major destruction pathways of MCLR were initiated by ·OH attack on the benzene ring and diene of the Adda side chain. The corresponding aldehyde or ketone peptide residues were formed through further oxidation. Another minor destruction pathway involved ·OH attack on the methoxy group of the Adda side chain, followed by complete removal of the methoxy group. The combined UV/H2O2 system is a promising technology for MCLR removal in contaminated aquatic systems.
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Affiliation(s)
- Yafeng Liu
- Department of environmental science & engineering, Fudan University, Shanghai, 200433, China
| | - Jing Ren
- Department of environmental science & engineering, Fudan University, Shanghai, 200433, China
| | - Xiangrong Wang
- Department of environmental science & engineering, Fudan University, Shanghai, 200433, China
| | - Zhengqiu Fan
- Department of environmental science & engineering, Fudan University, Shanghai, 200433, China
- * E-mail:
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He X, de la Cruz AA, Hiskia A, Kaloudis T, O'Shea K, Dionysiou DD. Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms. Water Res 2015; 74:227-238. [PMID: 25744186 DOI: 10.1016/j.watres.2015.02.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 02/04/2015] [Accepted: 02/06/2015] [Indexed: 06/04/2023]
Abstract
Hepatotoxic microcystins (MCs) are the most frequently detected group of cyanobacterial toxins. This study investigated the degradation of common MC variants in water, MC-LR, MC-RR, MC-YR and MC-LA, by UV-254 nm-based processes, UV only, UV/H2O2, UV/S2O8(2-) and UV/HSO5(-). Limited direct photolysis of MCs was observed, while the addition of an oxidant significantly improved the degradation efficiency with an order of UV/S2O8(2-) > UV/HSO5(-) > UV/H2O2 at the same initial molar concentration of the oxidant. The removal of MC-LR by UV/H2O2 appeared to be faster than another cyanotoxin, cylindrospermopsin, at either the same initial molar concentration or the same initial organic carbon concentration of the toxin. It suggested a faster reaction of MC-LR with hydroxyl radical, which was further supported by the determined second-order rate constant of MCs with hydroxyl radical. Both isomerization and photohydration byproducts were observed in UV only process for all four MCs; while in UV/H2O2, hydroxylation and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in the structure of MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061; while the presence of a second arginine in MC-RR led to the elimination of a guanidine group and the absence of double bond cleavage byproducts. It was therefore demonstrated in this study that the variable amino acids in the structure of MCs influenced not only the degradation kinetics but also the preferable reaction mechanisms.
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Affiliation(s)
- Xuexiang He
- Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Nireas-International Water Research Centre, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
| | - Armah A de la Cruz
- Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH 45268, United States
| | - Anastasia Hiskia
- Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, National Center for Scientific Research "Demokritos", Patriarchou Grigoriou & Neapoleos, 15310 Agia Paraskevi, Athens, Greece
| | - Triantafyllos Kaloudis
- Water Quality Department, Athens Water Supply and Sewerage Company (EYDAP SA), Oropou 156, 11146 Galatsi, Athens, Greece
| | - Kevin O'Shea
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, United States
| | - Dionysios D Dionysiou
- Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Nireas-International Water Research Centre, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.
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El-Sheikh SM, Zhang G, El-Hosainy HM, Ismail AA, O'Shea KE, Falaras P, Kontos AG, Dionysiou DD. High performance sulfur, nitrogen and carbon doped mesoporous anatase-brookite TiO₂ photocatalyst for the removal of microcystin-LR under visible light irradiation. J Hazard Mater 2014; 280:723-733. [PMID: 25238189 DOI: 10.1016/j.jhazmat.2014.08.038] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 06/03/2023]
Abstract
Carbon, nitrogen and sulfur (C, N and S) doped mesoporous anatase-brookite nano-heterojunction titania photocatalysts have been synthesized through a simple sol-gel method in the presence of triblock copolymer Pluronic P123. XRD and Raman spectra revealed the formation of anatase and brookite mixed phases. XPS spectra indicated the presence of C, N and S dopants. The TEM images demonstrated the formation of almost monodisperse titania nanoparticles with particle sizes of approximately 10nm. N2 isotherm measurements confirmed that both doped and undoped titania anatase-brookite materials have mesoporous structure. The photocatalytic degradation of the cyanotoxin microcystin-LR (MC-LR) has been investigated using these novel nanomaterials under visible light illumination. The photocatalytic efficiency of the mesoporous titania anatase-brookite photocatalyst dramatically increased with the addition of the C, N and S non-metal, achieving complete degradation (∼ 100 %) of MC-LR. The results demonstrate the advantages of the synthetic approach and the great potential of the visible light activated C, N, and S doped titania photocatalysts for the treatment of organic micropollutants in contaminated waters under visible light.
