| Selenium and Chromium are essential micronutrients both for human beingsand animals, they are important to the physiological well being of the human body.According to research, the absorption ofmicronutrients in the diet has something todo with its chemical structure. Free micronutrients are not easily absorbed, Howeverthe re may be some toxicity. Usually the inorganic form of micronutrients is not asbeneficial as organic micronutrients, consequently, it has now become a hot topic ofhow to trans- form inorganic micronutrients into organic ones. Yeast is characterizedby rapid growth, short fermentation and high efficiency in absorbing micronutrients.It's an ideal substance for transforming inorganic micronutrients into organic ones. Atthe moment, a lot of research is being done at home and abroad, about yeast's abilityto gather single micronutrient. Yeast which is rich in iron, zinc, chromium andselenium has been developed, but research has failed to find a type of yeast whichcontains two or even more micronutrients. More than ten micronutrients are essentialfor human beings. Some diseases are not only due to the lack of one single micro-nutrient; for example, a selenium deficiency may lead to myocarditis. According toresearch done in the past few years, low levels of selenium cannot result in theaforementioned disease. Myocarditis probably has a lot to do with the abnormality ofother micronutrients among them, low chromium is an important factor. Therefore, ifthe yeast contains two or more micronutrients together, it will be viable from aneconomical as well as a health point of view.This experimental research begins with the growth of a beer yeast in the lab ofScience and Technology Institute of Hunan Agriculture University, plans to explorethe ideal conditions for growing a beer yeast which is rich in selenium andchromium. This experiment is devided into three main parts: Firstly, finding idealconditions to grow a beer yeast which is rich in selenium. Secondly, finding ideal conditions to grow a beer yeast which is rich in chromium, Thirdly, finding idealconditions to grow a beer yeast which is rich in Se and Cr. After many single-factor-attributed and orthogonal experiments, it comes to conclusion that the idealconditions to grow beer yeast which is rich in Se, Cr and Se and Cr together are asfollows: Take malt juice as culture medium, 30 degrees, pH5.0, the leaven inoculatesmeasures up to 8％, adopting a step-by-step way to add Na2SeO3(0h30％, 6h70％)150mg/L, culture it for 48 hours with rotational speed of 200r/min in a shaking bed,with this we get yeast which contains Se 971μg/g, organic Se takes up 93.5％. Idealconditions to grow a beer yeast which is rich in Cr is that with the temperature of 30degrees, pH5.0, leaven inoculates of 10％, add CrCl3.6H2O(0h30％, 6h70％)step bystep to make its density reach 200mg/L. culture it for 48h with a rotatiofial speed of200r/min in a shaking bed, then we get yeast which contains Cr 921μg/g. organic Crtakes up 91.5％. Ideal conditions to grow a beer yeast which is rich in Se and Cr is totake malt juice as culture medium, with sugar density of 8°Bx, take yeast grease withdensity of 0.4％as the source of nitrogen, salt density of Se 50mg/L, Cr50mg/L, theamount of inotation measures up to 10％pH6.0, culture them for 36h with a rotationalspeed of 200r/min. With this method we get yeast which contains Se and Cr 509μg/gand 518μg/g respectively, organic Se and Cr takes up 93％and 91％respectively.
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