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  • Title: Structural characterization of feruloylated arabinoxylans and xylans released from water-unextractable cell walls of rye outer layers upon treatment with lichenase and cellulase.
    Author: Cyran MR.
    Journal: Carbohydr Res; 2010 May 07; 345(7):899-907. PubMed ID: 20226439.
    Abstract:
    Destarched and deproteinated water-unextractable material (WUM) of rye outer layers was sequentially treated with lichenase and cellulase to digest beta-glucans and a part of the cellulose. As a result, the polymeric cell-wall material (CWM) initially associated with these polysaccharides was released into solution (AXL and AXC for lichenase- and cellulase-extractable fractions, respectively). A portion of the material that self-aggregated during extractions was further solubilized with DMSO (XD and XD-P for the fraction left in the solution and that precipitated during dialysis, respectively). Arabinoxylans (AXs) recovered from these fractions were composed of populations with different degrees of substitution with alpha-l-arabinofuranosyl residues (Araf). Their counterparts present in the AXL and AXC fractions exhibited higher (0.60 and 0.75) arabinose-to-xylose ratios (Ara/Xyl) and represented 27% and 32% of the isolated AXs, respectively. The xylans of the XD and XD-P fractions had a very low Ara/Xyl ratio (0.16 and 0.09) and accounted for 23% and 18%, respectively. Based on the results of ammonium sulfate fractionation and sugar analysis, it has been shown that AXL consisted of AX subfractions having Ara/Xyl in a narrow range (0.50-0.66). By contrast, the cellulase-extractable AXs were characterized by the presence of the highly branched subfractions (Ara/Xyl of 1.00) as well. Quite unexpectedly, the higher amounts of ferulic acid (FA) were found in the cell-wall fractions enriched in xylans than in the AX-containing fractions. Furthermore, as demonstrated by (1)H NMR and Fourier transform infrared spectroscopy, xylans were substituted with alpha-d-glucuronopyranosyl residues (GlcpA).
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