Study On Mutagenesis Selection And Cultivation Condition Of Selenium-enriched Yeast With Ultraviolet

Selenium is an essential trace element of animals,which has a great deal of biological effects.Selenium is an essential component to keep the activity of glutathione peroxidase which can catalyze glutathione participating peroxidation to get rid of the toxicity of peroxide.However the absorption ration of inorganic selenium is low but high toxicity.Yeast is a good carrier of trace element because of its strong adsorption to trace element.It can convert the inorganic selenium to organic selenium,which can improve the adsorption ration of selenium and lower its toxicity. Yeast is a favourable microprotein source,because it contains abundant protein and vitamin B.So the key to obtain high yield selenium-enriched yeast is a good strain and its suitable cultivate condition.The experiment purpose to obtain a high yield mutant strain utilizing uviolize mutagenesis and resistance screening,and search for optimal incubate condition of it.The experiment take Candida tropicalis 1254 as original strains,through uviolize mutagenesis,the lethality rate curve of yeast shows "shoulder",videlicet the lethality rate of yeast is lower when the yeast undergo low dose radiation and higher when undergo high dose radiation.With duration of radiation increasing,the rate increase gradually.However until a certain degree the rate will cut down.20 mutation strains which grow rapidly and the colony of them are big,are inoculated in flat plate with different density of Se⁴⁺.6 strains whose ability to bear high density of Se is higher was obtained.Y-5 mutation strain was obtained,after advanced screening.Results demonstrated:biomass and content of Se increased from 0.619 g/100mL,688mg/kg to 0.779g/100mL,1252mg/kg separately.The cultivated condition of Y-5 was find out utilizing a single-module experiment:the optimized medium of 11B⁰ is beer wort culture,fermented time is 35h,temperature of cultivate is 28℃,content of Se in medium is 20μg/ml,time for add Se is 11h,dose of inoculation is 10%,the volume of medium is 60ml.Orthogonal experiment was carried out,after 3 factors which affected the content of Se higher.Finding out that the optimized combination is that: content of Se in medium is 20μg/ml,fermented time is 35h,dose of inoculation is 10%.In this condition the biomass of Y-5 increased for 58%,content of Se 74.87% and reached 1343mg/kg.After cultivate for 5 generations,the performances of Y-5 becomes stable.This research assess the content of Se of Se-enriched yeast,results demonstrate that content of organic Se of Y-5 reach up to 93.6%,while that content of organic Se of original strains is 80%.