The biotransformation of benzo [a]pyrene by purified extracellular laccase of Pycnoporus cinnabarinus was investigated in bench scale reactors. The reaction required the presence of exogenous mediator ABTS. Most of 95% of the substrate was converted within 24 hours. The enzyme preparation oxidised the substrate mainly to benzo[a]pyrene 1,6-3,6-and 6,12-quinones in a 2/1/1 ratio after 24 hours incubations.

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.

We studied the fate of 14 C-labelled phthalic acid and benzo[a]pyrene applied to the soil by the way of contaminated sewage sludge in model ecosystems allowing the simultaneous assessment of physicochemical and biological descriptors. Here we show that the mineralisation of phthalic acid is higher than 30% after 90 days in the situation of direct soil contamination, amendment with contaminated digested or composted sludge. It is reduced to 10% in the presence of the raw sludge. In that case, the values of phospholipidic fatty acids and dehydrogenase activity are the highest. By contrast, benzo[a]pyrene is recalcitrant to biodegradation whatever the type of soil contamination. We show also that the chemicals present in the sludge are poorly transferred to soil leachates and plant seedlings.

The biotransformation of 16 polycyclic aromatic hydrocarbons (PAHs) in mixture was investigated in reactors in the presence of purified laccases of the fungus Pycnoporus cinnabarinus, ABTS as a redox mediator, 25% acetonitrile, and Tween 20. Several hydrocarbons from a synthetic mixture, such as anthracene and benzo[a]pyrene, were converted up to 80% into quinones, whereas others also belonging to three-and five-ring chemicals were less transformed. Chrysene and benzo[k]fluoranthene were not oxidized by the laccase mediator system. Moreover, hydrocarbons extracted from an industrial soil were all recalcitrant to enzymatic attack. This lack of reactivity of the laccases toward the hydrocarbons could be due to the

Five strains of T. versicolor were cultured on wet sand in the presence of phenanthrene and benzo[a]pyrene. Biodegradation studies and metabolite determination were performed. Microcosms containing industrial soil polluted by PAHs and supplemented with organic carriers overgrown with the fungi were then evaluated for fungal growth, laccase production and pollutant degradation.