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Affiliation(s)
- Said M El-Sheikh
- Nanostructured Materials Lab., Advanced Materials Department, CMRDI, Cairo 11421, Egypt
| | - Geshan Zhang
- Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, United States
| | - Hamza M El-Hosainy
- Nanostructured Materials Lab., Advanced Materials Department, CMRDI, Cairo 11421, Egypt
| | - Adel A Ismail
- Nanostructured Materials Lab., Advanced Materials Department, CMRDI, Cairo 11421, Egypt
| | - Kevin E O'Shea
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, United States
| | - Polycarpos Falaras
- Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems (IAMPPNM), National Centre for Scientific Research "Demokritos", Agia Paraskevi Attikis, 15310 Athens, Greece
| | - Athanassios G Kontos
- Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems (IAMPPNM), National Centre for Scientific Research "Demokritos", Agia Paraskevi Attikis, 15310 Athens, Greece
| | - Dionysios D Dionysiou
- Environmental Engineering and Science Program, Department of Biomedical, Chemical and Environmental Engineering, University of Cincinnati, Cincinnati, OH 45221, United States.
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He X, Zhang G, de la Cruz AA, O'Shea KE, Dionysiou DD. Degradation mechanism of cyanobacterial toxin cylindrospermopsin by hydroxyl radicals in homogeneous UV/H₂O₂ process. Environ Sci Technol 2014; 48:4495-4504. [PMID: 24625255 DOI: 10.1021/es403732s] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The degradation of cylindrospermopsin (CYN), a widely distributed and highly toxic cyanobacterial toxin (cyanotoxin), remains poorly elucidated. In this study, the mechanism of CYN destruction by UV-254 nm/H2O2 advanced oxidation process (AOP) was investigated by mass spectrometry. Various byproducts identified indicated three common reaction pathways: hydroxyl addition (+16 Da), alcoholic oxidation or dehydrogenation (-2 Da), and elimination of sulfate (-80 Da). The initiation of the degradation was observed at the hydroxymethyl uracil and tricyclic guanidine groups; uracil moiety cleavage/fragmentation and further ring-opening of the alkaloid were also noted at an extended reaction time or higher UV fluence. The degradation rates of CYN decreased and less byproducts (species) were detected using natural water matrices; however, CYN was effectively eliminated under extended UV irradiation. This study demonstrates the efficiency of CYN degradation and provides a better understanding of the mechanism of CYN degradation by hydroxyl radical, a reactive oxygen species that can be generated by most AOPs and is present in natural water environment.
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Affiliation(s)
- Xuexiang He
- Environmental Engineering and Science Program, University of Cincinnati , Cincinnati, Ohio 45221-0012, United States
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Zong W, Sun F, Sun X. Oxidation by-products formation of microcystin-LR exposed to UV/H2O2: toward the generative mechanism and biological toxicity. Water Res 2013; 47:3211-3219. [PMID: 23562502 DOI: 10.1016/j.watres.2013.03.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/11/2013] [Accepted: 03/16/2013] [Indexed: 06/02/2023]
Abstract
The presence of microcystins (MCs) in water sources is of concern due to their direct threats to human health and potential to form oxidation by-products (OBPs) in finished water. To control the environmental risk of MCs related OBPs, we evaluated their generative mechanisms and biological toxicity by mass spectrometry technology and molecular toxicity experiment. Exposed to UV/H2O2, model toxin microcystin-LR (MCLR) in clean water was quickly transformed but successively generated seven types of MCLR-OBPs with the chemical formulas of C49H74N10O13, C49H76N10O14, C49H78N10O16, C49H76N10O15, C37H58N10O12, C33H54N10O12, and C34H54N10O12. Probable isomers for each MCLR-OBP type were then separated and identified, indicating the aromatic ring and conjugated diene in Adda and the CC bond in Mdha were the major target sites of oxidation. Though subsequent toxicology data showed the toxicity of MCLR-OBPs on protein phosphatases 1 and 2A decreased with the extending of treatment by and large, they still possessed considerable biological toxicity (especially for product d). Influenced by MCLR-OBP distribution, concentration and residual toxicity, the secondary pollution of MCLR-OBPs in drinking water also deserved further attention even though MCLR was totally destroyed.
