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Depolymerization of low-rank coal by extracellular fungal enzyme systems. I. Screening for low-rank-coal-depolymerizing activities

Hofrichter, M., Fritsche, W.
Applied microbiology and biotechnology 1996 v.46 no.3 pp. 220-225
Basidiomycota, agar, bleaching, chromatography, coal, depolymerization, ecophysiology, enzyme activity, fungi, humic acids, molecular weight, peroxidases, screening
A miniscale screening system was developed to detect depolymerizing activities of fungi toward lowrank coals. This system was suitable for the determination of changes in molecular masses as well as for the measurement of the enzymes responsible. A total of 486 fungal strains of different ecophysiological and taxonomic groups were tested for their ability to decolorize agar media containing coal-derived humic acids; 38 wood- and litter-decaying basidiomycetes caused a strong bleaching effect and 49 a weak effect. In contrast, micromycetes were proved to be unable to decolorize the coal substances. The wood-decaying fungus Nematoloma frowardii b19 most effectively bleached the medium. It could be demonstrated by gel-permeation chromatography that the strain really depolymerizes the high molecular-mass fractions of coal humic acids by forming fulvic-acid-like compounds. Extracellular enzyme activities of oxidases and peroxidases towards 2,2'-azinobis(3-ethylbenzthiazolinesulphonate) were extractable from the agar media.