LIGNIN BIODEGRADATION PRODUCTS FROM BIRCH WOOD BY PHANEROCHAETE-CHRYSOSPORIUM .1. FRACTIONATION OF METHANOL-EXTRACTIVE AND CHARACTERIZATION OF ETHER-INSOLUBLE LOW-MOLECULAR-WEIGHT FRACTION

Wood of birch (Betula papyrifera) was decayed by the white-rot fungus Phanerochaete chrysosporium to an average weight loss of about 8%.The decayed wood was extracted successively with petroleum ether, chloroform, methanol and dioxane.The methanol-extractive was separated into high-molecular-weight acidic fraction-1, -2 and -3 (M-HA-1, M-HA-2 and M-HA-3), and low-molecular-weight acidic and phenolic fractions (M-LA and M-LP) by means of solubility in acids, bases and organic solvents. The M-LA fraction was further divided into ether-soluble and ether-insoluble M-LA fractions. The nature of the ether-insoluble fraction was characterized by 13C NMR spectroscopy. The results indicated that the fraction is composed of aliphatic substances, and oligomeric biodegraded lignins and carbohydrates with substructures of the type saccharic acid, probably including oligomeric biodegraded lignin-carbohydrate-complexes.The lignins in the ether-insoluble fraction are guaiacyl-syringyl type lignins containing 4-0-alkylated syringic and vanillic acid substructures in significant quantity. Moreover, the former is predominant over the latter, indicating that syringyl type substructures are more susceptible to oxidative cleavage of Ca-Cß bond than guaiacyl type substructures. In addition to lignins, carbohydrates in birch wood also undergo degradation during the decay of birch wood by Ph. chrysosporium. © 1990, Walter de Gruyter. All rights reserved.