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Affiliation(s)
- Wansong Zong
- College of Population, Resources and Environment, Shandong Normal University, 88 East Wenhua Road, Jinan, Shandong 250014, PR China.
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Song W, Yan S, Cooper WJ, Dionysiou DD, O'Shea KE. Hydroxyl radical oxidation of cylindrospermopsin (cyanobacterial toxin) and its role in the photochemical transformation. Environ Sci Technol 2012; 46:12608-12615. [PMID: 23082747 DOI: 10.1021/es302458h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Cylindrospermopsin (CYN), an alkaloid guanidinium sulfated toxin, is produced by a number of cyanobacteria regularly found in lakes, rivers, and reservoirs. Steady-state and time-resolved radiolysis methods were used to determine reaction pathways and kinetic parameters for the reactions of hydroxyl radical with CYN. The absolute bimolecular reaction rate constant for the reaction of hydroxyl radical with CYN is (5.08 ± 0.16) × 10(9) M(-1) s(-1). Comparison of the overall reaction rate of CYN with hydroxyl radical with the individual reaction rate for addition to the uracil ring in CYN indicate the majority of the hydroxyl radicals (84%) react at the uracil functionality of CYN. Product analyses using liquid chromatography-mass spectrometry indicate the major products from the reaction of hydroxyl radical with CYN involve attack of hydroxyl radical at the uracil ring and hydrogen abstraction from the hydroxy-methine bridge linking the uracil ring to the tricyclic guanidine functionality. The role of hydroxyl radical initiated pathways in the natural organic matter (NOM) photosensitized transformation of CYN were evaluated. Scavenger and trapping experiments indicate that hydroxyl radical mediated transformations account for approximately ~70% of CYN destruction in surface waters under solar irradiation in the presence of NOM. The absence of solvent isotope effect indicates singlet oxygen does not play a significant role in the NOM sensitized transformation of CYN. The primary degradation pathways for HO• mediated and NOM photosensitized destruction of CYN involve destruction of the uracil ring. The fundamental kinetic parameters determined from these studies are critical for the accurate evaluation of hydroxyl-radical based technologies for the remediation of this problematic cyanotoxin in drinking water and important in the assessment of the environmental oxidative transformation of uracil based compounds.
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Affiliation(s)
- Weihua Song
- Department of Environmental Science and Engineering, Fudan University, Shanghai, 200433, PR China.
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Ma Q, Ren J, Huang H, Wang S, Wang X, Fan Z. Kinetic and mechanistic study of microcystin-LR degradation by nitrous acid under ultraviolet irradiation. J Hazard Mater 2012; 215-216:75-82. [PMID: 22410721 DOI: 10.1016/j.jhazmat.2012.02.033] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Revised: 02/05/2012] [Accepted: 02/13/2012] [Indexed: 05/31/2023]
Abstract
Degradation of microcystin-LR (MC-LR) in the presence of nitrous acid (HNO(2)) under irradiation of 365nm ultraviolet (UV) was studied for the first time. The influence of initial conditions including pH value, NaNO(2) concentration, MC-LR concentration and UV intensity were studied. MC-LR was degraded in the presence of HNO(2); enhanced degradation of MC-LR was observed with 365nm UV irradiation, caused by the generation of hydroxyl radicals through the photolysis of HNO(2). The degradation processes of MC-LR could well fit the pseudo-first-order kinetics. Mass spectrometry was applied for identification of the byproducts and the analysis of degradation mechanisms. Major degradation pathways were proposed according to the results of LC-MS analysis. The degradation of MC-LR was initiated via three major pathways: attack of hydroxyl radicals on the conjugated carbon double bonds of Adda, attack of hydroxyl radicals on the benzene ring of Adda, and attack of nitrosonium ion on the benzene ring of Adda.
