Organisms Degrading Lignin

Lignin is an amorphous, highly aromatic heterogenous, 3-D branched polymer (Buswell and Odier 1987; Higuchi 1985) with its substituents connected by carbon-carbon and ether linkages. There are different lignin structures consisting of various amounts of the three cinnamyl alcohol precursors present: p-coumaryl, coniferyl, and synapyl alcohols. These alcohols give rise to p-hydroxyphenyl units, guaiacyl units, and syringyl units, respectively, in lignin (Higuchi 1985; Kirk and Farrell 1987). The lignin cinnamyl alcohol precursors produce phenoxy radicals which randomly couple.

White-rot is characterized by the bleached white color of advanced wood decay due to fungi (white-rot fungi) and other organisms. White-rot can totally degrade all major wood polymers, including lignin (Crawford and Crawford 1980; Kirk 1971). Lignin is significantly de-aromatized. The degradation follows two general patterns (a) simultaneous attack on lignin and polysaccharides or (b) preferential or selective removal of lignin and/or hemicellulose without extensive depletion of cellulose (Buswell 1991). White-rot fungi degrading lignin in preference to polysaccharides are Pycnoporus cinnabarinus, Pleurotus ostreatus, Phlebia radiata, and Phlebia (Merulius) tremellosus (Ander and Eriksson 1977).

Other organisms degrading lignin include the brown-rot fungi, the soft-rot fungi, which seem capable of some demethylation and possibly degradation of side chains and aromatic rings (Ander and Eriksson 1978; Buswell 1991) and some bacteria associated with the Actinomycetes and Eubacteria (Kirk 1971). Bacteria may extensively degrade, demethoxylate, and modify aromatic rings and side chains.

Making Your Own Wine

Making Your Own Wine

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