Stepwise Extraction of Hemicelluloses with Water and Alkali from Larch Wood and their Sugar Compositions
The aim of the present study was to isolate hemicelluloses by stepwise extraction with water and alkali from larch (Larix principis-rupprechtii Mayr) sapwood and heartwood. One water-soluble arabinogalactan (AG) and three alkali-soluble hemicelluloses- arabinoglucuronoxylan (AGX), galactoglucomannan (GGM) and glucomannan (GM) were obtained. The yield of AG extracted with hot-water from larch heartwood was 7.57%, it was 17.96% in total of three alkali-extracted hemicelluloses. There was no significant difference in the yield of hemicelluloses from sapwood and heartwood. Monosaccharide compositions of the hemicelluloses were determined by high performance liquid chromatography after acid hydrolysis. The results showed that galactose and mannose were the main glycosyl units of hemicellulose, followed by xylose. Galactose mainly derived from AG, whereas mannose and xylose originated from alkali-extracted hemicelluloses.