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Affiliation(s)
- Qingwei Ma
- Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, China
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Triantis TM, Fotiou T, Kaloudis T, Kontos AG, Falaras P, Dionysiou DD, Pelaez M, Hiskia A. Photocatalytic degradation and mineralization of microcystin-LR under UV-A, solar and visible light using nanostructured nitrogen doped TiO2. J Hazard Mater 2012; 211-212:196-202. [PMID: 22169146 DOI: 10.1016/j.jhazmat.2011.11.042] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Revised: 11/09/2011] [Accepted: 11/12/2011] [Indexed: 05/31/2023]
Abstract
In an attempt to face serious environmental hazards, the degradation of microcystin-LR (MC-LR), one of the most common and more toxic water soluble cyanotoxin compounds released by cyanobacteria blooms, was investigated using nitrogen doped TiO(2) (N-TiO(2)) photocatalyst, under UV-A, solar and visible light. Commercial Degussa P25 TiO(2), Kronos and reference TiO(2) nanopowders were used for comparison. It was found that under UV-A irradiation, all photocatalysts were effective in toxin elimination. The higher MC-LR degradation (99%) was observed with Degussa P25 TiO(2) followed by N-TiO(2) with 96% toxin destruction after 20 min of illumination. Under solar light illumination, N-TiO(2) nanocatalyst exhibits similar photocatalytic activity with that of commercially available materials such as Degussa P25 and Kronos TiO(2) for the destruction of MC-LR. Upon irradiation with visible light Degussa P25 practically did not show any response, while the N-TiO(2) displayed remarkable photocatalytic efficiency. In addition, it has been shown that photodegradation products did not present any significant protein phosphatase inhibition activity, proving that toxicity is proportional only to the remaining MC-LR in solution. Finally, total organic carbon (TOC) and inorganic ions (NO(2)(-), NO(3)(-) and NH(4)(+)) determinations confirmed that complete photocatalytic mineralization of MC-LR was achieved under both UV-A and solar light.
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Affiliation(s)
- T M Triantis
- Laboratory of Catalytic - Photocatalytic Processes (Solar Energy - Environment), Institute of Physical Chemistry, National Center for Scientific Research Demokritos, Neapoleos 25, 15310 Agia Paraskevi, Attiki, Greece
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He X, Pelaez M, Westrick JA, O'Shea KE, Hiskia A, Triantis T, Kaloudis T, Stefan MI, de la Cruz AA, Dionysiou DD. Efficient removal of microcystin-LR by UV-C/H₂O₂ in synthetic and natural water samples. Water Res 2012; 46:1501-1510. [PMID: 22177771 DOI: 10.1016/j.watres.2011.11.009] [Citation(s) in RCA: 121] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 10/01/2011] [Accepted: 11/04/2011] [Indexed: 05/31/2023]
Abstract
The destruction of the commonly found cyanobacterial toxin, microcystin-LR (MC-LR), in surface waters by UV-C/H(2)O(2) advanced oxidation process (AOP) was studied. Experiments were carried out in a bench scale photochemical apparatus with low pressure mercury vapor germicidal lamps emitting at 253.7 nm. The degradation of MC-LR was a function of UV fluence. A 93.9% removal with an initial MC-LR concentration of 1 μM was achieved with a UV fluence of 80 mJ/cm(2) and an initial H(2)O(2) concentration of 882 μM. When increasing the concentration of MC-LR only, the UV fluence-based pseudo-first order reaction rate constant generally decreased, which was probably due to the competition between by-products and MC-LR for hydroxyl radicals. An increase in H(2)O(2) concentration led to higher removal efficiency; however, the effect of HO scavenging by H(2)O(2) became significant for high H(2)O(2) concentrations. The impact of water quality parameters, such as pH, alkalinity and the presence of natural organic matter (NOM), was also studied. Field water samples from Lake Erie, Michigan and St. Johns River, Florida were employed to evaluate the potential application of this process for the degradation of MC-LR. Results showed that the presence of both alkalinity (as 89.6-117.8 mg CaCO(3)/L) and NOM (as ∼2 to ∼9.5 mg/L TOC) contributed to a significant decrease in the destruction rate of MC-LR. However, a final concentration of MC-LR bellow the guideline value of 1 μg/L was still achievable under current experimental conditions when an initial MC-LR concentration of 2.5 μg/L was spiked into those real water samples.
