Differential Degradation of Nonylphenol Isomers by Sphingomonas xenophaga Bayram

Abstract

Sphingomonas xenophaga Bayram, isolated from the activated sludge of a municipal wastewater treatment plant, was able to utilize 4-(1-ethyl-1,4-dimethylpentyl)phenol, one of the main isomers of technical nonylphenol mixtures, as a sole carbon and energy source. The isolate degraded 1 mg of 4-(1-ethyl-1,4-dimethylpentyl)phenol/ml in minimal medium within 1 week. Growth experiments with five nonylphenol isomers showed that the three isomers with quaternary benzylic carbon atoms [(1,1,2,4-tetramethylpentyl)phenol, 4-(1-ethyl-1,4-dimethylpentyl)phenol, and 4-(1,1-dimethylheptyl)phenol] served as growth substrates, whereas the isomers containing one or two hydrogen atoms in the benzylic position [4-(1-methyloctyl)phenol and 4-nnonylphenol] did not. However, when the isomers were incubated as a mixture, all were degraded to a certain degree. Differential degradation was clearly evident, as isomers with more highly branched alkyl side chains were degraded much faster than the others. Furthermore, the C 9 alcohols 2,3,5-trimethylhexan-2-ol, 3,6-dimethylheptan-3-ol, and 2-methyloctan-2-ol, derived from the three nonylphenol isomers with quaternary benzylic carbon atoms, were detected in the culture fluid by gas chromatography-mass spectrometry, but no analogous metabolites could be found originating from 4-(1-methyloctyl)phenol and 4-n-nonylphenol. We propose that 4-(1-methyloctyl)phenol and 4-n-nonylphenol were cometabolically transformed in the growth experiments with the mixture but that, unlike the other isomers, they did not participate in the reactions leading to the detachment of the alkyl moiety. This hypothesis was corroborated by the observed accumulation in the culture fluid of an as yet unidentified metabolite derived from 4-(1-methyloctyl)phenol.

A Novel Metabolic Pathway for Degradation of 4-Nonylphenol Environmental Contaminants by Sphingomonas xenophaga Bayram

“…However, the latter isomers were cometabolically transformed in experiments in which growth isomers were present. Furthermore, differential degradation was clearly evident because isomers with a more highly branched alkyl side chain were degraded much faster than those with less complex branching (10).…”

“…Growth experiments with strain Bayram showed that nonylphenol isomers with a quaternary carbon atom served as growth substrates, whereas the isomers containing one or two hydrogen atoms in benzylic position did not (10). However, the latter isomers were cometabolically transformed in experiments in which growth isomers were present.…”

“…1A) and most likely do not further metabolize these alcohols (10,11,16). However, these bacteria seem to be able to completely mineralize the aromatic moiety of those nonylphenol isomers that serve as growth substrates (10,11).…”

Molecular multi‐effect screening of environmental pollutants using the MolDarT

“…The positive control for rag1 was CdCl 2 (Fluka), and for cyp1a1 1,5-dimethylnaphthalene (DMN; Fluka) was used. Exposure experiments were carried out using bisphenol A (BPA), 17b-estradiol (E2), and 17a-ethinylestradiol (EE2; Sigma-Aldrich; Buchs, Switzerland), atrazine and cyproconazol (Dr. Ehrenstorfer; Augsburg, Germany), and nonylphenol (NP) isomer 19 (4-NP 112; 4-(1-ethyl-1,4-dimethylpentyl)phenol; a generous gift from F. Gabriel, custom made; Gabriel et al, 2005).…”

Functional and transcriptional analyses of the initial oxygenase genes for acenaphthene degradation from Sphingomonas sp. strain A4

“…They are attracting interest as a result of their high potential for bioremediation. In recent years, many Sphingomonas strains, which have been isolated from a variety of contaminated environments, have been described with respect to their ability to degrade xenobiotics and aromatic compounds, such as biphenyl (Fredrickson et al, 1995), dibenzo-p-dioxin (Wittich et al, 1992), carbazole (Habe et al, 2002), tetralin (Hernáez et al, 1999), pentachlorophenol (Saber & Crawford, 1985), 4-nonylphenol (Gabriel et al, 2005), c-hexachlorocyclohexane (Imai et al, 1989) and herbicides (Adkins, 1999;Kohler, 1999). In addition, Sphingomonas strains are often isolated from contaminated soils because of their ability to degrade polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous environmental pollutants with toxic, mutagenic and carcinogenic properties (Bastiaens et al, 2000;Khan et al, 1996;Mueller et al, 1990;Pinyakong et al, 2000).…”