<Ogirinal>Properties of Enzyme-Unhydrolyzable Residue of Lignin-Carbohydrate Complexes Isolated from Beech Wood

Abstract

Water-soluble lignin-carbohydrate complexes (LCC-W) isolated from beech MWL were treated twice with commercial cellulase (ONOZUKA R-10). The unhydrolyzable fraction precipitated by enzyme treatment was divided into three fractions according to the previous report. All fractions contained neutral sugars and uronic acid. Composition and methylation analysis of sugars remaining in each fraction indicated that xylose, arabinose and galactose residues are linked to lignin possibly by benzyl ether linkage at C-2 or C-3, C-5 and C-6 positions, respectively. The results from alkaline treatment also suggested that these sugars are directly linked to lignin. The existence of alkali-stable linkage between lignin and carbohydrate also was characterized. An analysis of phenolic hydroxy group of lignin moiety suggested that phenol-glycoside linkage is not involved. The results of spectroscopic analysis indicated that lignin moiety in LCC-W consisted of typical hardwood lignin.