Carbon and Nitrogen Isotope Effects Associated with the Dioxygenation of Aniline and Diphenylamine

• DOI: 10.1021/es303043t
• Publication Date: 2012-09-27T21:32:12Z
• Authors: Sarah G. Pati; Kwanghee Shin; Marita Skarpeli-L...; Jakov Bolotin; Soren N. Eustis; Jim C. Spain; Thomas B. Hofstetter
• Keywords: Carbon Isotopes; 0303 health sciences; Aniline Compounds; Nitrogen Isotopes; Burkholderia; Diphenylamine; Oxides; Dioxygenases; 03 medical and health sciences; Biodegradation, Environmental; Manganese Compounds; 13. Climate action; Soil Pollutants; Oxidation-Reduction

Dioxygenation of aromatic rings is frequently the initial step of biodegradation of organic subsurface pollutants. This process can be tracked by compound-specific isotope analysis to assess the extent of contaminant transformation, but the corresponding isotope effects, especially for dioxygenation of N-substituted, aromatic contaminants, are not well understood. We investigated the C and N isotope fractionation associated with the biodegradation of aniline and diphenylamine using pure cultures of Burkholderia sp. strain JS667, which can biodegrade both compounds, each by a distinct dioxygenase enzyme. For diphenylamine, the C and N isotope enrichment was normal with ε(C)- and ε(N)-values of -0.6 ± 0.1‰ and -1.0 ± 0.1‰, respectively. In contrast, N isotopes of aniline were subject to substantial inverse fractionation (ε(N) of +13 ± 0.5‰), whereas the ε(C)-value was identical to that of diphenylamine. A comparison of the apparent kinetic isotope effects for aniline and diphenylamine dioxygenation with those from abiotic oxidation by manganese oxide (MnO(2)) suggest that the oxidation of a diarylamine system leads to distinct C-N bonding changes compared to aniline regardless of reaction mechanism and oxidant involved. Combined evaluation of the C and N isotope signatures of the contaminants reveals characteristic Δδ(15)N/Δδ(13)C-trends for the identification of diphenylamine and aniline oxidation in contaminated subsurfaces and for the distinction of aniline oxidation from its formation by microbial and/or abiotic reduction of nitrobenzene.