Isolation and structural characterization of lignin-carbohydrate complexes from sisal and abaca fibers

Abstract

Lignin carbohydrate complexes (LCC) were isolated from sisal and abaca. Two LCC fractions, namely GL and XL, were isolated in a quantitative manner. GL fractions were enriched in glucans and depleted in lignin whereas XL fractions were depleted in glucans but were enriched in xylans and lignin. The lignin moieties in the different LCC fractions of sisal and abaca are structurally different from each other, with a lignin that is enriched in S-units, less condensed, that is preferentially associated to xylans, and a lignin with more G-units, more condensed, that is preferentially associated to glucans. In addition, the analyses indicated that the acetate groups attached to the γ-carbon of the lignin side-chains in abaca and sisal were completely hydrolyzed and removed during the isolation procedure.