| Abstract
| - Defatted untoasted soybean cotyledons and hulls were fractionated as water solutes (WSc and WSh)and water unextractable (WUc and WUh). Further fractionation of WUc through deproteinization yieldedthe isolation of a water unextractable solid (WUS) fraction that was mainly composed (molar percent)of galactose (28.1%), glucose (27.8%), arabinose (13.3%), and uronic acids (17.6%), which accountedfor 76% of the water insoluble polysaccharides in soybean cotyledons (WUc). The cell wall (WUS)was sequentially fractionated with chelating agents (chelating agent soluble solids, ChSS) and agradient of agents (dilute alkali, DASS; 1 M alkali, 1MASS; and 4M alkali, 4MASS), which gave afinal cellulosic residue. The ChSS and DASS extracts were characterized as pectin-rich fractions,whereas 1MASS and 4MASS were hemicellulose- and cellulose-rich fractions. Incubation in vitro ofthe WUc fraction with pectinase, cellulase, and xylanase resulted in the release of low amounts (notmore than 5% bound basis) of monosaccharides, mostly uronic acids, xylose, and arabinose. Proteinextraction hardly increased this release after enzymatic incubation (<7%). However, progressivefractionation of the cell wall matrix markedly increased the release of monosaccharides from pectin-(ChSS and DASS) and hemicellulose-rich fractions (1MASS and 4MASS). Significant degradation ofcellulose (up to 20%) was achieved only after complete protein, pectin, and hemicellulose extraction. Keywords: Soybean meal; cell wall components; polysaccharides; enzymes
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