PURIFICATION AND COMPOSITION OF A POLYURONIDE HEMICELLULOSE ISOLATED FROM WHEAT STRAW

Abstract

A homogeneous polyuronide hemicellulose was prepd. from a crude hemicellulose isolated from wheat straw holocellulose by hot water. The method of prepn. consisted of fractional precipitation of the acetylated hemicellulose from chloroform soln. by petroleum ether. Approx. 50% of the recovered fractions consisted of a polysaccharide made up of 28 moles of D-xylose, 5 moles of L-arabinose, and 3 moles of uronic acid and having an [a]20b= -92[degree] and a molar ratio, methoxyl: uronic anhydride, of approx. 1. Intrinsic viscosity measurements indicated a degree of polymerization of approx. 30. Separation of hexosans present in the original hemicellulose showed that they were not chemically combined with the main pentosan fraction. They were recovered admixed with short chain pentosan material containing a higher proportion of arabinose to xylose than the main homogeneous fraction.