Preparation Of Selenium Enriched Yeast With High Biomass And Performance Improvement Study

Selenium is one of the essential elements for the normal physiological function maintenance in human body.It has excellent effect in cancer prevention,liver protection,cardiovascular regulation and thyroid hormone maintenance.Therefore,it is of great significance to develop selenium enriched technologies and products for human selenium nutrition intervention.Saccharomyces cerevisiae can transform available selenium from inorganic form into highly active organic form with their naturally abundant enzyme transformation system.The characteristics of selenium enrichment and nutrients synthesis make it an ideal dietary selenium supplement.In this paper,the MY-02 strain was isolated from the mutants of a normal Saccharomyces cerevisiae strain with UV radiation and selenium salt pressure.With the mixed selenium sources,the physiological and molecular mechanisms of improved selenium enrichment performance in yeast were discussed.Studies from above may provide a feasible reference for the follow-up study of selenium enriched yeast and future development.The main contents and research conclusions obtained as follows:(1)A high-performance selenium enriched strain MY-02 was obtained from the mutants of a normal Saccharomyces cerevisiae strain(CICC 31105)with UV radiation and selenium salt stress.The results showed that the conditions of excellent Se-enriched performance were as follows: concentration and addition time of sodium selenite were 35 mg/L and 8 h,and the optimal incubation time was 30 h.The total selenium content was 3129.40±50.12 ?g/g and the biomass was improved to 6.37±0.21 g/L under these incubation conditions.That is,the potential the selenium content was 2 times higher than that of the original strain.(2)Based on the regulation of sodium and potassium ions,the selenium enrichment performance of MY-02 strain was optimized by mixed selenium source treatment,and the physiological mechanism was explored.According to the standardized selenium production analysis,strain presents superior selenium enrichment ability at the ratio of potassium selenite and sodium selenite was 2:1(w/w).The conclusion was verified with the growth trend and extracellular p H level of the yeast.To analyze the potential physiological mechanism of selenium accumulation in yeast cell,SEM?TEM-EDS and FTIR technologies were used to observe the morphology and distribution of selenium.Besides,the activity of the key limiting enzyme(selenophosphate synthetase)in selenium metabolism was measured to explain the physiological mechanism of selenium enrichment performance improvement.(3)The sequence differences of strains were determined by RNA-seq technology under different treatment conditions to explore the molecular mechanism of gene expression during selenium enrichment.The results of functional annotation analysis showed that the addition of selenium salt can up-regulate the genes related to extracellular selenium transport and intracellular selenium conversion,focusing on the biological metabolism of amino acid and NADPH.The mixed selenium source based on sodium and potassium ion regulation can upregulate PHO gene family related to selenium transport,and stimulate GSH synthesis pathway,further improving the selenium enrichment performance of the strain.