Screening for basidiomycetous fungi capable of degrading 2,7-dichlorodibenzo-p-dioxin.

We devised a screening method to obtain basidiomycetous fungi capable of degrading dioxins. About 200 fungal strains were selected from more than 1500 strains by their ability to decolorize Remazol brilliant blue R dye as an indicator. To attempt to eliminate the factor of dioxin sorption by mycelia, we prepared two series of living cultures exposed either long term or short term to 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD), and compared the decreases in the levels of this chemical. In only 11 strains was there a significant difference between the two treatments. We chose Panellus stypticus strain 99-334 as a new, effective dioxin degrader, because it gave a close to 100% decrease in 2,7-DCDD levels (from an initial concentration of 10 microM) after 40 days of exposure. The detection of a metabolic intermediate (1-chloro-3,4-dihydroxybenzene) by gas chromatography-mass spectrometry analysis supported the ability of this strain to degrade 2,7-DCDD.