Exploration into the structural characteristics and functional properties of exopolysaccharide synthesized by...

Microbial exopolysaccharides have attracted considerable interest for their diverse applications in biomedical industry, food processing, and environmental remediation. However, exopolysaccharides with high molecular weight and strong gel properties are relatively rare. In this study, an exopolysaccharide with high molecular weight was isolated from the fermentation broth of Pseudoduganella armeniaca ZMN-3 and purified using DEAE-52 ion-exchange and Sephadex G-75 chromatography. The yield of crude exopolysaccharide reached 2.72 ± 0.32 g/L. DSPS-2 consisted mainly of 45.6% glucose, 24.7% rhamnose, 17.6% galactose, 10.6% glucosamine, and a small amount of guluronic acid, with an average molecular weight of 3.65 × 10⁵ Da. Structural analysis, such as GC-MS, SEM, TEM, and AFM revealed multiple glycosidic linkages forming a heteropolysaccharide with a fibrous and porous morphology. In terms of the functional properties, the results of FTIR and XPS confirmed the presence of hydroxyl, amino, and carboxyl groups in DSPS-2. DSPS-2 exhibited greater thermal stability with a degradation temperature about 275 °C. Rheological measurements confirmed pseudoplastic shear-thinning behavior of DSPS-2, and it exhibited strong gelation in the presence of Cr³⁺. These results demonstrated that DSPS-2 possessed favorable structural stability, viscosity, and metal-responsive gelation, highlighting its coordination with metal cations and providing a theoretical foundation for its potential application in environmental remediation.