SUCCESSIVE MINERALIZATION AND DETOXIFICATION OF BENZO[A]PYRENE BY THEWHITE-ROT FUNGUS BJERKANDERA SP. STRAIN BOS55 AND INDIGENOUS MICROFLORA

White rot fungi can oxidize high-molecular-weight polycyclic aromatic hydrocarbons (PAM) rapidly to polar metabolites, but only limited mine ralization takes place. The objectives of this study were to determine if the polar metabolites can be readily mineralized by indigenous mic roflora from several inoculum sources, such as activated sludge, fores t soils, and PAM-adapted sediment sludge, and to determine if such met abolites have decreased mutagenicity compared to the mutagenicity of t he parent PAM, C-14-radiolabeled benzo[a]pyrene was subjected to oxida tion by the white rot fungus Bjerkandera sp. strain BOS55, After 15 da ys, up to 8.5% of the [C-14]benzo[a]pyrene was recovered as (CO2)-C-14 in fungal cultures, up to 73% was recovered as water-soluble metaboli tes, and only 4% remained soluble in dibutyl ether, Thin-layer chromat ography analysis revealed that many polar fluorescent metabolites accu mulated, Addition of indigenous microflora to fungal cultures with oxi dized benzo[a]pyrene on day 15 resulted in an initially rapid increase in the level of (CO2)-C-14 recovery to a maximal value of 34% by the end of the experiments (>150 days), and the level of water-soluble lab el decreased to 16% of the initial level. In fungal cultures not inocu lated with microflora, the level of (CO2)-C-14 recovery increased to 1 3.5%, while the level of recovery of water-soluble metabolites remaine d as high as 61%, No large differences in (CO2)-C-14 production were o bserved with several inocula, showing that some polar metabolites of f ungal benzo[a] pyrene oxidation were readily degraded by indigenous mi croorganisms, while other metabolites were not, Of the inocula tested, only PAM-adapted sediment sludge was capable of directly mineralizing intact benzo[a] pyrene, albeit at a lower rate and to a lesser extent than the mineralization observed after combined treatment with white rot fungi and indigenous microflora. Fungal oxidation of benzo[a]pJTen e resulted in rapid and almost complete elimination of its high mutage nic potential, as observed in the Salmonella typhimurium revertant tes t performed with strains TA100 and TA98. Moreover, no direct mutagenic metabolite could be detected during fungal oxidation, The remaining w eak mutagenic activity of fungal cultures containing benzo [a] pyrene metabolites towards strain TA98 was further decreased by subsequent in cubations with indigenous microflora.