Hydrogel Design Based on Bacterial Exopolysaccharides: The Biomedical Promise of Levan

Bacterial exopolysaccharides have emerged as versatile biopolymers for the design of advanced hydrogels with adjustable physico-chemical, mechanical, and biological properties. Among these, levan, a fructose-based exopolysaccharide synthesized by various microbial species, has attracted increasing attention due to its unique structural features, high biocompatibility, and inherent bioactivity. This review provides a comprehensive overview of hydrogel systems derived from bacterial exopolysaccharides, with a particular focus on levan-based hydrogels. We discuss the molecular structure, synthesis pathways, and physico-chemical characteristics of levan that underpin its hydrogel-forming ability. Emphasis is placed on design strategies, including chemical modification, crosslinking approaches, and composite formation, that enable fine-tuning of mechanical strength, swelling behavior, and degradation kinetics. This review further highlights biomedical applications of levan-based hydrogels, encompassing drug delivery, wound healing, rejuvenation, tissue engineering, regenerative medicine, and bioprinting, while addressing current limitations and future research directions. By elucidating the structure-function relationships and emerging fabrication methodologies, this review underscores the biomedical promise of levan as a sustainable and functional biopolymer for next-generation hydrogel technologies.