There are about more than 1,500 different species of yeast that can reach up to 3 to 7 and even 40 micrometers in size. Yeast is a big part of our world, it can be found in many of our foods like alcohol beverages, breads, fruits, other food products. It can also be found in soils, plants, and insects. Yeast can survive with or without oxygen and can continue to spread if it fits the environment. Yeast is also a good nutritional supplement with many rich vitamins and proteins.
Yeasts is part of the kingdom fungi, which also contains mushrooms, mildews, and molds. There are about 1,500 species of yeast, that can measure up to 3 to 7 micrometers and some can reach up to 40. You can find Yeasts mostly in sugar- rich places, like flower nectars and fruit surfaces. Yeasts has the ability to ferment sugar making them a big part of the human world, such as baking bread and making alcohol beverages, this is from the yeast species called Saccharomyces cerevisiae. Yeast are unicellular organisms with most species divided into two phyla called Ascomycota and Basidiomycota, and over 100 genera. Yeast can become a string formation connected by the budding cells called pseudohyphae, or seen in most molds called true hyphae. They reproduce asexually by budding and rely on the surroundings to survive. They are an important part of our ecosystem as decomposers.
Yeast is also fed to animals in the form of mash or other byproduct forms. There are about 50,000 species of fungi, but only 60 different kinds of yeast relating to 500 different species of yeast. Yeast is all over the environment it can also be found in silages, hays, grain by-products, sometimes found in soil and water.
Yeast performs asexual reproduction of budding or fission. In fission the yeast parent cell divides into two equal cells. Yeast mostly reproduce with budding, which is when a bud or protrusion, which is the daughter cell made by the parent cell. The Parent cell of the nucleus is divided into a daughter nucleus and is made to a daughter cell. The Bud will keep on growing until it separates from the parent cell forming a new cell. 
Some yeast species are reproduce sexual reproductive cycles. The Yeast cells can be either diploids which means has homologous one sets of chromosomes or it can be haploids which will contain two sets of chromosomes. Yeast cells will die if it is under high stress conditions or nutrient depletion. Mating of Yeasts happens through haploids, which is the a or alpha depending on the difference. 
Yeast clones can produce by budding when the environmental times are good. Even in stressful times Yeasts can lay dormant till the surroundings of the area get better. The Yeast involves asexual budding and it is dependent to its surroundings of conditions. Yeasts really usually likes the different temperatures and acidity. It really thrives in warm moist places that are low in carbon dioxide and high in oxygen. 
Yeast can survive in places with or without oxygen. It can be found in breads, dough or while preparing the flour mixtures and other wine products. Only few wine use natural yeast from Grapes to ferment their wines, but now wines depend on pure culture yeasts to help make their wines. Overall yeast is in many of the foods and drinks that we put into our bodies. 
There are many different kinds of yeast grown for nutritional purposes, the first kind of yeast is the Primary Dried Yeast. It is propagated on sugar substrates, it is dried at a high temperature so it killed the yeast cells inside, then sold to food industries. Another kind of yeast is Brewers Dried Yeast after the beer is fermented the yeast is also dried at a high temperature to kill the yeast cells then sold for food products. Third kind of yeast is Torula Dried Yeast it is grown on waste water, which is called sulfite liquor in other terms then feed to the market industries for foods. The fourth kind of yeast is Whey Yeast, which has been used to make whey lactose from Kluyveromyces marxianus. Whey yeast became a big problem so its use was stopped, but then it started to appear in food ingredients after a while. The last kind of yeast is the Whole Yeasts it contains proteins, peptides, vitamins, and minerals in the cell. 
Yeast can be found in many places with lots of sugar like in fruits such as apple, peaches, grapes. Also it is involved in many beer and wine products. You can find them in many different breads and in doughs of the bread. 
There is also a Yeast that produces "Yeast infections". It can also be found in the vaginal area or other parts of the body that would cause it to make a rash (diaper rash) and throat and mouth thrush. 
Uses in Foods and Nutrition
Yeast is in many of the products we eat and drink today. The First one is beer it makes it produce larger amounts and ferment sugars making it a crispier taste for the beer. Sodas and root beers can also sometimes produce yeast but mostly it turns it into a sugar drink. The Second product yeast is used for is it is in many wine products. In making wine the yeast is already in the grape juice it transforms it into sugar. Another thing yeast is good for is in baking bread. The potatoes, eggs, and sugars in the dough of a bread makes yeast grow faster. But salt and fats will slow down the growth speed of the yeast. Yeast is known for really good in nutritional supplements. For example it is high in proteins and vitamins like b- complex. There are lots more minerals in yeast for nutritional supplements, it is low in sodium and fat. 
Yeast can also be known to spoil foods if yeast is in it. But it is in most of our foods like fruits, breads, alcohol, sodas, and many distilled beverages. 
There are lots of Yeast vitamins to take because it has a high source of vitamin B, folic acid, and niacin. It also has 50 percent protein in it which is good for the muscles. 
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- Yeast Multiple Authors. Multiple Publishers.