No abstract

We investigated the ability of Trametes versicolor and Pycnoporous cinnabarinus to metabolize triclosan. T. versicolor produced three metabolites, 2-O-(2,4,4-trichlorodiphenyl ether)-␤-D-xylopyranoside, 2-O-(2,4,4-trichlorodiphenyl ether)-␤-D-glucopyranoside, and 2,4-dichlorophenol. P. cinnabarinus converted triclosan to 2,4,4-trichloro-2-methoxydiphenyl ether and the glucoside conjugate known from T. versicolor. The conjugates showed a distinctly lower cytotoxic and microbicidal activity than triclosan did.Triclosan (2,4,4Ј-trichloro-2Ј-hydroxydiphenyl ether; synonym, Irgasan DP 300) has been used as an antimicrobial compound in deodorants (6), soaps, and dentifrices (2, 8, 36) for many years. The mode of action of triclosan has, however, remained unclear. Recently, it was shown that triclosan blocks one step in bacterial fatty acid synthesis (20,24,25). Due to its widespread use, triclosan and some of its derivatives can be detected in the environment (22,26,27). The chemical structure of triclosan is related to many compounds which are wellknown as xenobiotics, such as halogenated diphenyl ethers. Though some reports on the transformation of halogenated diphenyl ether compounds by bacteria are available (21, 30), triclosan itself was not metabolized by the strains tested (31) or by Rhodococcus chlorophenolicus, which can methylate several other chlorinated hydroxydiphenyl ethers (34). Several hydroxylated metabolites, as well as 2,4-dichlorophenol and 4-chlorocatechol, are formed from triclosan by rats (33), while guinea pigs mostly form glucuronide conjugates (3). No reports exist concerning the degradation of triclosan by fungi. The white rot fungi Trametes versicolor and Pycnoporus cinnabarinus are capable of transforming diphenyl ethers, like 4-chlorodiphenyl ether, up to ring cleavage (10, 11). Hydroxylated biarylic ethers are transformed to oligomerization products by laccases secreted by these strains (13). In this paper we describe some biotransformation reactions of triclosan by the white rot fungi T. versicolor and P. cinnabarinus.The strains T. versicolor SBUG-M 1050, T. versicolor DSM 11269, T. versicolor DSM 11309, and P. cinnabarinus SBUG-M 1044 were cultivated in a nitrogen-rich (8 mM) medium. The cultures for transformation were prepared with 0.25 mM (wt/ vol) triclosan (Mallinckrodt-Baker, Griesheim, Germany) and inoculated and incubated as described previously (10, 11).Cell extracts were prepared from a 3-day culture of T. versicolor, harvested by centrifugation, and washed twice with 50 mM ice-cold Tris-HCl buffer (pH 7.5). Cells were broken at 1,000 lb/in 2 using a French press (SLM Amnico, Rochester, N.Y.) and were immediately resuspended in Tris-HCl buffer. The cell extracts (4 ml, approximately 5 mg of protein ml Ϫ1 ) were incubated at 30°C for 24 h with 2.88 mg of triclosan and 1 mg each of UDP-xylose, UDP-glucose, and UDP-glucuronic acid (Sigma, Deisenhofen, Germany).Analysis of metabolites in culture supernatants and purification of intermediates were done by high-performance liquid ...

We have investigated the transformation of chlorinated hydroxybiphenyls by laccase produced by Pycnoporus cinnabarinus. The compounds used were transformed to sparingly water-soluble colored precipitates which were identified by gas chromatography-mass spectrometry as oligomerization products of the chlorinated hydroxybiphenyls. During oligomerization of 2-hydroxy-5-chlorobiphenyl and 3-chloro-4-hydroxybiphenyl, dechlorinated COC-linked dimers were formed, demonstrating the dehalogenation ability of laccase. In addition to these nonhalogenated dimers, both monohalogenated and dihalogenated dimers were identified.

Laccase, a ligninolytic enzyme, was secreted by each of the white rot fungi Trametes versicolor and Pycnoporus cinnabarinus during growth in a nitrogen-rich medium under agitated conditions. After addition of 2-hydroxydibenzofuran to cell-free supernatants of the cultures, yellow precipitates were formed. These precipitates were poorly soluble in water and therefore readily separated from the supernatant. The products formed were more hydrophobic than the substrate, as indicated by their longer retention times on a reverse phase high-performance liquid chromatography column. Mass spectrometric analysis of the purified products indicated the formation of oligomers. Analysis of the mixture of products by gas chromatography and mass spectrometry after derivatization with diazomethane suggested the formation of at least three dimeric and nine trimeric products. Carbon-carbon and carbon-oxygen bonds were identified in the dimers and trimers, respectively. The nuclear magnetic resonance spectrum of the main dimer suggested coupling of the two monomers at the carbon one position.

Cells of the white rot fungus Pycnoporus cinnabarinus grown in glucose were able to hydroxylate biphenyl and diphenyl ether, although growth was inhibited by these substrates at concentrations above 250 microM. 2- and 4-Hydroxybiphenyl were detected as products of biphenyl metabolism and 2- and 4-hydroxydiphenyl ether as products of diphenyl ether metabolism in the culture media. After addition of 2-hydroxydiphenyl ether and 2-hydroxybiphenyl to cell-free supernatants containing laccase as the only ligninolytic enzyme, different coloured precipitates were formed. HPLC analysis revealed the formation of additional hydrophobic metabolites with one major product per transformation. Mass spectrometric analysis of the methyl derivatives of the polymer mixture indicated dimers and trimers with different binding types. The main products were identified as dimers with carbon-carbon bonds in para-position to the hydroxyl group of the monomers by mass spectroscopy and nuclear magnetic resonance spectroscopy.