STRUCTURAL AND SOLUTION PROPERTIES OF CORN COB HETEROXYLANS

The main structural features of the L-arabino-(4-O-methyl-D-glucurono)-D-xylan (AGX) from com cobs were evaluated by means of methylation analysis and C-13-NMR spectroscopy. The heteroxylan consisted of water-soluble and water-insoluble xylan molecules differing in the amount and proportion of non-regularly distributed side chains. Single alpha-(1 --> 2)-linked 4-O-methyl-D-glucopyranosyl uronic acid units and alpha-(1 --> 3)-linked L-arabinofuranose residues, as well as 2-O-beta-D-xylopyranosyl-alpha-L-arabinofuranose moieties constituted the side chains. GPC analysis of the water-soluble fractions coupled with viscometry and light-scattering was used to characterise the molecular weight distribution (MWD) and to establish the Mark-Houwink relationship. The flow properties of aqueous dispersions of the water-soluble and water-insoluble fractions were discussed in relation to their structural properties.