Decolorization of coal humic acid by extracellular enzymes produced by white-rot fungi

In order to produce useful materials from coal humic acid by enzymic action, the screening of microorganisms able to decolorize coal humic acid has been carried out. In this study, the enzymic decolorization and depolymerization of coal humic acid by three white-rot fungal strains isolated in our laboratory were investigated. The relation between four kinds of extracellular enzymes-laccase (Lac), arylalcohol oxidase (AAO), lignin peroxidase (LiP) and manganese peroxidase (MnP)-excreted by the white-rot fungi and the decolorization of coal humic acid was examined. The fungus strain FTN gave the highest decolorization rate of coal humic acid (50% on incubation day seven and 73% on day twenty). As MnP showed the highest activity of the four extracellular enzymes in all three fungi, it is considered likely that MnP promotes the decolorization of coal humic acid.