Topochemistry of the fungal degradation of lignin in birch wood as related to the distribution of guaiacyl and syringyl lignins

✍ Scribed by T. Kent Kirk; Hou-min Chang; L. F. Lorenz

• Publisher: Springer
• Year: 1975
• Tongue: English
• Weight: 330 KB
• Volume: 9
• Category: Article
• ISSN: 0043-7719
• DOI: 10.1007/bf00353387

✦ Synopsis

Samples of non-decayed birch wood and samples decayed to weight losses of 21, 44, and 67 % by Coriolus versicolor were subjected to acidolysis (4 h reflux in dioxane-water, 9 : 1 by volume, containing 0.2 M HC1). The yields of the two major products, 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-2-propanone (ketol I) and 3-hydroxy-l-(4-hydroxy-3,5-dimethoxyphenyl)-2-propanone (ketol II), as a percentage of residual lignins, decreased prog,essively with increasing decay. Even so, substantial yields of I and II were obtained from the decayed wood, suggesting that during decay a considerable amount of the lignin remaining in the wood was as yet unaltered (e. g. ~ 50% at a 67 % weight loss). This result indicates that lignin is degraded from exposed surfaces; the decreasing yields of I and II with decay show that the surfaces become progressively larger. The more rapid decrease in the yield of ketol II than in the yield of ketol I indicates that syringyl elements were degraded more rapidly than guaiacyl elements. The fungal enzymes, acting progressively from the lumen surfaces toward the middle lametla, encountered syringylrich lignin first.