Oxidation and ring cleavage of dibenzofuran by the filamentous fungus Paecilomyces lilacinus

Abstract

The ability of the imperfect soil fungus Paecilomyces lilacinus to transform the environmental pollutant dibenzofuran was investigated. Transformation of dibenzofuran and related derivatives lead to 14 products, which were identified by UV spectroscopy, mass spectrometry, and proton nuclear magnetic resonance spectroscopy. Biotransformation was initiated by two separate hydroxylation steps, leading to the accumulation of 4-monohydroxylated and 4-dihydroxylateddibenzofurans. Hydroxylation at both aromatic rings produced 2,7-dihydroxydibenzofuran, 3,7-dihydroxydibenzofuran, and 2,8-dihydroxydibenzofuran. Further oxidation yields ring cleavage of dibenzofuran, which has not been described before for filamentous fungi. The ring fission products were identified as benzo[ b]furo[3,2-d]-2-pyrone-6-carboxylic acid and [2-(1-carboxy-methylidene)-benzofuran-3-ylidene]-hydroxy-acetic acid and its derivatives hydroxylated at carbon 7 and 8 at the non-cleaved ring. Other metabolites were riboside-conjugates of 2-hydroxydibenzofuran and 3-hydroxydibenzofuran. The results showed that P. lilacinus transforms the hydrophobic compound dibenzofuran by phase I/phase II reactions to produce hydroxylated products and excretable sugar conjugates.

Conversion of polycyclic aromatic hydrocarbons, methyl naphthalenes and dibenzofuran by two fungal peroxygenases

“…Several mono-and di-hydroxylated metabolites were detected after treatment of Dbf with monoxygenases of the ascomycetous mold Paecilomyces lilacinus (Gesell et al 2004) or with whole-cells of the zygomycete Cunninghamella elegans (Cerniglia et al 1979). The latter fungus has an enzymatic system that is comparable with the microsomal monooxygenase activities found in rat liver (Zhang et al 1996).…”

UV Filters Biodegradation by Fungi, Metabolites Identification and Biological Activity Assessment

“…As a consequence, the enzymes carrying out the transfer would be UDP-glucosyltransferase when the added molecule is glucose [71] and UDP-xylosiltransferase in the case that conjugation occurs with xylose, as it has been previously reported for other xenobiotics in T. versicolor [55]. Conjugation with ribose has been also described for other fungi [56], ant it can also occur in T. versicolor since the molecular weight of the resulting conjugate would be the same than for the xylose-conjugated metabolite. Sugar residues attach to the molecule through an O-glycosidic bond with the hydroxyl groups present in the aromatic ring [55,56].…”

“…Conjugation with ribose has been also described for other fungi [56], ant it can also occur in T. versicolor since the molecular weight of the resulting conjugate would be the same than for the xylose-conjugated metabolite. Sugar residues attach to the molecule through an O-glycosidic bond with the hydroxyl groups present in the aromatic ring [55,56]. In BP3, the conjugation should occur through the unique free hydroxyl of the molecule, whereas BP1 presents two possible alternatives.…”

“…Therefore, those data suggested that the metabolite with m/z 383 might be BP3 conjugated with a molecule of 132 Da. Several studies claim that the formation of conjugated metabolites with pentoses (mainly xylose and ribose) and hexoses (mainly glucose) is a predominant pathway in the degradation of chemicals by white-rot fungi, especially in phenolic hydroxyl groups [55,56]. In this case, the addition of a pentose via glycosidic bond to the BP3 with the consequent loss of one molecule of water corresponds to an increase in the molecule mass of 132 Da.…”

Phase II metabolites of etofesalamide in filamentous fungi1

“…Compared with the phase II reactions in humans, glucoside conjugation is the major metabolic pathway in microorganisms, and it is used extensively to study the detoxification of cytotoxins and carcinogens [12][13][14] . Riboside conjugation is obviously another potential phase II reaction in biotransformation in filamentous fungi, but only one such conjugate has been reported recently [15] . …”