Title

Isotope Analysis As a Natural Reaction Probe to Determine Mechanisms of Biodegradation of 1,2-Dichloroethane

Publication Date

7-1-2007

Document Type

Article

Abstract

1,2-Dichloroethane (1,2-DCA), a chlorinated aliphatic hydrocarbon, is a well-known groundwater contaminant. In this study, fractionation of stable carbon isotope values of 1,2-DCA during biodegradation was used as a novel reaction probe to provide information about the mechanism of 1,2-DCA biodegradation under both aerobic (O2-reducing) and anaerobic (NO3-reducing) conditions. Under O2-reducing conditions, an isotopic enrichment value ( ε) of −25.8 ± 1.1‰ (±95% confidence intervals) was measured for the enrichment culture. Under NO3-reducing conditions, an ε-value of −25.8 ± 3.5‰ was measured. The microbial culture produced isotopic enrichment values ( ε) that are not only large and reproducible, but also are the same whether O2 or NO3 was used as an electron acceptor. Combining data measured under both O2- and NO3-reducing conditions, an isotopic enrichment value ( ε) of −25.8 ± 1.6‰ is measured for the microbial culture during 1,2-DCA degradation. The ε-value can be converted into a kinetic isotope effect (KIE) value to relate the observed isotopic fractionation to the mechanism of degradation. This KIE value (1.05) is consistent with degradation via hydrolytic dehalogenation under both electron-accepting conditions. This study demonstrates the added value of compound-specific isotope analysis not only as a technique to verify the occurrence and extent of biodegradation in the field, but also as a natural reaction probe to provide insight into the enzymatic mechanism of contaminant degradation.

Publication Title

Environmental Microbiology

Volume

9

Issue

7

First Page

1651

Last Page

1657

DOI

10.1111/j.1462-2920.2007.01282.x

Version

pre-print, post-print with restrictions

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