Introduction
The aquaculture sector faces increasing pressure to reduce reliance on fishmeal and soybean meal while maintaining fish performance and health. Fermentation of agricultural side-streams using fungal mycelium offers a promising strategy to enhance nutritional value and introduce functional properties (Kalaiselvan et al., 2025; Nandi et al., 2025; Yegin, 2025). This study evaluated composite mycelium meal (CMM), produced via solid-state fermentation with Ganoderma lucidum, as a sustainable and functional feed ingredient for European perch (Perca fluviatilis).
Materials and Methods
Juvenile perch (initial body weight 35.0 g) were fed four isonitrogenous, isolipidic, and isoenergetic diets in which CMM was progressively included at 0%, 5%, 7.5%, and 10% while maintaining diets isonitrogenous, isolipidic, and isoenergetic through balanced reformulation. These inclusion levels corresponded to soybean meal replacement levels of 0%, 25%, 37.5%, 50%, respectively. The CMM was manufactured from agricultural side-streams identified in prior preference trials, consisting of 80% canola meal, 15% sunflower meal, and 5% sunflower hulls. Diets were tested in triplicate, and the growth trial was conducted in a recirculating aquaculture system over 84 days. Growth performance, nutrient digestibility, organosomatic indices, histology, blood biochemistry, immune parameters, and gut microbiome composition were assessed.
Results and Discussion
CMM inclusion up to 10% did not negatively affect growth performance, feed conversion ratio, or survival. Fish fed higher inclusion levels (7.5–10%) exhibited significantly (P<0.05) increased body weight (85.0 g and 93.2 g ±15 respecitvely) compared to controls (78.5 g ± 15.1). Nutrient digestibility remained stable across all treatments, indicating efficient utilization of the fermented ingredient.
Organosomatic indices and histological assessments showed no adverse effects, suggesting maintained physiological condition. Blood biochemistry revealed limited diet-related changes, although cholesterol and alkaline phosphatase varied with CMM inclusion.
Immunological analyses demonstrated clear functional benefits: hepatic lipid peroxidation decreased in a dose-dependent manner, while intestinal lysozyme activity and skin mucus protein content increased, indicating enhanced oxidative status and innate immune response.
Gut microbiome analysis revealed diet-dependent shifts in community composition, with reduced diversity but increased specialization at higher inclusion levels, suggesting interactions between diet and microbial ecology.
Conclusion
Fermented agricultural side-streams fermented with G. lucidum mycelium can replace soybean meal in European perch diets up to 50% without compromising growth or health. Additionally, the ingredient provides functional benefits related to immune response and oxidative stress mitigation. This approach represents a promising strategy for improving sustainability and functionality in aquaculture feeds.
Acknowledgment
The project was financially supported by Innosuisse – Swiss Innovation Agency (Grant No. 111.280 IP-LS) and the collaboration with Kidemis AG.
References
Kalaiselvan, P., Devi, N.C., Deepti, M., Devi, A.A., Akamad, K., Dheeran, P., Debbarma, S., Vadivel, D., Rajesh, D., 2025. Solid-state fermentation - a sustainable future technology in aquafeeds? Front. Mar. Sci.12. https://doi.org/10.3389/fmars.2025.1669719
Nandi, S.K., Sarkar, S., Aunkor, Md.T.H., Kari, Z.A., Dey, T., Van Doan, H., Eissa, E.-S.H., Azra, M.N., Siddik, M.A.B., Kabir, M.A., 2025. Applications of solid-state fermented (SSF) diets to improve the growth, organ health, immunity and disease resistance through modulating the transcriptomics and proteomics profile in fish and shrimp. AIMS Microbiol.11, 699–719. https://doi.org/10.3934/microbiol.2025029
Yegin, S., 2025. Solid-state fermentation as a strategy for improvement of bioactive properties of the plant-based food resources. Bioresour. Bioprocess.12, 140. https://doi.org/10.1186/s40643-025-00981-7