Gelation of periodate oxidised scleroglucan (scleraldehyde)

Polysaccharides such as scleroglucan and schizophyllan contain periodate-resistant beta -1,3-linked D-glucan backbones with regularly distributed side chains consisting primarily of single beta -1,6-linked D-glucose residues that are susceptible to periodate oxidation. Side chain oxidation results in the formation of dialdehyde groups and the production of formic acid. During the initial periodate oxidation an increase in the storage modulus (G ') associated with the formation of gels, was observed when the reduced concentration, C-p [eta] was above 3. These gels appeared to be physically stable, whereas aldehyde reduction (e.g. with NaBH4) or oxidation to carboxyl (e.g. with NaClO2 in acetic acid) dissolved the gels. The mechanism of cross-linking can be explained by the formation of intermolecular hemiacetal linkages. The gels were further characterised rheologically in terms of the initial increase in the storage modulus and the stability when stored in seawater at 55 and 90 degreesC, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.