Production of manganese peroxidase and organic acids and mineralization of {sup 14}C-labelled lignin ({sup 14}C-DHP) during solid-state fermentation of wheat straw with the white rot fungus Nematoloma frowardii
- Friedrich Schiller Univ., Jena (Germany). Inst. of Microbiology
- Univ. of Helsinki (Finland). Dept. of Applied Chemistry and Microbiology
The basidiomycetous fungus Nematoloma frowardii produced manganese peroxidase (MnP) as the predominant ligninolytic enzyme during solid-state fermentation (SSF) of wheat straw. The purified enzyme had a molecular mass of 50 kDa and an isoelectric point of 3.2. In addition to MnP, low levels of laccase and lignin peroxidase were detected. Synthetic {sup 14}C-ring-labelled lignin ({sup 14}C-DHP) was efficiently degraded during SSF. Approximately 75% of the initial radioactivity was released as {sup 14}CO{sub 2}, while only 6% was associated with the residual straw material, including the well-developed fungal biomass. On the basis of this finding the authors concluded that at least partial extracellular mineralization of lignin may have occurred. This conclusion was supported by the fact that they detected high levels of organic acids in the fermented straw, which rendered MnP effective and therefore made partial direct mineralization of lignin possible. Experiments performed in a cell-free system, which simulated the conditions in the straw cultures, revealed that MnP in fact converted part of the {sup 14}C-DHP to {sup 14}CO{sub 2} and {sup 14}C-labelled water-soluble products in the presence of natural levels of organic acids.
- OSTI ID:
- 346827
- Journal Information:
- Applied and Environmental Microbiology, Vol. 65, Issue 5; Other Information: PBD: May 1999
- Country of Publication:
- United States
- Language:
- English
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