A new bacterial exopolysaccharide (YAS34). II. Influence of thermal treatments on the conformation and structure. Relation with gelation ability

This paper describes an original mechanism of evolution of a polysaccharide system occurring during thermal treatments. Under its native conformation, the YAS34 polymer presents a solution character in the dilute and semi-dil ute regimes. However, the zero shear rate viscosity indicates existence of interchain interactions which disappear on the deacetylated polymer. Therma l treatments over the temperature of conformational change produce a progre ssive and irreversible evolution of the physical properties when the polyme r is under its sodium salt form. This evolution was related to a modificati on of the arrangement of acetyl substituents. The heated polysaccharide giv es thermoreversible gel which is very elastic. A gelation mechanism is prop osed based on formation of helical segments connecting the network. (C) 200 0 Elsevier Science B.V. AU rights reserved.