Characterization of lignin-carbohydrate complexes from spruce sulfite pulp

Abstract

Abstract Lignin-carbohydrate complexes (LCCs) were isolated from unbleached acid sulfite pulp by selective enzymatic hydrolysis followed by fiber swelling and extraction. Approximately 80% of the lignin in the pulp was found to be chemically linked to carbohydrates in three major fractions, viz. as one glucan-lignin complex (with 8% lignin) and two hemicellulose-lignin complexes (with 72% lignin). The latter two were further separated into one glucomannan-lignin complex (with ∼25% lignin) and one xylan-lignin-glucomannan complex (with 45–50% lignin). Based on model experiments, it can be concluded that the lignin and carbohydrate moieties are probably linked together through benzyl ether linkages. Xylan is more stable towards acidic hydrolysis than galactoglucomannan, and this finding may explain the greater amount of xylan-rich LCC in the pulp.