Types of yeast fungi. Yeast fungus in women and men

Yeasts are fungi that have lost the ability to form mycelium. Yeasts do not constitute a separate class of fungi, they do not constitute a separate class, but belong to the 3rd class of higher fungi. 50% of higher fungi are ascomycetes. Yeasts are unicellular fungi. Dimensions - 1-10 microns, average - 5-7 microns. According to their morphology, they are diverse: they can acquire a different shape (oval, cylindrical, sickle-shaped). May form false mycelium.
1. Morphology is determined by the type of vegetative reproduction:
1.1 Budding. Round, ovoid or oval cells appear. With multiple budding, when the cell is laid down in several parts of the cell, a stellate shape can form. As a result of budding without separation of the kidney from the mother's body and continued budding, false mycelium (genus Candida) appears.
1.2 Budding division. The kidney lays at the base of the cell, as a result of which a pear-shaped (kidney on one side) or fusiform (kidney on both sides) can form.
1.3 Division. Normal division is rare, in this process 1 mother cell gives 2.
2. Asexual reproduction. It is carried out with the help of special cells and spores - ballistospores, endospores. The ballistospore is formed on a special outgrowth - the sterigma, after which it is thrown into the distance. Endospores are laid inside the mother cell (2-10 in 1 cell).
3. Sexual reproduction. They can be carried out in the haploid and diploid phase. Most yeasts are diploid. For everyone there is a type of development.

Development cycle of haploid yeast
Two haploid cells merge with each other, go through the stage of plasmogamy and karyogamy, resulting in the formation of a cycloid zygote. It divides mitotically, fasting - with the help of reduction division. As a result, n-number of ascospores containing a haploid set of chromosomes is formed inside the mother cell. They germinate and give rise to a haploid vegetative cell.

Development cycle of diploid yeast
A vegetative diploid cell undergoes reduction (meiosis). As a result, ascospores containing a haploid set of chromosomes are formed under the maternal membrane. Ascus bursts, haploid ascospores come out and merge with each other. They go through the stage of plasmogamy and karyogamy, resulting in the formation of a diploid zygote. It reproduces by budding and thus restores the population of diploid yeast.

Yeast classification according to Kudryavtsev (1952)

1. Class Ascomycetes (Ascomycetes).
1 family - Saccharomyceteceae (17 genera), genus Saccharomyces:
- S.cerevisiae (alcohol production, starch processing, bread production);
- S. Carlsbergensis (in breweries);
- S.vini (in winemaking);
- S.minor (for dark types of bread);
2 family Shizoaccharomyceteceae (2 genera), genus Shizoaccharomyces:
- Schizoes pombe (in beer production);
- Sch. Mosquensis (in winemaking);
3 family Saccharomycodaceae (4 genera).
2. Class Fungi imperfecti.
1 family Cryptococcaceae:
- 1 subfamily Cryptococcaideae;
*1 genus Cryptococcus;
* 2 genus Torulopsis (kefir, winemaking);
* 3 genus Candida (BVK, causative agent of mycoses);
* 4 genus Pitorosporum (on human skin);
* 5 genus Brettonomyces (a pest of winemaking);
- 2 subfamily Trichospoiceae (10 genera):
* 1 genus Trichosporon;
- 3rd subfamily Rhodotoruloide:
* 1 genus Rhodotorula.

mold mushrooms

(micromycetes)
These are filamentous microscopic fungi. They form a fluffy coating on the surface from their mycelium. They need a certain humidity, temperature and the presence of a certain substrate. Mycelium deeply penetrates the substrate.
In a systematic sense, mold fungi are heterogeneous and belong to both higher and lower fungi (ascomycetes, fungi imperfecti, lower - zygomycetes). Zygomycetes - r. Mucor, r. Rhizopus.
Characteristic. Mucor - on dense PS forms a felt coating. The body is represented by celocyte mycelium. Hyphae arise from the mycelium - sporangiophores with sporangia, on which spores are formed. Rhizopus - differ from Mucor in that sporangiophores are formed on the mycelium in bunches.


Folk meaning of mushrooms and yeast
Widely used in biotechnological (b / t) in the production of alcohol, beer, wine, etc. In the baking industry, yeast r. Saccharomyces - used in the form of dry live yeast, which are rich in B vitamins and immunomodulators. R. Candida - protein-vitamin concentrates in animal husbandry. In addition, they receive valuable drugs - vitamin D2, lipids, nucleic acids. Enzymes and coenzymes, as well as organic acids. Mold fungi are producers of organic acids (citric acid), antibiotics, etc. Among the fungi there are pests that are pathogenic for humans and animals.

Lecture, abstract. Yeast as a type of fungus - concept and types. Classification, essence and features.

