Abstract
Nonylphenols (NPs) have been proved to be accumulated in sediments in aquatic environments as the degradation products of non-ionic surfactants and show endocrine disruptive activity to living organisms. To elucidate the biodegradation mechanisms for NPs, we isolated five NP-degrading bacteria from activated sludge using a commercial mixture of NP isomers (Kanto Kagaku, Tokyo) as a sole carbon source. Analysis of the partial 16S rDNA sequences of the isolates revealed that one strain is a Sphingomonas sp. and other four strains are Pseudomonas spp. On a minimal medium plate containing the NP mixture, the Sphingomonas strain, named strain NP5, formed a clear zone (halo), indicating that it degraded most of the NP isomers dispersed in the plate. In order to confirm the biodegradability for the NP isomers, a NP degradation test was carried out using the cell suspension of strain NP5. GC/MS analysis showed that at least 14 NP isomers contained in the mixture disappeared completely after 7 d- incubation and some alcohols with nine carbons were detected as the metabolites. This result indicates that strain NP5 has a broad degradation range for NP isomers and release of the alkyl-chain of NP might occur during the degradation.
