Structural characterization of feruloylated arabinoxylans and xylans released from water-unextractable cell walls of rye outer layers upon treatment with lichenase and cellulase.
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).
Cyran
Malgorzata R
MR
Laboratory of Nutritional Evaluation of Plant Materials, Institute of Plant Breeding and Acclimatization, Radzikow, 05-870 Blonie, Poland.
D000645:Ammonium Sulfate / Q000737:chemistry; D001412:Bacillus subtilis / Q000201:enzymology; D002473:Cell Wall / Q000737:chemistry*; D002480:Cellulase / Q000378:metabolism*; D005591:Chemical Fractionation; D011232:Chemical Precipitation; D002850:Chromatography, Gel; D006026:Glycoside Hydrolases / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010636:Phenols / Q000737:chemistry; D012434:Secale / Q000166:cytology*; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D032901:Talaromyces / Q000201:enzymology; D014867:Water / Q000737:chemistry*; D014990:Xylans / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
D010636:Phenols; D014990:Xylans; D014867:Water; D006026:Glycoside Hydrolases; D002480:Cellulase; C028020:licheninase; D000645:Ammonium Sulfate