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Effects of alkyl chain branching on the biotransformation of naphthenic acids

Smith, BE and Lewis, CA and Belt, ST and Whitby, C and Rowland, SJ (2008) 'Effects of alkyl chain branching on the biotransformation of naphthenic acids.' Environmental Science and Technology, 42 (24). 9323 - 9328. ISSN 0013-936X

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The rapid expansion of the oil sands industry has seen a concomitant expansion of the production of associated waste containing toxic naphthenic acids (NAs). Bioremediation of such waste is thus an important goal, but the mechanisms of biodegradation are still poorly understood, despite recent advances. Many oil sands NAs are resistant to biodegradation, and alkyl side chain branching has been invoked as an explanation. To investigate this hypothesis we examined the biotransformation by a sedimentary bacterial community of novel, synthetic, surrogate NAs (butylcyclohexylbutanoic acids (BCHBAs)) with variously branched butyl side chains (n- through t-) and unbranched alkanoate groups, plus one (4-(4′-isobutylcyclohexyl)pentanoic acid (iso-BCHPA)), with both branched butyl and branched alkanoate chains. Sediment microbial populations were inoculated into media containing the individual surrogate NAs, and gas chromatography-mass spectrometry (GC-MS) was used to determine the extent of biotransformation. Biotransformation decreased as NA side chain branching increased. For example, over 97% of the n-BCHBA with the nonbranched alkyl side chain was transformed in 30 days compared to the tert-BCHBA with the most highly branched side chain where only 2.5% was transformed. Both the iso-BCHBA and sec-BCHBA had intermediate transformation rates with about 77% and 47% transformed respectively after 30 days. The metabolites were identified as butylcyclohexylethanoic acids in each case, indicating beta-oxidation of the alkanoate substituents. The iso-BCHPA with both chains branched was resistant to degradation. The results are thus consistent with earlier hypotheses for the resistance of oil sands NAs. Identification of bacteria capable of oxidizing such branched alkyl chains-or of attacking the cyclic rings of NAs, may be important if bioremediation of oil sands NAs is to be achieved. © 2008 American Chemical Society.

Item Type: Article
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health > Life Sciences, School of
Depositing User: Jim Jamieson
Date Deposited: 23 Sep 2011 14:54
Last Modified: 28 Aug 2019 10:16

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