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Journal of Biotechnology
157, No. 4, 2012; Pages: 490 - 498

Changes in iso- and n-alkane distribution during biodegradation of crude oil under nitrate and sulphate reducing conditions

Marion Hasinger, Kerstin E. Scherr, Tserennyam Lundaa, Leopold Bräuer, Clemens Zach, Andreas Paul Loibner

University of Natural Resources and Life Sciences Vienna, Department for Agrobiotechnology, Institute for Environmental Biotechnology, Konrad Lorenz Strasse 20, 3430 Tulln, Austria.


Crude oil consists of a large number of hydrocarbons with different susceptibility to microbial degradation. The influence of hydrocarbon structure and molecular weight on hydrocarbon biodegradation under anaerobic conditions is not fully explored. In this study oxygen, nitrate and sulphate served as terminal electron acceptors (TEAs) for the microbial degradation of a paraffin-rich crude oil in a freshly contaminated soil. During 185 days of incubation, alkanes from n-C11 to n-C39, three n- to iso-alkane ratios commonly used as weathering indicators and the unresolved complex mixture (UCM) were quantified and statistically analyzed.
The use of different TEAs for hydrocarbon degradation resulted in dissimilar degradative patterns for n- and iso-alkanes. While n-alkane biodegradation followed well-established patterns under aerobic conditions, lower molecular weight alkanes were found to be more recalcitrant than mid- to high-molecular weight alkanes under nitrate-reducing conditions. Biodegradation with sulphate as the TEA was most pronounced for long-chain (n-C32 to n-C39) alkanes. The observation of increasing ratios of n-C17 to pristane and of n-C18 to phytane provides first evidence of the preferential degradation of branched over normal alkanes under sulphate reducing conditions.
The formation of distinctly different n- and iso-alkane biodegradation fingerprints under different electron accepting conditions may be used to assess the occurrence of specific degradation processes at a contaminated site. The use of n- to iso-alkane ratios for this purpose may require adjustment if applied for anaerobic sites.

Keywords: Anaerobic biodegradation; Bioremediation; Long chain n-alkanes; Iso-alkanes; Crude oil; Hydrocarbon fingerprint; Terminal electron acceptors



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