Degradation of diphenyl ether herbicides by the lignin-degrading basidiomycete Coriolus versicolor

Abstract

Under ligninolytic conditions, the white-rot basidiomycete Coriolus versicolor metabolized chloronitrofen (2, 4, 6-trichloro-4'-nitrodiphenyl ether; CNP) and nitrofen (2, 4-dichloro-4'-nitrodiphenyl ether, NIP), which constitute the largest class of commercially produced diphenyl ether herbicides. The pathway of CNP degradation was elucidated by the identification of fungal metabolites upon addition of CNP and its metabolic intermediates. The metabolic pathway was initially branched to form four metabolites--2, 4, 6-trichloro-3-hydroxy-4'-nitrodiphenyl ether, 2, 4-dichloro-6-hydroxy-4'-nitrodiphenyl ether, NIP, and 2, 4, 6-trichloro-4'-aminodiphenyl ether--indicating the involvement of hydroxylation, oxidative dechlorination, reductive dechlorination, and nitro-reduction. Of these reactions, hydroxylation was relatively major compared to the others. Extracellular ligninolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase did not catalyze the oxidation of either CNP or NIP. Piperonyl butoxide, an inhibitor of cytochrome P450, suppressed fungal oxidation of CNP and NIP to their hydroxylated products. The inhibition resulted in increasing the amount of reductively dechlorinated and nitro-reduced products. These observations strongly suggest that basidiomycetes may possess a mechanism for a strict substrate recognition system and a corresponding metabolic response system to effectively degrade environmentally persistent aromatic compounds.

Unraveling the Detoxification Mechanism of 2,4-Dichlorophenol by Marine-Derived Mesophotic Symbiotic Fungi Isolated from Marine Invertebrates

“…Additionally, a marine-derived Trichoderma harzianum strain isolated from ascidian Didemnun ligulum could biotransform pentachlorophenol and produce pentachloroanisole and 2,3,4,6-tetrachloroanisole suggesting a reductive dehalogenation activity [31]. The white-rot fungus Coriolus versicolor followed different pathways for the transformation of the herbicide chloronitrofen—including hydroxylations, oxidative, and reductive dechlorination reactions [32].…”

Biochemical Characterization of CYP505D6, a Self-Sufficient Cytochrome P450 from the White-Rot Fungus Phanerochaete chrysosporium

“…W hite-rot fungi are capable of degrading a wide variety of recalcitrant aromatic compounds, including lignin and environmentally persistent pollutants (1)(2)(3)(4)(5)(6)(7)(8)(9). Fungal ligninolytic enzymes involved in the metabolism of aromatic compounds have been extensively studied (1,2).…”

“…Fungal ligninolytic enzymes involved in the metabolism of aromatic compounds have been extensively studied (1,2). Oxygenation reactions mediated by cytochrome P450 monooxygenase (P450) play important roles in fungal metabolism of recalcitrant xenobiotic compounds (3)(4)(5)(6)(7)(8)(9). Phanerochaete chrysosporium is a white-rot fungus whose ligninolytic and xenobiotic metabolism has been extensively studied (1)(2)(3)(4)(5)(6)(7)(8)(9).…”

“…Oxygenation reactions mediated by cytochrome P450 monooxygenase (P450) play important roles in fungal metabolism of recalcitrant xenobiotic compounds (3)(4)(5)(6)(7)(8)(9). Phanerochaete chrysosporium is a white-rot fungus whose ligninolytic and xenobiotic metabolism has been extensively studied (1)(2)(3)(4)(5)(6)(7)(8)(9). The sequence of the P. chrysosporium genome revealed the genetic diversity of fungal P450: as many as 154 P450 genes were identified therein (10)(11)(12)(13)(14)(15).…”