Isolation of Indigenous Selenium Tolerant Yeast and Investigation of the Relationship Between Growth and Selenium Biotransformation.

Purpose: Organic selenium compound such as selenomethionine plays a significant function in the response to oxidative stress. Saccharomyces cerevisiae have the ability to accumulate selenium and selenium biotransformation. Selection of indigenous selenium tolerant yeast is our goals. The relationship between cell growth and selenium biotransformation was also investigated. Methods: The screening of the yeast cell was carried out at two steps in order to select yeast with high capacity for resistance and accumulation of selenium. The isolates were selected according to produced high biomass at different concentrations of selenium. Secondly, best yeast strains from previous step were grown in presence of 25 mg/L of sodium selenite and organic selenium content was measured. Results: The S17 isolate showed had maximum organic selenium accumulation (2515 ppm) and biomass production (2.73 g/L) compared to the other isolates. The biomass production and organic selenium accumulation of the S17 during 120 hours was shown a direct relationship between growth and biotransformation. Conclusion: This increase in organic selenium content was achieved with yeast screening. It is interesting to know that organic selenium has high bioavailability and low toxicity compared with inorganic selenium. Therefore, finding yeast strains which are resistant to selenium can be very helpful in cancer prevention.