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Affiliation(s)
- Xuexiang He
- Environmental Engineering and Science Program, University of Cincinnati, 705 Engineering Research Center, Cincinnati, OH 45221-0012, USA
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Chen P, Zhu L, Fang S, Wang C, Shan G. Photocatalytic degradation efficiency and mechanism of microcystin-RR by mesoporous Bi₂WO₆ under near ultraviolet light. Environ Sci Technol 2012; 46:2345-2351. [PMID: 22250846 DOI: 10.1021/es2036338] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Microcystin-RR (MC-RR) is one of the most common cyanotoxin microcystins in fresh water and is of great concern due to its potential hepatotoxicity. In the present study, Bi(2)WO(6) was synthesized with a hydrothermal method by varying the pH of the reaction solution in the range of 1-11. The surface area of the catalysts decreased, but the crystallinity and crystal size increased with the pH. The adsorption and degradation capacities of the catalysts decreased with increasing the preparation solution pH. The Bi(2)WO(6) prepared at pH 1 (Bi(2)WO(6)-pH1) displayed the highest adsorption and degradation capacity to MC-RR even though it consisted of randomly aggregated particles. Nearly 100% of MC-RR at 10 mg L(-1) was removed after 30 min of irradiation of near-ultraviolet light (300-400 nm) in a solution with Bi(2)WO(6) concentration of 0.2 g L(-1). The photodegradation efficiency of Bi(2)WO(6)-pH1 was greater in acid medium than in basic solutions. Several intermediate products were observed and identified by liquid chromatography/mass spectrometry/mass spectrometry, and a unique photodegradation pathway was proposed. It was assumed that a photo-Kolbe process happened at the site carboxyl acid group of the d-Glu residue by the photogenerated holes, producing a hydroperoxyl product at m/z 513.8. This intermediate could be further decomposed to an alcohol product at m/z 505.8 and a ketone product at m/z 504.8. The aromatic ring and diene bond of the Adda chain could also be attacked by the holes and form phenol and diol products.
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Affiliation(s)
- Peng Chen
- College of Environmental Science and Engineering, Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Key Laboratory of Environmental Remediation and Pollution Control, Nankai University, Tianjin 300071, People's Republic of China
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Pelaez M, de la Cruz AA, O'Shea K, Falaras P, Dionysiou DD. Effects of water parameters on the degradation of microcystin-LR under visible light-activated TiO2 photocatalyst. Water Res 2011; 45:3787-3796. [PMID: 21575981 DOI: 10.1016/j.watres.2011.04.036] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2011] [Revised: 04/16/2011] [Accepted: 04/18/2011] [Indexed: 05/30/2023]
Abstract
A study was performed to determine the effect of pH, alkalinity, natural organic matter (NOM) and dissolved oxygen in the performance of nitrogen and fluorine doped TiO(2) (NF-TiO(2)) for the degradation of hepatotoxin microcystin-LR (MC-LR) in synthetic and natural water under visible light irradiation. The initial degradation rate of MC-LR was fastest under acidic conditions (3.50 ± 0.02 × 10(-3) μM min(-1) at pH 3.0) and decreased to 2.29 ± 0.07 × 10(-3) and 0.54 ± 0.02 × 10(-3) μM min(-1) at pH 5.7 and 7.1, respectively. Attractive forces between the opposite charged MC-LR and NF-TiO(2) are likely responsible for the enhancement in the photocatalytic decomposition of MC-LR resulting from increased interfacial adsorption. For carbonate buffered solutions, the photocatalytic activity of NF-TiO(2) was reduced when increasing the carbonate concentration up to 150 mg CaCO(3) L(-1). The scavenging of radical species by the bicarbonate ion at pH 7.1 is discussed. In the presence of NOM, the degradation rates decreased as pH and initial concentration of the NOM increased. The inhibition was higher with fulvic acid than humic acid under alkaline conditions. Oxygenated solution yields higher NF-TiO(2) photocatalytic degradation of MC-LR compared to nitrogen sparged solution at pH 5.7. The involvement of specific reactive oxygen species implicated in the photodegradation is proposed. Finally, no significant degradation is observed with various natural waters spiked with MC-LR under visible light (λ > 420 nm) but high removal was achieved with simulated solar light. This study provides a better understanding of the interactions and photocatalytic processes initiated by NF-TiO(2) under visible and solar light. The results indicate solar photocatalytic oxidation is a promising technology for the treatment of water contaminated with cyanotoxins.
