title: Anaerobic biotransformation of roxarsone and related N-substituted phenylarsonic acids.
abstract: Large quantities of arsenic are introduced into the environment through land application of poultry litter containing the organoarsenical feed additive roxarsone (3-nitro-4-hydroxyphenylarsonic acid). The objective of this study was to evaluate the bioconversion of roxarsone and related N-substituted phenylarsonic acid derivatives under anaerobic conditions. The results demonstrate that roxarsone is rapidly transformed in the absence of oxygen to the corresponding aromatic amine, 4-hydroxy-3-aminophenylarsonic acid (HAPA). The formation of HAPA is attributable to the facile reduction of the nitro group. Electron-donating substrates, such as hydrogen gas, glucose, and lactate, stimulated the rate of nitro group reduction, indicating a microbial role. During long-term incubations, HAPA and the closely related 4-aminophenylarsonic acid (4-APA) were slowly biologically eliminated by up to 99% under methanogenic and sulfate-reducing conditions, whereas little or no removal occurred in heat-killed inoculum controls. Arsenite and, to a lesser extent, arsenate were observed as products of the degradation. Freely soluble forms of the inorganic arsenical species accounted for 19-28% of the amino-substituted phenylarsonic acids removed. This constitutes the first report of a biologically catalyzed rupture of the phenylarsonic group under anaerobic conditions.
authors.affiliation: Department of Chemical and Environmental Engineering, University of Arizona, Arizona, P.O. Box 210011, Tucson, Arizona 85721-011, USA.
authors.forename: Irail
authors.initials: I
authors.lastname: Cortinas
authors.forename: Jim A
authors.initials: JA
authors.lastname: Field
authors.forename: Mike
authors.initials: M
authors.lastname: Kopplin
authors.forename: John R
authors.initials: JR
authors.lastname: Garbarino
authors.forename: A Jay
authors.initials: AJ
authors.lastname: Gandolfi
authors.forename: Reyes
authors.initials: R
authors.lastname: Sierra-Alvarez
mesh_terms: D001151:Arsenic / Q000633:toxicity; D001152:Arsenicals / Q000032:analysis* / Q000737:chemistry; D018053:Arsenites / Q000032:analysis; D001421:Bacteria, Anaerobic / Q000378:metabolism; D001673:Biodegradation, Environmental; D001711:Biotransformation; D002384:Catalysis; D004583:Electrons; D004784:Environmental Monitoring; D006358:Hot Temperature; D012037:Refuse Disposal; D012406:Roxarsone / Q000032:analysis*; D012989:Soil Pollutants; D014865:Waste Disposal, Fluid; D014873:Water Pollutants
chemical_list: C511221:4-hydroxy-3-aminophenylarsonic acid; D001152:Arsenicals; D018053:Arsenites; D012989:Soil Pollutants; D014873:Water Pollutants; D012406:Roxarsone; C015001:arsenite; D001151:Arsenic