Yeast is a living single-celled organism found in plants and animals. Yeast cells are egg-shaped and can only be seen through a microscope.

What is yeast

If you weigh the yeast and count the cells in them, then there will be about 20 billion cells in approximately 1 g of the substance. Since the human eye is unable to see a 5 micron cell, these organisms have long been one of the most mysterious. Until the middle of the 19th century, mankind knew little about them at all. It was not until 1866 that the microbiologist Louis Pasteur, who devoted his entire life to studying the principles of fermentation, became interested in the process of yeast fermentation using beer as an example. And 15 years later, in a laboratory in Copenhagen, Emil Hansen isolated and purified individual strains of yeast. Methods for cultivating yeast fungi according to the Hansen method are still used.

Yeast cells are living organisms and need air to reproduce. These cells need to be fed to get energy. And their favorite food is anything sweet: sucrose (cane and beet sugar), fructose and glucose (honey, fruits, maple syrup), maltose (starch).

The size of a yeast cell does not exceed eight thousandths of a millimeter. There are approximately 1500 types of yeast. There can be thousands of genetically different strains within a single species, but perhaps the most famous is Saccharomyces Cerevisiae, which is Latin for sugar, fungus, and brewing. More often they are called by more understandable names - brewer's yeast or baker's yeast. Each of these species has certain characteristics, and they determine the scope of yeast. In brewing, for example, different strains are used to produce different types of drink. But the scope of this substance is much wider. Yeast is used for the production of many products, they play the role of flavoring agents, and have also found application in pharmacology, animal husbandry and other areas.

general characteristics

Yeasts are organisms that need food, heat and moisture to live and reproduce.

As a result of fermentation, they convert sugars and starches into carbon dioxide and alcohol. There are different types of yeast that are beneficial to human health. They can strengthen the immune system, improve digestion, but some cause fungal infections.

The most famous types of yeast:

• beer;
• bakery;
• pressed (or confectionery);
• dry;
• fodder.

The discussion around unicellular fungi is not new. Many are interested in what baker's yeast actually is, the benefits or harms of them, some are frightened by their composition according to GOST, so more and more housewives choose not domestic, but French yeast. In fact, if you understand what yeast is, how these microorganisms multiply and how they affect baking, it becomes clear that there is nothing to worry about by and large. Whether these substances are beneficial or, conversely, harmful to the body depends on the amount of their consumption, the sensitivity of the body, and the presence of Candida in the body. In small quantities, yeast can improve health by replenishing B-group vitamins, but an excess of the substance can adversely affect a person.

Studies have shown that yeast cells are very similar to cells in the human body. But while our bodies have tens of billions of cells, yeast only has one.

Man, as scientists say, is a eukaryotic organism. In simpler terms, this means that all of our genetic material is contained in the cell nucleus and mitochondria. According to the same principle, nature created yeast, but bacteria are already representatives of prokaryotic organisms. And due to the fact that yeast is single-celled, it is easier for scientists to study their structure, properties and life stages. And from the point of view of structure, metabolism, of all biological models, it is yeast that is closest to a person. In addition, this fungus is the first eukaryotic microorganism whose genome scientists have deciphered by studying the exact sequence of all its 16 chromosomes.

The importance of the study of these microorganisms is also evidenced by the fact that over the past 15 years, the Nobel Prize in Medicine and Physiology has been awarded to yeast researchers twice. Using human genes in the fungus, scientists test the effectiveness of new drugs, study the specifics of certain diseases.

Most of the research has focused on the potential use of yeast in the healthcare and food industries. Meanwhile, scientists conducted other experiments. For example, not so long ago it became clear that some of the yeast strains can serve as the basis for the creation of biofuels for transport. By the way, a significant proportion of the insulin created by chemists to treat diabetes was produced with the help of yeast.

But this is not all that a person has to learn about yeast. This, at least, is convinced by scientists involved in the study of these microsubstances.

Life cycle of fungi

It should be noted that the development of yeast cells under different circumstances proceeds differently. And although these substances, from the point of view of biologists, are living organisms, they are so unique that they can live without air.

When the yeast does not receive oxygen, it acts on the sugar and turns it into alcohol. In addition, carbon dioxide is released. This process occurs mainly during baking. As a result of this reaction, energy is released - the dough grows. Meanwhile, this energy is not enough for the yeast to continue to live. In the presence of oxygen, they, nourished by sugar, grow and multiply very quickly, releasing carbon dioxide, water and a relatively (by the standards of a fungus) huge amount of energy.

