Frequency and alkali resistance of lignin-carbohydrate bonds in wood

Abstract

Milled-wood enzyme lignin, the residue obtained by polysaccharidase digestion of vibratory ball-milled wood, which contains nearly all of the lignin-carbohydrate bonds in wood, was used to investigate the nature of these bonds. A lignin-carbohydrate bond frequency of 0.028 per phenyl propane unit was experimentally determined. Mild alkaline treatment cleaved 10 to 20% of the lignin-carbohydrate bonds, and these alkali labile bonds were proposed to be mainly uronic acid ester linkages to lignin. Most of the remaining lignin-carbohydrate bonds in milled wood enzyme lignin were resistant to cleavage under the conditions of soda pulping.