Oxidation of the Cyanobacterial Hepatotoxin Microcystin-LR by Chlorine Dioxide:  Reaction Kinetics, Characterization, and Toxicity of Reaction Products

• Published in: Environmental science & technology Vol. 38; no. 22; pp. 6025 - 6031
• Main Authors: Kull, Tomas P. J, Backlund, Peter H, Karlsson, Krister M, Meriluoto, Jussi A. O
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15.11.2004
• Subjects: Air. Soil. Water. Waste. Feeding; Applied sciences; Bacteria; Biological and medical sciences; Chlorine; Chlorine Compounds - chemistry; Chromatography, High Pressure Liquid; Cyanobacteria; Cyanobacteria - chemistry; Drinking water; Drinking water and swimming-pool water. Desalination; Environment. Living conditions; Enzyme Inhibitors; Eutrophication; Exact sciences and technology; Kinetics; Mass Spectrometry; Medical sciences; Microcystins; Oxidation; Oxidation-Reduction; Oxides - chemistry; Peptides, Cyclic - chemistry; Phosphoric Monoester Hydrolases - antagonists & inhibitors; Pollution; Public health. Hygiene; Public health. Hygiene-occupational medicine; Reaction kinetics; Toxicity; Toxins; Water Microbiology; Water Pollutants, Chemical - analysis; Water treatment; Water treatment and pollution; Chlorination; Cyclic peptides; Phosphoprotein phosphatase; Toxicity; Phosphoric monoester hydrolases; HPLC chromatography; Esterases; Cyanobacteria; Bacteria; Oxidation; Drinking water treatment; Bioassay; Enzyme; Reaction product; Enzyme inhibitor; Disinfection; Chlorine dioxide; Ultraviolet spectrometry; Toxin; Microbial origin; Polypeptide; Bloom; Hydrolases; Kinetics; Mass spectrometry
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es0400032

Cyanobacteria are known producers of cytotoxins, hepatotoxins, and neurotoxins. The main toxins are microcystins, cyclic heptapeptide hepatotoxins, produced by strains of several cyanobacterial genera frequently found in eutrophied freshwaters. Due to the acute and chronic toxicity of microcystins, successful removal of these toxins in drinking water treatment processes is of increasing concern. In the present work the kinetics of microcystin-LR (MC-LR) oxidation by chlorine dioxide (ClO2) was studied with UV-spectrometry and high performance liquid chromatography (HPLC). Characterization of reaction products was performed with mass spectrometric (MS) analysis, while the toxicity of reaction products was tested with a protein phosphatase inhibition assay (PPIA). The main reaction products formed, dihydroxy isomers of MC-LR as identified by MS, were nontoxic according to the PPIA. The overall rate constant k for the reaction between MC-LR and ClO2 at 293 K and pH 5.65 was modest, k = 1.24 M-1 s-1, suggesting that ClO2 is not a suitable oxidant for the degradation of microcystins in drinking water treatment processes.