Preparation, Structural Features, Bioactivities, and Food Application of Oyster Mushroom Polysaccharides: A Review

Water-soluble oyster mushroom polysaccharides (OMPs) are multifunctional biopolymers with growing relevance in food and health-related applications. This review summarizes recent progress in the extraction, purification, structural features, biological activities, and food applications of OMPs, with particular emphasis on tentative structure-activity relationships constrained by heterogeneous experimental evidence. Conventional and emerging extraction approaches, including hot water, enzyme-assisted, ultrasound-assisted, and microwave-assisted methods, are compared in terms of yield and structural integrity. The monosaccharide profiles of OMP fractions vary considerably across different preparation conditions: glucose is universally the dominant component (17.78%-100%), followed by mannose (3.60%-40.34%) and galactose (3.09%-100%), with this compositional variation largely driven by extraction approaches, purification procedures, and fractionation strategies. Water-soluble OMPs are mainly β-glucans with β-(1→3)(1→6)-linked glucose backbones, while small amounts of galactans occur in certain fractions. A wide range of in vitro and animal assays report antioxidant, antitumor, anti-obesity, immunoregulatory, and gastrointestinal protective capacities of OMPs, yet these biological outcomes are dependent on OMP purity, molecular weight range, experimental dosage, and cell/animal model systems. Substantial in vitro and in vivo evidence confirms that OMP bioactive potency closely correlates with monosaccharide composition, molecular weight profile, and functional group distribution. Chemical modifications (e.g., sulfation, phosphorylation, selenization) can further boost OMP bioactivities. In food systems, β-(1→3)/(1→6)-glucan-rich OMPs have been used as stabilizers and texture modifiers. Despite progress, challenges remain in large-scale production, structural standardization, and mechanistic elucidation. Future studies should integrate advanced analytical techniques, multiomics strategies, and artificial intelligence (AI)-assisted modeling to facilitate rational design and industrial application of OMP-based functional materials.