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

• Published in: Journal of biotechnology 1997-03, Vol.53 (2), p.265-272
• Main Authors: Enoki, Akio, Itakura, Shuji, Tanaka, Hiromi
• Format: Article
• Language: English
• Subjects: Brown-rot fungi; Hydroxyl radical; Soft-rot fungi; White-rot fungi; Wood decay
• ISSN: 0168-1656; 1873-4863
• DOI: 10.1016/S0168-1656(97)01682-9

Extracelluar substances that had single-electron oxidation activity were isolated from cultures of brown-rot and white-rot. The molecular weights of the substances estimated by gel-filtration were very small, in a range of 1000–5000. The substances catalyzed a redox reaction between electron donors and O 2 to produce H 2O 2 via O 2 − and reduced H 2O 2 to HO·. Furthermore, the substances reduced Fe(III) to Fe(II) and strongly adsorbed Fe(II). The production of HO· in cultures of brown-rot 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 substance in Tyromyces palustris cultures. The extent of one-electron oxidation activity of the low molecular weight substance from white-rot basidiomycetes was also correlated with that of the wood-degrading activity, but the phenol oxidase activity was not.