Structural characterization of feruloylated arabinoxylans and xylans released from water-unextractable cell walls of rye outer layers upon treatment with lichenase and cellulase

• Published in: Carbohydrate research 2010-05, Vol.345 (7), p.899-907
• Main Author: Cyran, Malgorzata R.
• Format: Article
• Language: English
• Subjects: Ammonium Sulfate - chemistry; Arabinoxylans; Bacillus subtilis - enzymology; Cell Wall - chemistry; Cellulase - metabolism; Chemical Fractionation; Chemical Precipitation; Chromatography, Gel; Ferulic acid; Glycoside Hydrolases - metabolism; Lichenase and cellulase digestion; Magnetic Resonance Spectroscopy; Phenols - chemistry; Rye outer layers; Secale - cytology; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Structure; Talaromyces - enzymology; Water - chemistry; Xylans; Xylans - chemistry; Xylans - isolation & purification; Xylans - metabolism
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2010.02.009

Destarched and deproteinated water-unextractable material (WUM) of rye outer layers was sequentially treated with lichenase and cellulase to digest β-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 α- l-arabinofuranosyl residues (Ara f). 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 1H NMR and Fourier transform infrared spectroscopy, xylans were substituted with α- d-glucuronopyranosyl residues (Glc pA).