Decay lignin

Thus, most of the degradative reactions of polymeric lignins suggested previously by the analysis of decayed lignin isolated from decayed wood by white-rot fungi were catalyzed by lignin peroxidase. 

A final are we should discuss is color removal. This is perhaps the most difficult impurity to remove from waters. In surface waters color is associated with dissolved or colloidal suspensions of decayed vegetation and other colloidal suspensions. The composition of this material is largely tannins and lignins, the components that hold together the cellulose cells in vegetation. In addition to their undesirable appearance in drinking water, these organics can cause serious problems in downstream water purification processes. For examples ... 

As stated previously, only about 3 % of the lignin content of sound wood was isolated by alcoholic extraction. It was therefore of interest to determine, whether increased amounts of lignin could be extracted from the decayed wood. Thus, both sound and decayed white Scots... 

Table 3. Yields of Lignin Isolated from Sound and Decayed White Scots Pine (98).

Finally, in order to establish unequivocally the identity of the native and residual lignin of white Scots pine wood, the sound wood was first extracted with ethyl alcohol to remove the native lignin fraction. The extracted wood was then decayed by means of the brown rot fungi,... 

Table 4. Comparison of Lignins Isolated from Sound and from Decayed (Lenlinus lepideus) White Scots Pine (79).

Lignin from Sound Wood Lignin from Decayed Wood... 

Porta vaillantii and Lenzites sepiaria, for a fifteen month period. At the end of this time the decayed samples yielded an alcohol extractable lignin in about 20% yield, which was once again found to be chemically identical with the native lignin. These results are recorded in Table 5-... 

Similar studies were conducted by Kudzin and Nord (64) on the hardwoods oak, birch and maple. The fungus employed to bring about the decay of these wood samples was Daedalea quercina. The results of the periodic analyses of the decayed wood and the chemical compositions of the alcohol extractable lignins are outlined in Tables 6 and 7 respectively. 

The secondary wall is located inside the primary wall and can possess pits and sometimes three distinct layers, Sl5 S2, and S3. The secondary wall can contain 25% lignin, and cellulose is more abundant than in primary walls. Support and resistance to decay are the main functions of the primary wall. 

Lignin comprises about 17-33% of the dry weight of wood. It is a complex aromatic polymer which appears to function both as a strengthening agent in the composite wood structure and also as a component which assists in the resistance of the wood towards attack by micro-organisms and decay. 

Naturally lignins that have been modified by chemical reactions, e.g. condensed or sulfonated by pulping, are far less susceptible to biological decay than natural lignins, because the weak, readily hydrolyzable benzyl aryl ether bonds or the readily oxidisable benzyl alcohols of guaiacyl-glycerol units have been sulfonated or transformed by condensation reactions into strong carbon-carbon bonds. 

Kirh, K. T., and A. Kelman Lignin Degradation ivs Related to the Phenol Oxidases of Selected Wood-Decaying Basidiomycetes. Phyto-pathol. 55, 739-745 (1965). 

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