Variations in 13C/12C and D/H enrichment factors of aerobic bacterial fuel oxygenate degradation

Abstract

8 pages, 3 figures.-- PMID: 17410802 [PubMed].-- Printed version published on Mar 15, 2007.Supplementary information (Suppl. figure S1, 6 pages) available at: http://pubs.acs.org/doi/suppl/10.1021/es0616175/suppl_file/es0616175si20061213_010401.pdfReliable compound-specific isotope enrichment factors are needed for a quantitative assessment of in situ biodegradation in contaminated groundwater. To obtain information on the variability on carbon and hydrogen enrichment factors (εC, εH) the isotope fractionation of methyl tertiary (tert-) butyl ether (MTBE) and ethyl tert-butyl ether (ETBE) upon aerobic degradation was studied with different bacterial isolates. Methylibium sp. R8 showed a carbon and hydrogen isotope enrichment upon MTBE degradation of -2.4 ± 0.1 and -42 ± 4‰, respectively, which is in the range of previous studies with pure cultures (Methylibium petroleiphilum PM1) as well as mixed consortia. In contrast, εC of the β-proteobacterium L108 (-0.48 ± 0.05‰) and Rhodococcus ruber IFP 2001 (-0.28 ± 0.06‰) was much lower and hydrogen isotope fractionation was negligible (εH < -0.2‰). The varying isotope fractionation pattern indicates that MTBE is degraded by different mechanisms by the strains R8 and PM1 compared to L108 and IFP 2001. The carbon and hydrogen isotope fractionation of ETBE by L108 (εC = - 0.68 ± 0.06‰ and εH = -14 ± 2‰) and IFP 2001 εC = -0.8 ± 0.1‰ and εH = -11 ± 4‰) was very similar and seemed slightly higher than the fractionation observed upon MTBE degradation by the same strains. The low carbon and hydrogen enrichment factors observed during MTBE and ETBE degradation by L108 and IFP 2001 suggest a hydrolysis-like reaction type of the ether bond cleavage compared to oxidation of the alkyl group as suggested for the strains PM1 and R8. The variability of carbon and hydrogen enrichment factors should be taken into account when interpreting isotope pattern of fuel oxygenates with respect to biodegradation in contamination plumes.We thank Ursula Günther, Monika Neytschev, and Cornelia Schumann for technical support at the UFZ. We are also grateful to Erik Arvin (Technical University of Denmark, Lyngby, Denmark) and Françoise Fayolle-Guichard and Frédéric Monot (Institute Françoise du Petrole, Cedex, France) for providing an enrichment culture and strain IFP 2001, respectively. Part of the work was financed by the German Federal Ministry of Education and Research (02 WN 0348) within the METLEN project and by the UFZ (SAFIRA). The fellowship of Mònica Rosell was supported by AXIOM-Marie Curie Host Fellowships For Early Stage Training (EST) (contract MEST-CT-2004-8332) and Catalonian fellowship for research in an outsider country (2005 BE 00008) in the framework of AXIOM project "Assessment of in situ Transformation of Xenobiotic Organic Material". She also received a regular PhD grant from Department of Universities, Research and Information Society of Generalitat de Catalunya (expedient 2005FIR 00348).Peer reviewe