Huangshui polysaccharides from baijiu fermentation by-products: Emerging structures, functional activities, structure-function relationships and green valorization perspectives

Huangshui, a traditionally overlooked by-product from Baijiu fermentation, is now recognized as a rich source of functional polysaccharides (HSPs). Recent studies have demonstrated that HSPs exhibit diverse biological activities, including antioxidant, immunomodulatory, and gut microbiota-modulating effects, primarily determined by their complex structural features such as monosaccharide composition, molecular weight, branching patterns, and chain flexibility. This review systematically summarizes advances in HSP extraction, purification, and structural characterization, emphasizing how extraction strategies influence their physicochemical properties and bioactivities. Special focus is placed on emerging insights into structure-function relationships, particularly how molecular architectures modulate immune signaling and gut microbial ecology. Furthermore, the dynamic remodeling of HSPs during Baijiu fermentation and the pivotal roles of CAZymes are discussed, providing deeper understanding of fermentation-driven polysaccharide diversity. Finally, green bioprocessing and enzymatic valorization strategies are proposed to transform Huangshui from an environmental burden into a valuable bioresource, aligning with sustainable development and circular economy principles. • HSPs possess diverse monosaccharide compositions and glycosidic linkages. • Green extraction and bioprocessing strategies facilitate sustainable utilization of Huangshui resources. • Fermentation and enzymatic transformation contribute to the structural remodeling and diversity of HSPs.