Breeding Of Se-enriched And High-yield Of Zymosan Yeast Strain And Optimization Of Fermentation Conditions

As an important component of some enzymes of anti-oxidant (glutathione peroxidase) and selenium-β protein,Selenium has been recognized as an essential microelement, with improving immunity, anti-oxidant, stay-caducity, anti-cancer and so on. Deficiency of selenium will directly affects the function of heart, liver, skeletal, ocular, prostate and other important organs.According to incompletely statistics, about42countries or regions in the world are short of selenium. Chinese Soclety of Nutrition recommends that the standard of intake of selenium daily is50-250μg for adults, but2/3regions of China are lower than the standard. The content of Se in natural food is very low, and it is very difficult to reach the requirement, the toxicity of inorganic selenium supplementation is high, so organoselenium supplement production by plant and microorganism has been paid more and more attention in recent years, the study on this domain is also more and more.Yeast is an excellent fermentation carrier,it is safe and innocuity, the fermentation is short、simple and efficient.zymosan is one component of the yeast cell wall,which can improve the activity of macrophage, anti-tumor, enhance immunity and these functions are similar to selenium, as a primary metabolite, there are not antagonism between zymosan and organoselenium as secondary metabolite, So we can product antagonism and zymosan at the same time in one fermentation. We take yeast for fermentation.In this study,we chose three yeast strains as the original strain which conservancy by our laboratory. First,we do a survivability sieve experiment with high selenium concentration (150mg/L) in the culture medium, then mutagenesis by UV (ultraviolet)-DES (diethyl sulfate) tautologically, finally we picked two strains with best phenotype. we assay one strain’s ability to selenium-enriched and zymosan, the results show that the selenium-enriched ability of mutant were increased by38.4%and50.7%, the crude zymosan ability were increased by11.7%and15.2%, the biomass also increased(selection80mg/L), these proved breeding were successful. At last,by using RAPD (random amplified polymorphic DNA) technology, we proved the mutant and the breeding were successful at the level of molecular biology. Then we did some experiment to determine the best fermentation conditions:loading90mL/250mL, inoculation3%, PH is natural PH, temperature30℃, speed150r/min, cycle30h, selenium30mg/L. Medium:Malt Extract3%, Yeast extract0.4%, Ammonium sulfate0.2%and Potassium dihydrogen phosphate0.3%. In these conditions, OD value reached0.542, the total selenium content reached984.3μg/g.At last we do a Fermentation with5L fermentor, the dry yeast reached11.5g/L, selenium content reached952.2μg/g, crude zymosan reached11.4%.