Biological delignification of plant components by the white rot fungi Ceriporiopsis subvermispora and Cyathus stercoreus

Lignocelluloses from diverse plant types were treated with the white rot fungi Ceriporiopsis subvermispora (strains CZ-3-8497 and FP-90031-sp) and Cyathus stercoreus. Sources of lignocellulose included: the warm-season grasses sorghum (leaf blades, sheaths, and stems), pearl millet, napiergrass, and maize (stems); the cool-season grass wheat (leaf blades, sheaths, and stems); the legumes alfalfa (stems) and lespedeza (leaflets and stems). Fungus-treated residues were compared with untreated, control samples and with plants treated with a non-delignifying isolate of Trichoderma, Residues were evaluated for improved biodegradability by ruminal microorganisms and modifications in cell wall chemistry by nuclear magnetic resonance, gas chromatography, and ultraviolet absorption microspectrophotometry. Specific plant-fungus interactions were identified that resulted in selective removal of lignin and improved biodegradability by white rot fungi but not the Trichoderma sp. All white rot fungi removed ester-linked p-coumaric and ferulic acids from grass stems, and this phenomenon appeared to account for the significant reduction in aromatic components and improved biodegradability of fungus-treated grass lignocellulose. Cell walls in alfalfa stems were more resistant to biological delignification than those in grasses, with only C. stercoreus removing significant amounts of aromatics and improving biodegradability. All white rot fungi improved the biodegradability of tannin-rich lespedeza samples.