THE INVOLVEMENT OF EXTRACELLUAR SUBSTANCES FOR REDUCING MOLECULAR-OXYGEN TO HYDROXYL RADICAL AND FERRIC IRON TO FERROUS IRON IN WOOD DEGRADATION BY WOOD DECAY FUNGI

Extracelluar substances that had single-electron oxidation activity we re isolated from cultures of brown-rot and white-rot. The molecular we ights of the substances estimated by gel-filtration were very small, i n a range of 1000-5000. The substances catalyzed a redox reaction betw een electron donors and O-2 to produce H2O2 via O-2(-) and reduced H2O 2 to HO .. Furthermore, the substances reduced Fe(III) to Fe(II) and s trongly adsorbed Fe(II). The production of HO . in cultures of brown-r ot fungi was directly proportional to the rates in the degradation of wood, crystalline cellulose and lignin-related model compounds in the cultures. Most of the HO . was produced by a redox reaction between O- 2 and certain electron donors catalyzed by the low molecular weight su bstance in Tyromyces palustris cultures. The extent of one-electron ox idation activity of the low molecular weight substance from white-rot basidiomycetes was also correlated with that of the wood-degrading act ivity, but the phenol oxidase activity was not. (C) 1997 Elsevier Scie nce B.V.