Bioaccumulation and biotransformation of selenium nanoparticles in soybean and natto, and the bioaccessibility of multi-elements and amino acids.

Soybean is a food crop with strong selenium (Se) enrichment ability. Selenium nanoparticles (SeNPs) are a low-toxic Se source. To develop strategies in SeNPs biofortification of soybean and natto, the effects of Se enrichment and natto fermentation on selenoamino acids, mineral elements, free amino acids, γ-polyglutamic acid, nattokinase, and bioaccessibility were investigated. Soybean grains were able to convert SeNPs into selenomethionine (SeMet). Selenium enrichment and natto fermentation influenced the enrichment and distribution of multi-elements in soybean, as well as the composition of free and bound amino acids. Selenium enrichment had no significant effect on the bioaccessibility of amino acids. After natto fermentation, the bioaccessibility of SeMet, Fe, Mn, Cu, and Zn in the gastrointestinal tract increased significantly by 10.1-18.9 %. These findings indicate that SeNPs can enhance the Se content of soybean grains, and natto fermentation can further improve the nutritional quality of Se-enriched soybean.