USE OF LIQUID AMMONIA IN THE FRACTIONATION OF WHEAT STRAW HOLOCELLULOSE

Abstract

Wheat straw holocellulose, after soaking in liquid ammonia for 36 hr. at room temperature, was fractionated by successive extractions with cold water, 0.5% sodium carbonate, 0.5% potassium hydroxide, and 2.2% potassium hydroxide. Pretreatment with liquid ammonia increased the material soluble in cold water from 3% to 20.2%. Hemicellulose fractions were precipitated from the extracts by ethanol. A complete analytical balance was obtained by estimating ash, pentosan, uronic acid anhydride, acetyl, and methoxyl contents of the original holocellulose, of each of the fractions and of the residue. Analyses of the isolated fractions showed some systematic differences, with pentosan contents increasing and uronic acid anhydride decreasing progressively in the alkali soluble fractions. D-xylose, L-arabinose, D-glucose, D-galactose, and hexuronic acid in approximate molar ratios of 40:7:2:1:4 were found in the hemicellulose fractions. The presence of the sugars was confirmed by isolation of crystalline derivatives. A uronic acid complex, resistant to hydrolysis, was isolated and the components shown to be D-xylose and a monomethoxyl galacturonic acid.