Anaerobic biodegradation of 4-alkylphenols in a paddy soil microcosm supplemented with nitrate

Abstract

Anaerobic degradation of phenol, p-cresol, 4- n-propylphenol ( n-PP), 4- i-propylphenol ( i-PP), 4- n-butylphenol ( n-BP) and 4- sec-butylphenol ( sec-BP) was observed in a paddy soil supplemented with nitrate. We detected the metabolites 4′-hydroxypropiophenone (HPP) from n-PP, 4- i-propenylphenol from i-PP, and 4-(1-butenyl)phenol and 4′-hydroxybutyrophenone (HBP) from n-BP. Compared with the original soils, Betaproteobacteria became predominant in the microcosm during the degradation of phenol and p-cresol whereas no remarkable change was observed in the community degrading propylphenols and butylphenols. The microcosm, however, did not degrade 4- t-butylphenol ( t-BP), 4- t-octylphenol ( t-OP) and 4- n-octylphenol ( n-OP). Paddy soil supplemented with sulfate or iron (III) as electron acceptors did not degrade phenol and 4-alkylphenols with the exception of the degradation of p-cresol in sulfate-reducing conditions. It was demonstrated for the first time that anaerobic microbial degradation of alkylphenols, in a paddy soil supplemented with nitrate as an electron acceptor, occurred via oxidation of the alpha carbon in the alkyl chain.