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Evidence of Substantial Carbon Isotope Fractionation among Substrate, Inorganic Carbon, and Biomass during Aerobic Mineralization of 1,2-Dichloroethane by <i>Xanthobacter autotrophicus</i>
Auteur(s)
Date de parution
2000
In
Applied and Environmental Microbiology, American Society for Microbiology, 2000/66/11/4870-4876
Résumé
Carbon isotope fractionation during aerobic mineralization of 1,2-dichloroethane (1,2-DCA) by <i>Xanthobacter autotrophicus</i> GJ10 was investigated. A strong enrichment of <sup>13</sup>C in residual 1,2-DCA was observed, with a mean fractionation factor α ± standard deviation of 0.968 ± 0.0013 to 0.973 ± 0.0015. In addition, a large carbon isotope fractionation between biomass and inorganic carbon occurred. A mechanistic model that links the fractionation factor α to the rate constants of the first catabolic enzyme was developed. Based on the model, it was concluded that the strong enrichment of <sup>13</sup>C in 1,2-DCA arises because the first irreversible step of the initial enzymatic transformation of 1,2-DCA consists of an S<sub>N</sub>2 nucleophilic substitution. S<sub>N</sub>2 reactions are accompanied by a large kinetic isotope effect. The substantial carbon isotope fractionation between biomass and inorganic carbon could be explained by the kinetic isotope effect associated with the initial 1,2-DCA transformation and by the metabolic pathway of 1,2-DCA degradation. Carbon isotope fractionation during 1,2-DCA mineralization leads to 1,2-DCA, inorganic carbon, and biomass with characteristic carbon isotope compositions, which may be used to trace the process in contaminated environments.
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Resource Types::text::journal::journal article
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