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Affiliation(s)
- Miguel Pelaez
- Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0071, USA
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Abstract
Microcystins (MCs) produced by cyanobacteria are strong hepatotoxins and classified as possible carcinogens. MCs pose a considerable threat to human health through tainted drinking and surface waters. Herein filtrated water from a waterworks in Harbin, China, was spiked with microcystin-LR (MC-LR) extracted from a toxic scum of microcystis aeruginosa, and the spiked sample waters were treated using UV irradiation with consequent ozonation process (UV/O3), compared with ozonation at a dose range commonly applied in water treatment plants, UV irradiation at 254 nm and UV irradiation combined with ozonation (UV+O3), respectively. The remaining of toxins were analyzed using high-performance liquid chromatography and also determined using a protein phosphatase type 2A inhibition assay, which was utilized to evaluate the reduction in toxicity. Results indicated that in comparison to other three processes (O3, UV, and UV+O3), UV/O3 process could effectively decrease both the concentration and toxicity of MC-LR at 100 microg/L level after 5 min UV irradiation with consequent 5 min ozonation at 0.2 mg/L (below 1 microg/L), while 0.5 mg/L ozone dose was required for the level below 0.1 microg/L. The addition of an UV treatment step to the existing treatment train may induce significant transformation of micropollutants and breaks down the natural organic matters into moieties unfavorable for ozone decomposition, stabilizing the ozone residual. These findings suggested that sequential use of UV and ozone may be a suitable method for the removal of these potentially hazardous microcystins from drinking water.
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Affiliation(s)
- Xiaowei Liu
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China.
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Guo JW, Gao NY, Yin DD, Li L, Dong BZ, Zhang KJ. [Degradation of MC-LR by combination of UV/H2O2 process]. Huan Jing Ke Xue 2009; 30:457-462. [PMID: 19402498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The degradation of MC-LR in water by UV/H2O2 process was investigated. The effects of intensity of UV radiation, initial concentration of MC-LR, dosages of H2O2, initial pH value and anions on degradation of MC-LR by UV/H2O2 process were studied. The results show that the removal of MC-LR only by H2O2 is nearly zero, and UV process can degrade MC-LR to a certain extent. However, the degradation efficiency of UV/H2O2 process is much higher than UV and H2O2 process due to the synergetic effect between UV and H2O2. The removal of MC-LR increases with the enhancement of intensity of UV radiation, but decreases gradually with the increase of initial concentration of MC-LR. When the dosages of H2O2 change from 1 mmol/L to 3 mmol/L, the constant of degradation rate rises from 0.0844 to 0.1664. The optimum pH value is 3.13. The added anions have adverse effect on the degradation of MC-LR, especially carbonate and nitrate ions have the biggest influence among the studied anions.
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Affiliation(s)
- Jian-Wei Guo
- State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China.
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Choi H, Antoniou MG, Pelaez M, De la Cruz AA, Shoemaker JA, Dionysiou DD. Mesoporous nitrogen-doped TiO2 for the photocatalytic destruction of the cyanobacterial toxin microcystin-LR under visible light irradiation. Environ Sci Technol 2007; 41:7530-7535. [PMID: 18044537 DOI: 10.1021/es0709122] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The presence of the harmful cyanobacterial toxins in water resources worldwide drives the development of an innovative and practical water treatment technology with great urgency. This study deals with two important aspects: the fabrication of mesoporous nitrogen-doped TiO2 (N-TiO2) photocatalysts and their environmental application for the destruction of microcystin-LR (MC-LR) under visible light. In a nanotechnological sol-gel synthesis method, a nitrogen-containing surfactant (dodecylammonium chloride) was introduced as a pore templating material for tailor-designing the structural properties of TiO2 and as a nitrogen dopant for its visible light response. The resulting N-TiO2 exhibited significantly enhanced structural properties including 2-8 nm mesoporous structure (porosity 44%) and high surface area of 150 m2/g. Red shift in light absorbance up to 468 nm, 0.9 eV lower binding energy of electrons in Ti 2p state, and reduced interplanar distance of crystal lattices proved nitrogen doping in the TiO2 lattice. Due to its narrow band gap at 2.65 eV, N-TiO2 efficiently degraded MC-LR under visible spectrum above 420 nm. Acidic condition (pH 3.5) was more favorable for the adsorption and photocatalytic degradation of MC-LR on N-TiO2 due to electrostatic attraction forces between negatively charged MC-LR and +6.5 mV charged N-TiO2. Even under UV light, MC-LR was decomposed 3-4 times faster using N-TiO2 than control TiO2. The degradation pathways and reaction intermediates of MC-LR were not directly related to the energy source for TiO2 activation (UV and visible) and nature of TiO2 (neat and nitrogen-doped). This study implies a strong possibility for the in situ photocatalytic remediation of contaminated water with cyanobacterial toxins and other toxic compounds using solar light, a sustainable source of energy.
