Corn fiber was chemically modified with ion-exchanging groups to prepare water-soluble polysaccharides. The soluble fractions were dialyzed using dialysis tubing (1 kDa) and the material retained inside the tubing was filtered through 10 kDa membranes to separate into fractions with molar mass of 1-10 kDa and greater than 10 kDa. The yield of solubilized material of molar mass higher than 10 kDa (47%) and 1-10 kDa (17%) obtained by sulfonation in the presence of NaOH under vacuum was greater than the yields of the treatment at the ambient pressure (43% and 2%) and also in experiments run with only KOH (40% and 5%) or NaOH (38% and 5%) at ambient pressure. The sugar analysis indicated that they were typical glucuronogalactoarabinoxylans containing 46-57% d-xylose (Xyl), 25-33% l-arabinose (Ara) and 6-12% d-galactose (Gal).