CHARACTERIZATION OF THE ADSORPTION OF XYLOGLUCAN TO CELLULOSE

The binding of xyloglucan- and cello-oligosaccharides to celluloses can be expressed by Langmuir adsorption isotherms, in which the levels of adsorption maxima are all similar but very low. In the present study, although the adsorption constant increased with increases in the degree of polymerization (DP) of the 1,4-beta-glucosyl residues of xyloglucan- and cello-oligosaccharides, the adsorption constant of cellopentitol to cellulose was similar to that of hendecosanosaccharide (glucose/xylose, 12 : 9), demonstrating less extensive binding in the case of xyloglucan oligosaccharides in spite of longer chains of 1,4-beta-glucosyl residues. The binding to cellulose of xyloglucans from pea and Tamarindus indica can also be expressed as Langmuir adsorption isotherms. The adsorption constant for pea xyloglucan with a DP for 1,4-beta-glucosyl residues of 150 was obviously higher than that for Tamarindus xyloglucan with a DP of 3,000. The adsorption maximum and adsorption constant of Tamarindus xyloglucan decreased gradually as the DP of 1,4-beta-glucosyl residues decreased from 3,000 to 64. This result demonstrates that fucosylated pea xyloglucan has a higher adsorption constant for cellulose than non-fucosylated Tamarindus xyloglucan when the DP of 1,4-beta-glucosyl residues is identical. These findings indicate that xyloglucan binds to cellulose as a mono-layer and fucosyl residues contribute to the increase in adsorption affinity.