The Chemistry of Lignin Degradation by White-Rot Fungi

The best known and clearly very important lignin-degrading microorganisms are wood-degrading fungi causing “white rots”. Lignin may be converted into humus and slowly biodegraded in soil. Unlike cellulose and other carbohydrates, lignin is resistant to degradation by most microorganisms. Consequently, the lignin-degrading system of these fungi is very likely a complex of different enzymes. One approach to elucidating the chemistry of lignin degradation by white-rot fungi is to characterize the partially degraded polymer. This would reflect the microbially induced changes in lignin and point to the kind of catabolic reactions involved. Heavily degraded lignins were isolated from spruce wood decayed by white-rot fungi. Changes in lignin in wood at any given time during decay are limited to only a small portion of the total lignin and the bulk of the lignin remains structurally unchanged. Many degradative reactions of lignin have been employed for the characterization of lignin.