Fumihide Yamaguchi

Extraction and purification of pectic polysaccharides from soybean okara and enzymatic analysis of their structures

Pectic polysaccharides (6.74 g) were extracted from soybean okara (soybean curd waste, 30 g) with sodium hexametaphosphate solution. The extract was separated by DEAE-cellulose chromatography into galacturonate poor and galacturonate rich fractions. The fractionated polysaccharides were exhaustively degraded by three kinds of pectinase and two kinds of hemicellulase, namely exo- and endopolygalacturonases, exopolygalacturonate lyase, exogalactanase and exoarabinase. The values of the degradation limit revealed that the soybean pectic polysaccharides comprise regions of galacturonan and rhamnogalacturonan carrying side chains composed mainly of homogeneous arabinan and galactan. The galacturonan regions were distributed at both the reducing and nonreducing ends of the polysaccharide.