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Applied and Environmental Microbiology, July 2009, p. 4398-4409, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.00139-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Quantification of the Influence of Extracellular Laccase and Intracellular Reactions on the Isomer-Specific Biotransformation of the Xenoestrogen Technical Nonylphenol by the Aquatic Hyphomycete Clavariopsis aquatica

Claudia Martin,¹ Philippe F. X. Corvini,² Ralph Vinken,³ Charles Junghanns,¹ Gudrun Krauss,¹ and Dietmar Schlosser^1*

UFZ, Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, 04318 Leipzig, Germany,¹ Institute for Ecopreneurship, School of Life Sciences, University of Applied Sciences Northwestern Switzerland, 4132 Muttenz, Switzerland,² Dr. Knoell Consult GmbH, 51377 Leverkusen, Germany³

Received 20 January 2009/ Accepted 29 April 2009

The aquatic hyphomycete Clavariopsis aquatica was used to quantify the effects of extracellular laccase and intracellular reactions on the isomer-specific biotransformation of technical nonylphenol (t-NP). In laccase-producing cultures, maximal removal rates of t-NP and the isomer 4-(1-ethyl-1,4-dimethylpentyl)phenol (NP112) were about 1.6- and 2.4-fold higher, respectively, than in laccase-lacking cultures. The selective suppression of either laccase or intracellular reactions resulted in essentially comparable maximal removal rates for both compounds. Evidence for an unspecific oxidation of t-NP isomers was consistently obtained from laccase-expressing fungal cultures when intracellular biotransformation was suppressed and from reaction mixtures containing isolated laccase. This observation contrasts with the selective degradation of t-NP isomers by bacteria and should prevent the enrichment of highly estrogenic isomers in remaining t-NP. In contrast with laccase reactions, intracellular fungal biotransformation caused a significant shift in the isomeric composition of remaining t-NP. As a result, certain t-NP constituents related to more estrogenic isomers were less efficiently degraded than others. In contrast to bacterial degradation via ipso-hydroxylation, the substitution pattern of the quaternary -carbon of t-NP isomers does not seem to be very important for intracellular transformation in C. aquatica. As-yet-unknown intracellular enzymes are obviously induced by nonylphenols. Mass spectral data of the metabolites resulting from the intracellular oxidation of t-NP, NP112, and 4-(1-ethyl-1,3-dimethylpentyl)phenol indicate nonyl chain hydroxylation, further oxidation into keto or aldehyde compounds, and the subsequent formation of carboxylic acid derivatives. Further metabolites suggest nonyl chain desaturation and methylation of carboxylic acids. The phenolic moieties of the nonylphenols remained unchanged.

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* Corresponding author. Mailing address: Department of Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Permoserstrasse 15, 04318 Leipzig, Germany. Phone: 49 341 235 1329. Fax: 49 341 235 2247. E-mail: dietmar.schlosser{at}ufz.de

Published ahead of print on 8 May 2009.

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Applied and Environmental Microbiology, July 2009, p. 4398-4409, Vol. 75, No. 13
0099-2240/09/$08.00+0     doi:10.1128/AEM.00139-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.