Biotransformation of Selenium in Yeast-Speciation and Nanostructural Analysis

Selenium (Se) is an essential trace element for human and animal health, and its deficiency in the diet can lead to metabolic disorders. Se-enriched yeast could be an alternative Se supplement for humans. This study aimed to evaluate the bioaccumulation, the biotransformation, and the production of selenium nanoparticles (SeNPs) in Saccharomyces cerevisiae ATCC 7090 as a conventional yeast compared to Rhodotorula glutinis CCY 20-2-26. Identifying selenium compounds and characterizing nanoparticles (SeNPs) formed in their cells using RP-HPLC-ICP-MS and UHPLC-ESI-Orbitrap-MS. In S. cerevisiae ATCC 7090 at the concentration of 10-mg Se⁴⁺/L in medium, selenium in the cells (1559 μg Se⁴⁺/g) accumulated higher amounts than in R. glutinis CCY 20-2-26 (1202 μg Se⁴⁺/g). Additionally, several selenium species were identified in S. cerevisiae ATCC 7090 cells, commonly known in the conventional yeast, whereas only two selenium species were found in R. glutinis CCY 20-2-26. The size distribution of SeNPs was a range of 60 to 180 nm in S. cerevisiae ATCC 7090 and 40 to 260 nm in R. glutinis CCY 20-2-26. Even though the size of SeNPs were comparable to a therapeutic range (≤ 200 nm), SeNPs were less uniform in R. glutinis CCY 20-2-26. Thus, the overall selenium levels and SeNPs produced by R. glutinis CCY 20-2-26 were significantly lower than the conventional yeast (S. cerevisiae ATCC 7090). The content of SeNPs in the biomass of yeast S. cerevisiae and R. glutinis was 13 and 9 µg/g, respectively. The findings highlight these yeasts' biotechnological potential in producing selenium-rich dietary supplements and nanomaterials.