Study on the structural characterization of Premna microphylla Turcz polysaccharides and their improvement effect on the properties of chitosan composite gel

Bioactive polysaccharide composite gels provide strategy for improving the defects of chitosan (CS) gel. The aim of this study was to characterize the structure of Premna microphylla Turcz polysaccharide (PMTP) and investigate the improvement of different PMTP concentrations (4, 6, 8, 10, and 12 wt%) on the PMTP/CS composite gels' properties. PMTP is an acidic heteropolysaccharide with →4)-α-D-GalpA-(1→ and →4)-α-D-Galpa-6-Ome-(1→ as the backbone structure. And PMTP transformed the gel's framework from the lamellar structure of CS gel to 3D porous network constructed by connected nanofibers. This resulted in the increase of surface area from 11.28 to 89.72 m²/g and reduction of pore size from 5.76 to 0.52 μm. Moreover, the mechanical properties of PMTP/CS composite gel was significantly improved 17.9 times higher than that of CS gel. Accordingly, the water holding, swelling, rheology and thermal stability of PMTP/CS gel were further improved. Study on gelation mechanism proved that the formation of composite gel's 3D network was mainly dominated by electrostatic interaction. Finally, Caco-2 cell assay in vitro confirmed the excellent cytocompatibility of PMTP/CS gel. In conclusion, this work provides a scientific reference for the design of bioactive polysaccharide composite gel for food engineering field.