Extraction and characterization of xylose-rich pectic polysaccharide from wheat straw

Xylose-rich pectic polysaccharide (XRPP) was extracted from defatted and protein-free wheat straw with a pH 1.6 solution adjusted with 20% hydrochloric acid. The yield of XRPP was 1.1% of the dried wheat straw. The isolated XRPP contained 44.8% galacturonic acid released by pectolyase treatment and 32.1% released by 2 N trifluoroacetic acid hydrolysis. The XRPP also contained 17.1% neutral sugars released by pectinase treatment and 28.4% released by acid hydrolysis. The major sugar components were found to be xylose and galactose. The weight-average molecular weight (M-w) of XRPP was about 8000 g/mol. The XRPP had low viscosity and low optical rotation as compared to citrus pectin. A comparison of the FT-IR spectroscopic data of citrus pectin and XRPP showed that the extracted XRPP belongs to pectic substances and differs from hemicelluloses with an intensive absorption band at 1740 cm(-1) The content of phenolic acid and aldehydes associated in the isolated XRPP, determined by alkaline nitrobenzene oxidation, was 1.10%.