Biotransformation of 3,5-dibromo-4-hydroxybenzonitrile under denitrifying, FE(III)-reducing, sulfidogenic, and methanogenic conditions

Victoria K. Knight, Mitchell H. Berman, Max M. Häggblom

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11 Scopus citations


Bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) is a halogenated aromatic nitrile herbicide used on a variety of crops for the postemergence control of annual broad-leaved weeds. The anaerobic biodegradability of bromoxynil and its aerobic transformation product, 3,5-dibromo-4-hydroxybenzoate, were examined in enrichment cultures established with anaerobic sediment under denitrifying, Fe(III)-reducing, sulfidogenic, and methanogenic conditions. Bromoxynil (100 μM) was depleted in 20 to 30 d in the methanogenic, sulfidogenic, and Fe(III)-reducing enrichments but was stable under denitrifying conditions. The 3,5-dibromo4-hydroxybenzoate (100 μM) was depleted within 20 to 35 d under all four anaerobic conditions. Both compounds were stable in sterile controls. Bromoxynil and 3,5-dibromo-4-hydroxybenzoate were readily utilized upon respiking of the cultures. During utilization of bromoxynil, stoichiometric release of bromide was observed with transient accumulation of metabolites identified as bromocyanophenol, cyanophenol, and phenol. Bromoxynil heptanoate and octanoate were rapidly hydrolyzed to bromoxynil, which was further degraded. These results indicate that bromoxynil and 3,5-dibromo-4-hydroxybenzoate are degraded under different anaerobic conditions. Anaerobic degradation of bromoxynil proceeds via reductive debromination to 4-cyanophenol, which is further transformed to phenol and can ultimately be degraded to carbon dioxide.

Original languageEnglish (US)
Pages (from-to)540-544
Number of pages5
JournalEnvironmental Toxicology and Chemistry
Issue number3
StatePublished - Mar 1 2003

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Health, Toxicology and Mutagenesis


  • Anaerobic transformation
  • Brominated nitrile herbicide
  • Dehalogenation

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