Composting is nowadays a general treatment method for municipal solid waste. Compostable household waste contains, together with vegetable material, varying amounts of papers and boards. In the European Union composting is regarded as one recycling method for packages and this will probably favour compostable packages, like papers and boards, in the future. Paper is made up of lignocellulose and it may contain up to 20% of lignin. Ecient degradation of papers in composting plants means that biodegradation of lignin is also needed. However, very little is known about lignin degradation by mixed microbial compost populations, although lignin degradation by white-rot fungi has been extensively studied in recent years. Organic material is converted to carbon dioxide, humus, and heat by compost microorganisms. It is assumed that humus is formed mainly from lignin. Thus, lignin is not totally mineralized during composting. The elevated temperatures found during the thermophilic phase are essential for rapid degradation of lignocellulose. Complex organic compounds like lignin are mainly degraded by thermophilic microfungi and actinomycetes. The optimum temperature for thermophilic fungi is 40±50°C which is also the optimum temperature for lignin degradation in compost. Ó

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SUMMARY Basidiomycete fungi subsist on various types of plant material in diverse environments, from living and dead trees and forest litter to crops and grasses and to decaying plant matter in soils. Due to the variation in their natural carbon sources, basidiomycetes have highly varied plant-polysaccharide-degrading capabilities. This topic is not as well studied for basidiomycetes as for ascomycete fungi, which are the main sources of knowledge on fungal plant polysaccharide degradation. Research on plant-biomass-decaying fungi has focused on isolating enzymes for current and future applications, such as for the production of fuels, the food industry, and waste treatment. More recently, genomic studies of basidiomycete fungi have provided a profound view of the plant-biomass-degrading potential of wood-rotting, litter-decomposing, plant-pathogenic, and ectomycorrhizal (ECM) basidiomycetes. This review summarizes the current knowledge on plant polysaccharide depolymerization by basidiomycete species from diverse habitats. In addition, these data are compared to those for the most broadly studied ascomycete genus, Aspergillus , to provide insight into specific features of basidiomycetes with respect to plant polysaccharide degradation.

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White‐rot fungi produce extracellular lignin‐modifying enzymes, the best characterized of which are laccase (EC 1.10.3.2), lignin peroxidases (EC 1.11.1.7) and manganese peroxidases (EC 1.11.1.7). Lignin biodegradation studies have been carried out mostly using the white‐rot fungus Phanerochaete chrysosporium which produces multiple isoenzymes of lignin peroxidase and manganese peroxidase but does not produce laccase. Many other white‐rot fungi produce laccase in addition to lignin and manganese peroxidases and in varying combinations. Based on the enzyme production patterns of an array of white‐rot fungi, three categories of fungi are suggested: (i) lignin‐manganese peroxidase group (e.g.P. chrysosporium and Phlebia radiata), (ii) manganese peroxidase‐laccase group (e.g. Dichomitus squalens and Rigidoporus lignosus), and (iii) lignin peroxidase‐laccase group (e.g. Phlebia ochraceofulva and Junghuhnia separabilima). The most efficient lignin degraders, estimated by 14CO2 evolution from 14C‐[Ring]‐labelled synthetic lignin (DHP), belong to the first group, whereas many of the most selective lignin‐degrading fungi belong to the second, although only moderate to good [14C]DHP mineralization is obtained using fungi from this group. The lignin peroxidase‐laccase fungi only poorly degrade [14C]DHP.

Introduction Historical Outline Bacteria and Microfungi Actinomycetes Other Bacteria Soft‐Rot Fungi and Other Microfungi Brown‐Rot Basidiomycetes White‐Rot Basidiomycetes Mineralization of 14 C‐Labeled Lignins Ligninolytic Enzymes Catabolism of Primary Degradation Products Outlook and Perspectives Patents

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