title: Degradation of benzo[a]pyrene by the litter-decomposing basidiomycete Stropharia coronilla: role of manganese peroxidase.
abstract: The litter-decomposing basidiomycete Stropharia coronilla, which preferably colonizes grasslands, was found to be capable of metabolizing and mineralizing benzo[a]pyrene (BaP) in liquid culture. Manganese(II) ions (Mn(2+)) supplied at a concentration of 200 micro M stimulated considerably both the conversion and the mineralization of BaP; the fungus metabolized and mineralized about four and twelve times, respectively, more of the BaP in the presence of supplemental Mn(2+) than in the basal medium. This stimulating effect could be attributed to the ligninolytic enzyme manganese peroxidase (MnP), whose activity increased after the addition of Mn(2+). Crude and purified MnP from S. coronilla oxidized BaP efficiently in a cell-free reaction mixture (in vitro), a process which was enhanced by the surfactant Tween 80. Thus, 100 mg of BaP liter(-1) was converted in an in vitro reaction solution containing 1 U of MnP ml(-1) within 24 h. A clear indication was found that BaP-1,6-quinone was formed as a transient metabolite, which disappeared over the further course of the reaction. The treatment of a mixture of 16 different polycyclic aromatic hydrocarbons (PAHs) selected by the U.S. Environmental Protection Agency as model standards for PAH analysis (total concentration, 320 mg liter(-1)) with MnP resulted in concentration decreases of 10 to 100% for the individual compounds, and again the stimulating effect of Tween 80 was observed. Probably due to their lower ionization potentials, poorly bioavailable, high-molecular-mass PAHs such as BaP, benzo(g,h,i)perylene, and indeno(1,2,3-c,d)pyrene were converted to larger extents than low-molecular-mass ones (e.g., phenanthrene and fluoranthene).
authors.affiliation: Division of Microbiology, Department of Applied Chemistry and Microbiology, University of Helsinki, PO Box 56, Biocenter 1, Viikinkaari 9, FIN-00014 Helsinki, Finland. kari.steffen@helsinki.fi
authors.forename: Kari T
authors.initials: KT
authors.lastname: Steffen
authors.forename: Annele
authors.initials: A
authors.lastname: Hatakka
authors.forename: Martin
authors.initials: M
authors.lastname: Hofrichter
mesh_terms: D001487:Basidiomycota / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D001564:Benzo(a)pyrene / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002250:Carbon Radioisotopes / Q000378:metabolism; D003470:Culture Media; D008345:Manganese / Q000378:metabolism; D010544:Peroxidases / Q000378:metabolism; D006109:Poaceae / Q000378:metabolism / Q000382:microbiology; D011084:Polycyclic Aromatic Hydrocarbons / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D003470:Culture Media; D011084:Polycyclic Aromatic Hydrocarbons; D001564:Benzo(a)pyrene; D008345:Manganese; D010544:Peroxidases; C051129:manganese peroxidase