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Affiliation(s)
- Hyeok Choi
- Department of Civil and Environmental Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0071, USA
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Hudder A, Song W, O'Shea KE, Walsh PJ. Toxicogenomic evaluation of microcystin-LR treated with ultrasonic irradiation. Toxicol Appl Pharmacol 2007; 220:357-64. [PMID: 17383702 PMCID: PMC1971717 DOI: 10.1016/j.taap.2007.02.004] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2006] [Revised: 02/08/2007] [Accepted: 02/11/2007] [Indexed: 11/29/2022]
Abstract
Microcystins are a family of toxins produced by cyanobacteria found throughout the world in marine and freshwater environments. The most commonly encountered form of microcystin is microcystin-LR (MC-LR). Humans are exposed to MC-LR by drinking contaminated water. The toxin accumulates rapidly in the liver where it exerts most of its damage. Treatment of water containing MC-LR by ultrasonic irradiation leads to the breakdown of the toxin. Both the parent toxin and the treated toxin reaction products (TTRP) were evaluated for toxic effects in mice. Animals were exposed to purified MC-LR or an equivalent dose of the TTRP and sacrificed after 4 h or 24 h. Serum was collected and assayed for lactate dehydrogenase (LDH) activity as an indicator of hepatotoxicity. LDH activity was detected in the serum of MC-LR exposed mice indicative of liver damage, but not in control mice. Only a fraction of that activity was detectable in mice exposed to TTRP. Liver RNA was used for microarray analysis and real-time PCR. Individual animals varied in their overall genomic response to the toxin; however, only 20 genes showed consistent changes in expression. These include chaperones which may be part of a generalized stress response; cytochrome P450 which may be involved in metabolizing the toxin; and lipid dystrophy genes such as lipin-2, uridine phosphorylase and a homolog to tribbles, a stress-inducible gene involved in cell death. Of the genes that responded to the MC-LR, none showed significant changes in expression profile in response to TTRP. Taken together, the data indicate that ultrasonic irradiation of MC-LR effectively reduces hepatotoxicity in mice and therefore may be a useful method for detoxification of drinking water.
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Affiliation(s)
- Alice Hudder
- Division of Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Virginia Key, FL 33149, USA
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SONG WEIHUA, DE LA CRUZ ARMAHA, REIN KATHLEEN, O'SHEA KEVINE. Ultrasonically induced degradation of microcystin-LR and -RR: identification of products, effect of pH, formation and destruction of peroxides. Environ Sci Technol 2006; 40:3941-6. [PMID: 16830565 PMCID: PMC2573036 DOI: 10.1021/es0521730] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Microcystins (MCs) are a family of toxic peptides produced by a number of cyanobacteria commonly found in lakes, water reservoirs, and recreational facilities. The increased eutrophication of freshwater supplies has led to an increase in the incidence of cyanobacterial harmful algal blooms and concerns over the public health implications of these toxins in the water supply. Conventional water treatment methods are ineffective at removing low concentrations of cyanotoxins, hence specialized treatment is usually recommended for treatment of contaminated water. In this study, the products of ultrasonically induced degradation of microcystin-LR (MC-LR) and microcystin-RR (MC-RR) were analyzed by LC-MS to elucidate the probable pathways of degradation of these toxins. Results indicate preliminary products of sonolysis of MCs are due to the hydroxyl radical attack on the benzene ring and diene of the Adda peptide residue and cleavage of the Mdha-Ala peptide bond. The effect of pH on the toxin degradation was evaluated since the pH of the solution changes upon ultrasonic irradiation and varies with the water quality of treatable waters. The initial rate of MC-LR degradation is greater at acidic pH and coincides with the change in hydrophobic character of MC-LR as a function of pH. Hydrogen and organic peroxides are formed during ultrasonic irradiation, but can be eliminated by adding Fe(II). The addition of Fe(II) also accelerates the degradation of MC-LR, presumably by promoting the formation of hydroxyl radicals via conversion of ultrasonically produced H2O2. These findings suggest that sonolysis can effectively degrade MCs in drinking water.
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Affiliation(s)
| | | | | | - KEVIN E. O'SHEA
- Corresponding author phone: 305−348−3968; fax: 305−348−3772; e-mail:
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