Fractional isolation and partial characterization of non-starch polysaccharides and lignin from sago pith

Sago pith non-starch polysaccharides were fractionated into cold water solu bles (2.6%), hot water solubles (0.8%), dimethylsulfoxide solubles (0.8%), 5% NaOH soluble hemicelluloses (1.2%), 24% KOH-2% H3BO3 soluble hemicellulo ses (0.6%), and cellulose (5.3%). Lignin was measured by 5% NaOH extraction (0.6%) and sodium chlorite oxidation (4.2%). Glucose and rhamnose were the major sugars in cold and hot water soluble non-starch polysaccharides. The neutral sugars in dimethylsulfoxide (DMSO) soluble non-starch polysacchari des were found to be enriched in rhamnose, xylose, glucose, and arabinose. Extraction of sage pith with aqueous 5% NaOH produced hemicelluloses, which were enriched in xylose and, to a lesser extent, glucose, arabinose, galac tose, and rhamnose-containing polysaccharides, together with 7.4% uronic ac ids and 3.9% lignin. Further extraction of the delignified pith residue wit h aqueous 24% KOH and 2% H3BO3 removed the residual hemicellulosic fraction , which was enriched in glucose and xylose-containing polysaccharides, toge ther with 5.8% uronic acids and 1.1% associated residual lignin. Six phenol ic acids and aldehydes were detected in the mixtures of alkaline nitrobenze ne oxidation of 5% NaOH soluble lignin and associated lignin in hemicellulo ses and cellulose fractions. The lignin fraction contained a high proportio n of non-condensed syringyl units and small amounts of non-condensed guaiac yl units as well as fewer non-condensed p-hydroxyphenyl units. (C) 1999 Els evier Science B.V. All rights reserved.