Sustainable biosynthesis of exopolysaccharides derived from agricultural byproducts with effective antioxidant properties.

Exopolysaccharides (EPS) are natural macromolecular carbohydrates with good functional activity and physiological activities, but their industrial application was limited by high production costs and unclear structure-function relationships. This study developed a circular economy strategy to produce EPS via microbial fermentation using two food processing wastes (cane molasses and soy sauce residue). After optimizing fermentation medium, the waste-based system achieved an EPS yield of 33.06 ± 0.54 g/L. Two heteropolysaccharides-EPS-2 and EPS-3 were successfully isolated and purified. Monosaccharide composition analysis revealed that EPS-2 primarily consisted of arabinose, glucose, and galactose in a ratio of 65.35:20.82:13.83. In contrast, EPS-3 exhibited a more complex profile containing rhamnose (33.54%), galactose (31.62%), fucose (17.93%), arabinose (13.47%), and glucose (3.44%). Notably, EPS-3 demonstrated higher antioxidant activity than EPS-2. This study successfully demonstrates an innovative waste-to-value conversion strategy that not only achieves high-value utilization of discarded resources but also establishes the fundamental theoretical framework for scalable production of renewable biopolymers.