Beta-glucan-enriched diets improve immune function, antioxidant activity, and survivability in challenged oysters

• Beta-glucans derived from mushroom waste enhance immune responses and resilience in Crassostrea gigas. • Treatment with beta-glucans leads to increased protein levels and antioxidant activities in oysters. • Beta-glucans demonstrate bacteriostatic properties, potentially extending the shelf life of seafood • 4. The study oDers a sustainable alternative to traditional methods, advancing aquaculture practices. Beta-glucans are bioactive polysaccharides with immunomodulatory and hydrocolloid properties. This study explores the potential of beta-glucans extracted from mushroom waste to enhance oyster ( Crassostrea gigas ) immunity and quality, providing a sustainable alternative to conventional aquaculture interventions. Beta-glucan supplementation led to a 100% survival rate in treated groups compared to 70% in the bacteria-only group (p=0.024). Flow cytometry revealed a significant reduction in viable hemocytes in the beta-glucan group post-infection, suggesting modulation of inflammation. Protein content in gills, mantle, and digestive tissues increased by up to 2-fold in beta-glucan-fed oysters versus controls. Antioxidant activity, assessed by FRAP assay, was 25-40% higher in the mantle and digestive tract if beta-glucan groups. Bacteriostatic assays demonstrated a marked reduction in Vibrio sp. Counts in tissues, particularly in the digestive tract, with bacterial load similar to uninfected controls. These findings highlight the dual functionality of beta-glucans as both immunomodulators and hydrocolloids, with implications for improving aquaculture sustainability and food safety. Further research should explore feeding behaviour, gut transit time, and nutrient absorption to optimize beta-glucan application in commercial shellfish production.