title: Enantioselective carbon stable isotope fractionation of hexachlorocyclohexane during aerobic biodegradation by Sphingobium spp.
abstract: Carbon isotope fractionation was investigated for the biotransformation of γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers of α-HCH using two aerobic bacterial strains: Sphingobium indicum strain B90A and Sphingobium japonicum strain UT26. Carbon isotope enrichment factors (ε(c)) for γ-HCH (ε(c) = -1.5 ± 0.1 ‰ and -1.7 ± 0.2 ‰) and α-HCH (ε(c) = -1.0 ± 0.2 ‰ and -1.6 ± 0.3 ‰) were similar for both aerobic strains, but lower in comparison with previously reported values for anaerobic γ- and α-HCH degradation. Isotope fractionation of α-HCH enantiomers was higher for (+) α-HCH (ε(c) = -2.4 ± 0.8 ‰ and -3.3 ± 0.8 ‰) in comparison to (-) α-HCH (ε(c) = -0.7 ± 0.2 ‰ and -1.0 ± 0.6 ‰). The microbial fractionation between the α-HCH enantiomers was quantified by the Rayleigh equation and enantiomeric fractionation factors (ε(e)) for S. indicum strain B90A and S. japonicum strain UT26 were -42 ± 16% and -22 ± 6%, respectively. The extent and range of isomer and enantiomeric carbon isotope fractionation of HCHs with Sphingobium spp. suggests that aerobic biodegradation of HCHs can be monitored in situ by compound-specific stable isotope analysis (CSIA) and enantiomer-specific isotope analysis (ESIA). In addition, enantiomeric fractionation has the potential as a complementary approach to CSIA and ESIA for assessing the biodegradation of α-HCH at contaminated field sites.
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ , Permoserstraße 15, 04318, Leipzig, Germany.
authors.forename: Safdar
authors.initials: S
authors.lastname: Bashir
authors.forename: Anko
authors.initials: A
authors.lastname: Fischer
authors.forename: Ivonne
authors.initials: I
authors.lastname: Nijenhuis
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
mesh_terms: D000332:Aerobiosis; D001673:Biodegradation, Environmental; D001711:Biotransformation; D002247:Carbon Isotopes; D005591:Chemical Fractionation; D001556:Hexachlorocyclohexane / Q000737:chemistry* / Q000378:metabolism*; D045249:Sphingobacterium / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D002247:Carbon Isotopes; D001556:Hexachlorocyclohexane