THE FRACTIONAL COMPOSITION OF POLYSACCHARIDES AND LIGNIN IN ALKALINE PRETREATED AND STEAM PRESSURE TREATED WHEAT-STRAW

Wheat straw was firstly pre-treated with 1.5% sodium hydroxide at 20 d egrees for 6 h, then extracted with 0.25% ammonium oxalate for 4 h at 85 degrees, followed by steam pressure treatment at 120 degrees/2 bar for 7 h. The residue was then delignified using acidic sodium chlorite solution, followed by treatment with 24% potassium hydroxide with 2% boric acid for 2 h at 20 degrees, for determination of hemicellulose a nd alpha-cellulose. The yields were determined by thermal analysis and converted to control sample. The data showed that the pre-treatment w ith 1.5% sodium hydroxide significantly influenced the solubility of h emicellulose, while the steam pressure treatment had a pronounced effe ct on the lignin solubility. It was also found that xylose was the maj or sugar constituent in the hemicellulose fraction and the :hydrolysat e of NaOH pre-treatment, whilst glucose and galactose were minor compo nents. The content of arabinose was higher in the hydrolysate obtained from the pre-treatment than that in hemicellulose fraction, whereas x ylose in hemicellulose was higher than that in the hydrolysate of the pre-treatment. The content of uronic acid in the hydrolysate obtained from the 1.5% NaOH I pre-treatment was higher than that in hemicellulo se fraction. The contents of phenolic acids and aldehydes in wheat str aw, pre-treated (1.5% NaOH, 20 degrees, 6 h) wheat straw, hemicellulos e and cellulose extracted from pre-treated and steam pressure treated wheat straw were 6.00, 4.18, 0.092 and 0.11%, respectively. The range of molecular weights both in hemicellulose and in pre-treated straw hy drolysate was also studied.