Degradation of toxic aromatic compounds by basidiomycetes and its application to bioremediation

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1. Degradation of toxic aromatic compounds by white-rot fungi and ligninolytic enzymesBisphenol A (BPA), which is a starting material of synthetic polymers and has endocrine- disturbing activity, was degraded by the culture of Pleurotus ostreatus. Manganese peroxidase (MnP) purified from the culture of this fungus also degraded BPA to give metabolites which were thought to be produced by one-electron oxidation mechanism of MnP. 4-Chlororezorcinol was degraded by P. ostreatus and other lignin-degrading fungi. MnP degraded 2,4-dichlorophenol to give quinone with concomitant elimination of chloride ion from the substrate.2. Degradation of dioxins by white-rot basidiomycetesDegradation of dioxins was examined by using the lignin-degrading basidiomycete MZ-340 and its crude enzyme preparation. The enzyme preparation was found to decrease the concentration of dioxins substituted with 2 to 8 chlorines. This phenomenon is thought to be caused by the trapping effect of some protein produced in the culture of this fungus.Thirty-five % of dioxin, which was extracted from the contaminated soil by toluene and adsorbed to glass-beads, was degraded by this fungus. By using silica gel column as an adsorbent, 80 % decrease of adsorbed dioxin as observed. Acid treatment of the polluted soil enhanced the degradation of dioxin by the fungus. Long-term experiment using solid phase culture gave 35 % decrease of added dioxin in 360 days culture at room temperature. Thus, a simple treatment of polluted soil by blending with white-rot fungi is available to the bioremediation of the polluted environment.