Biotransformation of the insecticide lindane by the white rot basidiomycete Phanerochaete chrysosporium has been investigated in liquid cultures. Some polar metabolites and carbon dioxide were produced from the pesticide. Among the metabolites identified were tetrachlorocyclohexene, tetrachlorocyclohexene epoxide and tetrachlorocyclohexenol. When used as a substrate, tetrachlorocyclohexene was also converted by the fungus to tetrachlorocyclohexenol, polar metabolites and carbon dioxide. Three incubation conditions leading to low and high peroxidase production were assayed. Data from these experiments, as well as in-vitro incubations with purified enzymes, ruled out any involvement of the peroxidases in lindane biotransformation and mineralization. Moreover, 1-aminobenzotriazole (a P450 inactivator) drastically reduced pesticide metabolism. Conversely, phenobarbital (a P450 inducer) did not significantly increase lindane breakdown.
Biotransformation of atrazine by the white rot fungus Phanerochaete chrysosporium was demonstrated by a 48% decrease of the initial herbicide concentration in the growth medium within the first 4 days of incubation, which corresponded to the mycelium-growing phase. Results clearly established the mineralization of the ethyl group of the herbicide. Analysis of the growth medium showed the formation of hydroxylated and/or N-dealkylated metabolites of atrazine during fungal degradation.
: The ability of the white rot basidiomycete Phanerochaete chrysosporium to transform s-triazine herbicides has been investigated in laboratory experiments. The chlorinated metabolites formed during atrazine Ndealkylations were not further transformed by the fungus, whereas hydroxyatrazine was converted to an unknown product. P. chrysosporium was also able to carry out the N-dealkylation of the herbicides simazine, propazine and terbuthylazine. Herbicide metabolism was not supported by puriÐed peroxidases. The highest rates of herbicide N-dealkylation were obtained in liquid cultures maintained under moderate temperature allowing a long mycelium growing phase. Atrazine transformation was found to be supported by the mycelium, which contained signiÐcant amounts of microsomal cytochrome P450. Herbicide N-dealkylation was decreased in the presence of 1-aminobenzotriazole, in agreement with the involvement of P450 monooxygenases in atrazine metabolism.
The transformation of pentachlorophenol (PCP) by Phanerochaete chrysosporium 1-1512 in relation to pentachloroanisole (PCA) was studied in two different modes of culture. The degradation of PCP by immobilized cells in agitated medium was compared with that by static cultures. Results clearly established the advantage of an immobilized culture for mineralization of PCP: 23% of C 0 2 released for fungus immobilized on stainless steel mesh rings as compared with 11 % for static cultures. PCA, a metabolite of PCP, was formed only in static cultures and underwent a limited mineralization. Moreover, experiments performed with mycelium and culture supernatant (in the presence of cycloheximide) clearly demonstrated that PCA formation was catalyzed by the biomass in static cultures of P. chrysosporium. Assays in vitro did not establish any involvement of lignin or manganese peroxidases in PCP or PCA transformation.Resum6 : La degradation du pentachlorophCno1 (PCP) par Phanerochaete chrysosporium 1-1512 et la formation de pentachloroanisol (PCA) ont Ct C CtudiCes selon deux modes de cultures diffkrents. La dtgradation du PCP avec des cellules immobilisCes dans un milieu agitC est comparCe i des conditions statiques. Les rCsultats mettent en Cvidence l'avantage des cellules immobilisCes pour la minCralisation du PCP : 23% de CO, piCgC avec le champignon immobilisC sur des anneaux de grille metallique et 11 % seulement avec les cultures statiques. Le PCA, un mCtabolite du PCP, est produit uniquement dans les cultures statiques et ne subit qu'une faible minCralisation. De plus des essais rCalisCs avec du mycClium ou du surnageant de culture (en prCsence de cycloheximide) montrent clairement que la biomasse est i l'origine de la formation de PCA dans les cultures statiques. Des essais rCalisCs in vitro n'ont pas permis d'impliquer directement les lignine et manganese peroxydases dans la transformation du PCP ou du PCA.
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