Insights into enzyme kinetics of chloroethane biodegradation using compound specific stable isotopes.

While compound specific isotope analysis (CSIA) has been used extensively to investigate remediation of chlorinated ethenes, to date considerably less information is available on its applicability to chlorinated ethanes. In this study, biodegradation of 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethane (1,1-DCA) was carried out by a Dehalobacter-containing mixed culture. Carbon isotope fractionation factors (e) measured during whole cell degradation demonstrated that values for 1,1,1-TCA and 1,1-DCA (−1.8‰ and −10.5‰, respectively) were significantly smaller than values reported for abiotic reductive dechlorination of these same compounds. Similar results were found in experiments degrading these two priority pollutants by cell free extracts (CFE) where values of −0.8‰ and −7.9‰, respectively, were observed. For 1,1,1-TCA in particular, the large kinetic isotope effect expected for cleavage of a C−Cl bond was almost completely masked during biodegradation by both whole cells and CFE. Comparison to ...