Selenium Bioaccumulation in Sanghuangporus sanghuang: Source-Specific Regulation of Fruiting Body Development, Selenium Speciation, and Nutritional Quality

Sanghuangporus sanghuang (S. sanghuang) is an important medicinal mushroom rich in bioactive compounds. Selenium (Se) biofortification may further enhance its functional value and industrial profitability; however, evidence-based guidance on Se source selection and dosage for production remains insufficient. Using the strain “Sanghuang Hu2”, we compared sodium selenite, nano-selenium (nano-Se), and selenium-enriched yeast (Se-yeast) at different supplementation levels and comprehensively evaluated their effects on mycelial growth and fruiting body development, Se accumulation and speciation, and nutritional quality. The responses of S. sanghuang were strongly Se-source-specific and concentration-dependent. Se-yeast caused the least inhibition of mycelial growth while achieving the highest Se uptake and biotransformation efficiency. During bag cultivation, supplementation with 15 mg/kg Se-yeast significantly increased single-bag yield and biological efficiency without prolonging full colonization time and exhibited superior input cost performance. This treatment enabled an extremely high proportion of organic Se accumulation (>99.5%), dominated by selenomethionine. Moreover, Se-yeast markedly improved crude protein, crude polysaccharides, and total amino acids in fruiting bodies, with lysine showing the largest increase. Overall, considering growth and yield, Se accumulation/speciation, nutritional enhancement, and economic feasibility, Se-yeast is the optimal Se source for Se-enriched Sanghuang, with a recommended dosage of 15 mg/kg.