BIOLOGICAL BLEACHING OF WATER-SOLUBLE COAL MACROMOLECULES BY A BASIDIOMYCETE STRAIN

There is need for new effective technologies to convert coal into envi ronmentally acceptable liquid fuels. Thermochemical coal-conversion pr ocesses occur under extreme conditions. Thus there is a potential to u se the biotransformation of coal as a cheap alternative method. A basi diomycete strain, which decomposes coal macromolecules, was isolated f rom humic-acid-rich soil of a lignite surface-mining region. The isola te showed the ability to decolorize liquid dark-brown media containing water-soluble coal-derived substances (humic acids). The presence of an easily available substrate is necessary for the biodegradation. The influence of different culture conditions on the bleaching effect was studied. Evidence for decomposition of water-soluble coal substances was provided by measuring the decrease of absorbance and the modificat ion in the distribution of molecular masses. The degradation process r esulted in a complete decolorization of the coal-derived humic acids a nd was also combined with massive alterations in their molecular struc ture. Solid-state 13C-NMR spectroscopy showed an increase of carboxyli c groups as well as hydroxylated and methoxylated aliphatic groups, wh ich indicates an oxidative attack. Enzymatic analysis showed the prese nce of a Mn peroxidase in the culture supernatant. Extracellular ligni n peroxidase and laccase activities were not detectable. The productio n of the peroxidase was induced by addition of humic acids. But, in vi tro, this enzyme did not cause a decolorization or reduction in molecu lar mass of the coal-derived humic acids.