Selenium bioaccumulation and associated nutraceutical properties in Calocybe indica mushroom cultivated on Se-enriched wheat straw

Calocybe indica was cultivated on wheat straw enriched with various concentrations of sodium selenite (Na2SeO3), (2.5-40 μg/ml). The content of selenium (Se) in fruit bodies increased linearly by increasing the amount of Na2SeO3, although the biomass yield inhibited above 5 μg/ml. The fruit bodies accumulated inorganic Se into organic forms by integrating the Se into proteins (56%-68%), polysaccharides (22%-29%), and nucleic acids (1.4%-2.7%). Maximum protein content (25.31 g/100 g) was observed in fruit bodies harvested from the substrate enriched with 10 μg/ml Se. Amino acid profiling revealed the highest value of glutamic acid (4.73 g/100 g), followed by aspartic acid (1.80 g/100 g), and glycine (1.61 g/100 g) at 10 μg/ml. The Se enrichment also enhanced the total phenol, free radical 2,2-dipheynl-1-picrylhydrazyl (DPPH) scavenging activity and ferric reducing power (FRAP) of methanolic extracts of fruiting bodies to almost double of their contents. The principle component analysis (PCA) illustrated close correlations amongst the biomass yield, polyphenols, and antioxidant activities at 5 μg/ml concentrations of the Se.