Brown rot of wood as a model for studies of lignocellulose humification

Humus substances synthesis was investigated in the course of birch wood decomposition by a brown-rot fungus Piptoporus betulinus . With progressing decomposition of wood by brown rot the proportion of high molecular weight humic acids is gradually increased at the expense of fulvic acids, the amount of which is proportionally lowered. The high molecular weight humus constituents are not accumulated in wood decomposed by a laccase producing white-rot fungi despite the availability of suitable phenolic substrates; the low molecular weight fraction of fulvic acids is permanently higher than the fraction of humic acids. The function of laccase in lignin degradation and in biosynthesis of humic acids is problematic.