Study On Brewers Yeast With High Level Of Bioactive Selenium-enriched

Selenium is one of the necessary elements to maintain the normal life activity of human's body. The use of selenized yeast as enriched selenium supplements in human nutrition has become a topic of increasing interest over the last decade. This subject used the beer yeast of laboratory as the original strains, strains were filtered for the resistance to the Selenium and optimized the culture conditions of the Se-rich , and by a series of training methods made the ability of selenium-riched had a great increase ,such as handled of the cell wall using a complex enzyme (snail-enzyme), ultrasound treatment in the cell membrane and increased pressure in the culture process, and it laid a good foundation for the further applied to industrial production.The three brewers yeast strains were filtered for the resistance to the Selenium with the method of flat-panel colony counting. Through detected their biomass and selenium intake rate in the medium containing the sodium selenite solution, and the strain 362k had higher biomass and resistance to the sodium selenite. The experimental conditions of the method for detecting the selenium——the reduction of methylene blue was improved through the single factor and orthogonal experiment, and the result showed: As the light was weak, the reaction temperature was 32℃and formaldehyde added quantity was 1mL, the reaction speed was appropriate to time, linear good, and sensitivity was high. The Se-riched culture conditions for the strain 362k were optimized through single factor and orthogonal experiments and confirmed its optimal culture conditions: the temperature was 28℃, the concentration of sodium selenite added was batch to 20μg/mL, the vaccination was 10% (v/v), running speed was 200r/min, and cultured for 48h, the 362 k's growth conditions, biomass and Se-enrichment capacity was best. In this optimal conditions, selenium yeast biomass (dry weight)could up to 8.486g/L, the total selenium content reached 706.423μg/g dry cell, including organic selenium was 642.916μg/g dry cell, the conversion rate reached 91.01 percent.It could be showed that the beer yeast's ability of transforming the inorganic selenium to organic selinum was strong through the optimization of culture conditions, it had reached more than 80 percent. So the selenium intake became a critical factor of selenium-enriched rate. In this issue used the three methods to increase the intake of selenium following: the treatment cell wall with compound enzyme, ultrasound treatment and compression culture, thus increased its total selenium content and content of organic selenium. The results showed that: when cultured for 36h, adding the enzyme was the best, the total selenium content and content of organic selenium had increased significantly, an increase of 10.4 and 12.8 percent, respectively; when cultured for 36h, dealing with the cell by ultrasonic was effective, the total and organic selenium content had increase about 12.4% and 15.4% than no ultrasound treatment, and biomass remained basically unchanged. The total and organic selenium content reached 820.84 and 746.22μg/g dry cell when decked in 12h with pressurized culture, the increase rate reached 19.25 and 24.50 percent respectively.