A multifunctional high-molecular-weight dextran from the sourdough-derived Weissella confusa SR37: Structure and...

Dextran produced by lactic acid bacteria have attracted increasing attention due to their structural diversity and multifunctional applications. In this study, a high-molecular-weight dextran produced by Weissella confusa SR37 from natural sourdough was characterized, and its structure-function relationships were explored. Structural analyses by FTIR, Raman, and ¹H/¹³C NMR confirmed that the polymer is a dextran, an α-glucan predominantly composed of α-(1 → 6)-linked d-glucopyranose units (94%) with a limited α-(1 → 3) branching (6%). SEC-MALLS analysis showed a remarkably high molecular weight of 3.8 × 10⁸ Da and a hydrodynamic radius of 199 nm. Scanning electron microscopy revealed a porous morphology associated with high hydration capacity. Rheological analysis indicated that the polymer exhibits pseudoplastic behaviour at high concentrations, a characteristic of shear-thinning biopolymers. Functional assays demonstrated outstanding techno-functional performance: high water solubility (97.7%), remarkable water-holding capacity (270%), significant emulsifying ability (E24 up to 78%), strong antioxidant activity (up to 87% hydroxyl radical scavenging) and biological activities including antibiofilm inhibition (>65%) and antifungal activity against phytopathogenic spores (up to 84%). These properties may be associated to the structural flexibility and abundant hydroxyl groups of the macromolecule. In conclusion, this work highlights the relationship between structural characteristics and multifunctional properties of a microbial dextran produced by a W. confusa strain, suggesting its potential as a natural, sustainable biological macromolecule for food, pharmaceutical and agricultural applications.