Isotopic fractionation of methyl tert-butyl ether suggests different initial reaction mechanisms during aerobic biodegradation

Jennifer R. Mckelvie, Michael R. Hyman, Martin Elsner, Christy Smith, Denise M. Aslett, Georges Lacrampe-Couloume, Barbara Sherwood Lollar

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

Carbon isotopic enrichment factors (εC) measured during cometabolic biodegradation of methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME) by Pseudonocardia tetrahydrofuranoxydans strain K1 were -2.3 ±0.2%, -1.7 (0.2%, and -1.7 ±0.3%, respectively. The measured carbon apparent kinetic isotope effect was 1.01 for all compounds, consistent with the expected kinetic isotope effects for both oxidation of the methoxy (or ethoxy) group and enzymatic S N1 biodegradation mechanisms. Significantly, δ 13C measurements of the tert-butyl alcohol and tert-amyl alcohol products indicated that the tert-butyl and tert-amyl groups do not participate in the reaction and confirmed that ether biodegradation by strain K1 involves oxidation of the methoxy (or ethoxy) group. Measured hydrogen isotopic enrichment factors (εH) were -100 ± 10%, -73 ± 7%, and -72 ± 2% for MTBE, ETBE, and TAME respectively. Previous results reported for aerobic biodegradation of MTBE by Methylibium petroleiphilum PM1 and Methylibium R8 showed smaller εH values (-35% and -42%, respectively). Plots of Δ 2H/ Δ 13C show different slopes for strain K1 compared with strains PM1 and R8, suggesting that different mechanisms are utilized by K1 and PM1/R8 during aerobic MTBE biodegradation.

Original languageEnglish
Pages (from-to)2793-2799
Number of pages7
JournalEnvironmental Science and Technology
Volume43
Issue number8
DOIs
StatePublished - 15 Apr 2009
Externally publishedYes

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