Extraction, fractionation, and characterization of structural polysaccharides from wheat straw

Wheat straw polysaccharides were fractionated into water soluble, pectic, 80% ethanol soluble, sodium chlorite soluble, hemicellulosic, and cellulose fractions using essentially gravimetric methods. The hemicellulosic material was further separated into a dimethyl sulfoxide soluble fraction and hemicellulose types A-C. The sugar and uronic acid compositions of each fraction were determined by gas chromatography after hydrolysis and conversion to trimethylsilyl ether derivatives and by a spectrophotometric method. The average molecular weights (Mw) of hemicellulosic fractions were estimated using gel permeation chromatography. The major polysaccharides in wheat straw were found to be cellulose (37.19-38.55%), followed by hemicellulosic fractions (30.28-35.01%) and small amounts of water soluble, pectic, 80% ethanol soluble, and sodium chlorite soluble materials. Xylose was found to be the major sugar in all of the hemicellulosic fractions with arabinose, glucose, and galactose as minor constituents. From hemicellulosic fractions A to C, the relative amount of xylose decreased, while the contents of arabinose, glucose, and galactose increased. The contents of phenolic acids and aldehydes remaining in wheat straw hemicellulosic fractions A and B and in cellulose were 0.72, 0.85, and 0.19% respectively