title: Carbon Stable Isotope Fractionation of Sulfamethoxazole during Biodegradation by Microbacterium sp. Strain BR1 and upon Direct Photolysis.
abstract: Carbon isotope fractionation of sulfamethoxazole (SMX) during biodegradation by Microbacterium sp. strain BR1 (ipso-hydroxylation) and upon direct photolysis was investigated. Carbon isotope signatures (δ(13)C) of SMX were measured by LC-IRMS (liquid chromatography coupled to isotope ratio mass spectrometry). A new LC-IRMS method for the SMX metabolite, 3-amino-5-methylisoxazole (3A5MI), was established. Carbon isotope enrichment factors for SMX (ε(C)) were -0.6 ± 0.1‰ for biodegradation and -2.0 ± 0.1‰ and -3.0 ± 0.2‰ for direct photolysis, at pH 7.4 and pH 5, respectively. The corresponding apparent kinetic isotope effects (AKIE) for ipso-hydroxylation were 1.006 ± 0.001; these fall in the same range as AKIE in previously studied hydroxylation reactions. The differences in SMX and 3A5MI fractionation upon biotic and abiotic degradation suggest that compound specific stable isotope analysis (CSIA) is a suitable method to distinguish SMX reaction pathways. In addition, the study revealed that the extent of isotope fractionation during SMX photolytic cleavage is pH-dependent.
authors.affiliation: †Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Saxony, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Birkigt
authors.affiliation: †Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Saxony, Germany.
authors.forename: Tetyana
authors.initials: T
authors.lastname: Gilevska
authors.affiliation: ‡Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4132 Muttenz, Basel-Landschaft, Switzerland.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ricken
authors.affiliation: †Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Saxony, Germany.
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
authors.affiliation: §Department of Chemistry, University of Torino, 10125 Torino, Torino, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Vione
authors.affiliation: ‡Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4132 Muttenz, Basel-Landschaft, Switzerland.
authors.forename: Philippe F-X
authors.initials: PF
authors.lastname: Corvini
authors.affiliation: †Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, 04318 Leipzig, Saxony, Germany.
authors.forename: Ivonne
authors.initials: I
authors.lastname: Nijenhuis
authors.affiliation: ‡Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences and Arts Northwestern Switzerland, 4132 Muttenz, Basel-Landschaft, Switzerland.
authors.forename: Danuta
authors.initials: D
authors.lastname: Cichocka
mesh_terms: D000192:Actinomycetales / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000378:metabolism*; D010782:Photolysis; D013420:Sulfamethoxazole / Q000032:analysis / Q000378:metabolism*
chemical_list: D002247:Carbon Isotopes; D013420:Sulfamethoxazole