Abstract: The objective of this study was to determine the selenium speciation distribution, nutritional quality and antioxidant enzyme activity of Agaricus bisporus growing on mushroom beds with different amounts of selenium salt (Na2SeO3). The selenium content and speciation distribution were analyzed by atomic fluorescence spectrometry (AFS). The soluble protein, total sugar and malondialdehyde (MDA) contents as well as the activities of superoxide dismutase (SOD) and hydrogen peroxidase (CAT) were measured using non-Se-enriched A. bisporus as the control. Results showed that the addition of Na2SeO3 led to a significant (P < 0.05) increase in selenium content in the fruit bodies of A. bisporus. Protein-bound selenium accounted for 77%–87% of the total organic selenium, demonstrating protein to be the main carrier of organic selenium. The addition of 40 mg/kg selenium to the compost resulted in an increase in the contents of soluble protein and total sugar compared to the control group, whereas a significant decrease in the two parameters was observed at higher concentration of selenium. With the increase in added selenium concentration, the contents of free amino acid and MDA and SOD activity were increased while CAT activity was reduced. These results showed that the optimal range of selenium concentration could enhance the selenium content of A. bisporus, thereby improving the nutritional quality and physiological properties.

Key words: Agaricus bisporus, selenium, speciation distribution, nutrient quality, antioxidant enzyme activities