BIODEGRADATION MECHANISM OF LIGNIN BY WHITE-ROT BASIDIOMYCETES

White-rot basidiomycetes such as Coriolus versicolor, Phanerochaete ch rysosporium and Phlebia radiata have been found as typical lignin degr ader. During the past 15 years chemistry and biochemistry of lignin bi odegradation by white-rot basidiomycetes have considerably advanced by means of chemical analysis of the biodegraded lignin and studies of t he degradation mechanism of lignin substructure model compounds by lig ninolytic cultures of these basidiomycetes and their enzymes. Excellen t reviews (Kirk and Farrell, 1987; Schoemaker, 1990; Umezawa and Higuc hi, 1991) concerning microbial and enzymatic degradation of lignin hav e recently appeared. We (Higuchi and Nakatsubo, 1980; Higuchi, 1990) s ynthesized major lignin substructure model compounds linked by beta-O- 4, beta-5, beta-1, beta-beta' and 5-5' bonds and used as substrates fo r cultures of P. chrysosporium and C. versicolor and their enzymes, li gnin peroxidase and laccase. The degradation products were extracted w ith ethyl acetate and identified by NMR and GC-MS to elucidate degrada tion pathways of the lignin substructure model compounds. The results are classified to the cleavage of side chain and aromatic ring opening of the compounds.