Fractionation and characterization of lignin-carbohydrate complexes (LCCs) from eucalyptus fibers

The effect of milling time on the structure of lignin was investigated by analyzing the quantity and molecular size distribution of thioacidolysis products obtained from wood and pulp of eucalypt (Eucalyptus globulus). After milling, the ability of three solvent systems was determined to completely dissolve the wood or pulp meal. It was found that a mixture of DMSO and 50% aqueous tetrabutylammonium hydroxide was superior to either dimethylacetamide-LiCl or DMSO-tetrabutylammonium fluoride as solvent. By applying the minimum milling time required for complete dissolution, structurally unaltered wood or pulp could be further separated into lignin-carbohydrate fractions. These were analyzed by thioacidolysis. From eucalypt pulp, two different lignin-carbohydrate fractions were obtained, one glucan- and one xylan-enriched fraction, with the latter having more syringyl units in its lignin moieties. The developed solvent system seems to be universal because spruce and flax fibers and pulps could also be dissolved in it after milling.