Pathway Dependent Isotopic Fractionation during Aerobic Biodegradation of 1,2-Dichloroethane
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- 作者：Sarah K. Hirschorn ; M. Joyce Dinglasan ; Martin Elsner ; Silvia A. Mancini ; Georges Lacrampe-Couloume ; Elizabeth A. Edwards ; and Barbara Sherwood Lollar
- 刊名：Environmental Science & Technology
- 出版年：2004
- 出版时间：September 15, 2004
- 年：2004
- 卷：38
- 期：18
- 页码：4775 - 4781
- 全文大小：112K
- 年卷期：v.38,no.18(September 15, 2004)
- ISSN：1520-5851
文摘
1,2-Dichloroethane (1,2-DCA) is a widespread groundwatercontaminant known to be biodegradable under aerobicconditions via enzymatic oxidation or hydrolytic dehalogenation reactions. Current literature reports that stablecarbon isotope fractionation of 1,2-DCA during aerobicbiodegradation is large and reproducible (-27 to -33”).In this study, a significant variation in the magnitude of stablecarbon isotope fractionation during aerobic biodegradationwas observed. Biodegradation in experiments involvingmicrocosms, enrichment cultures, and pure microbial culturesproduced a consistent bimodal distribution of enrichmentfactors (
) with one mean centered on -3.9 ± 0.6” andthe other on -29.2 ± 1.9”. Reevaluation of in termsof kinetic isotope effects 12k/13k gave values of 12k/13k =1.01 and 1.06, which are typical of oxidation and hydrolyticdehalogenation (SN2) reactions, respectively. The bimodaldistribution is therefore consistent with the microbialdegradation of 1,2-DCA by two separate enzymatic pathways.This interpretation is further supported in this study byexperiments with pure strains of Xanthobacter autotrophicusGJ10, Ancylobacter aquaticus AD20, and Pseudomonassp. Strain DCA1 for which the enzymatic degradation pathwaysare well-known. A small fractionation of -3.0” wasmeasured for 1,2-DCA degradation by Pseudomonas sp.Strain DCA1 (monooxygenase enzyme), while degradationby the hydrolytic dehalogenase enzyme by the othertwo pure strains was characterized by fractionation of-32.3”.
) with one mean centered on -3.9 ± 0.6” andthe other on -29.2 ± 1.9”. Reevaluation of in termsof kinetic isotope effects 12k/13k gave values of 12k/13k =1.01 and 1.06, which are typical of oxidation and hydrolyticdehalogenation (SN2) reactions, respectively. The bimodaldistribution is therefore consistent with the microbialdegradation of 1,2-DCA by two separate enzymatic pathways.This interpretation is further supported in this study byexperiments with pure strains of Xanthobacter autotrophicusGJ10, Ancylobacter aquaticus AD20, and Pseudomonassp. Strain DCA1 for which the enzymatic degradation pathwaysare well-known. A small fractionation of -3.0” wasmeasured for 1,2-DCA degradation by Pseudomonas sp.Strain DCA1 (monooxygenase enzyme), while degradationby the hydrolytic dehalogenase enzyme by the othertwo pure strains was characterized by fractionation of-32.3”.