"Good" and "bad" yeast

Yeast, like bacteria, is necessary for the human body. But the first thing that is important to know about these microorganisms is that there are good and bad bacteria, and similarly with yeast. The fungus can affect organs and tissues, cause allergies and many diseases. Now let's try to understand the types of fungi and understand which ones are useful and which ones should be avoided.

candida albicans

It is said that almost 80 percent of the world's population is struggling with this pathogenic yeast-like fungus, which causes various inflammations in the body. Candida, like all yeast, is a single-celled organism that multiplies rapidly in the presence of a large amount of sugar in the diet. This fungus robs the body of many nutrients, including iron and other minerals, making the blood acidic. Against the background of a sweet diet, candida is activated even more. If this process is not stopped in time, then harmful yeast will practically destroy the digestive and immune systems, and deprive you of vitality. And in return, they will cause frequent headaches, eczema, dandruff, dermatitis, hormonal disorders, vaginal infections, stomach diseases and confusion.

Healthy Yeast

But in addition to harmful ones, there are also beneficial ones. Fungi found in probiotic foods are best for the body. They strengthen the immune system and help fight candida. But also not the best sources of this yeast are products that contain sugar.

Found in almost all probiotics, S. boulardii yeast has many health benefits:

• strengthen the immune system, stimulate the production of antibodies;
• protect the body from the harmful effects of antibiotics;
• helps fight candida.

Another two extraordinarily beneficial yeast strains are Kluyveromyces marxianus var. Marxianus and Saccharomyces unisporus. They are contained mainly in kefir sourdough and play the role of a powerful booster for the immune system. Thanks to these components, kefir has been considered one of the best tonic drinks throughout the world for centuries. In ancient times, it was considered the drink of centenarians, and in Turkish its name sounds like "feel good."

Benefit for health

Yeast is a wonderful ingredient that helps maintain or restore health and beauty in a natural way.

They are present in many foods, dietary supplements, and are also part of many cosmetics.

For many decades, yeast has been the focus of researchers who unanimously recognize the extraordinary nutritional qualities and therapeutic properties of this fungus. And all - thanks to the unique biochemical composition of these organisms. For humans, they serve as a source of amino acids, minerals, vitamins, enzymes and many other useful substances necessary for growth, proper metabolism and strengthening the immune system.

Yeast Benefits

These microscopic substances are a source of nutrients and fiber, many types of nutritional yeast contain, which is usually found exclusively in foods of animal origin. In addition, yeast is an excellent source of vegetable proteins, making it an important ingredient in vegetarian dishes. A high concentration of fiber provides a feeling of satiety for a long time. These elements are extremely important for the smooth functioning of the body. They are equally important for humans, animals and even plants.

For plants

The latter, just, are the object of recent research. As it turned out, yeast can act not only as a food additive, but also as a useful natural fertilizer. Some strains contribute to more efficient absorption of useful soils by plants. In addition, they affect the growth of plants. At the same time, they are absolutely safe "fertilizer". Now scientists are trying to develop an effective yeast-based drug against mold in fruits and other diseases - as a safe alternative to chemical drugs.

Food supplement

Perhaps no one will be surprised by the information that yeast is a useful bioactive supplement used by people to treat and prevent a variety of conditions and diseases.

Probiotic

Yeast as probiotics is a very promising solution. So scientists convince and add that the range of impact on humans of these microorganisms is very wide.

For intestinal flora

Scientists have discovered the relationship between yeast and intestinal microflora, in particular, the positive effect of the fungus on the inflamed intestine.

Beneficial features:

• brewer's yeast contains many vitamins and minerals, including chromium, folic acid, biotin and B-vitamins;
• strengthen immunity;
• normalize blood sugar;
• promote the development of beneficial bacteria in the body;
• yeast Torula - source, and;
• baker's yeast strengthens the immune system.

Possible harm to yeast

An unfortunate side effect of taking yeast can be that it feeds not only beneficial bacteria, but also harmful bacteria such as Candida that cause asthma, gout and other diseases. With an exacerbation or occurrence of candidiasis, it is important to exclude all yeast food from the diet for the period of treatment.

Yeast and Allergies

Yeast, as already noted, is a form of fungus. Most often used for baking and brewing. In this case, brewer's and baker's yeast are used. But besides them, there is also the so-called wild yeast, which can be found in fruits, berries (grapes) and grains.

Usually these microorganisms are well tolerated by humans, but there are people who are intolerant. These are people who are allergic to all types of fungi and mold.

Yeast extract

Yeast extract is a food flavoring used in bread, beer, cheese, soy sauce, and some other foods.

To understand how this substance affects the body, you first need to understand what it is in general.

Yeast extract is made by mixing yeast and sugar under warm conditions. And with the subsequent breaking of cell membranes. Such an extract may be in gel or powder form. The use of yeast extract in products may be referred to as "natural flavors" or "additives" on product labels.

You should know that this extract contains the amino acid glutamic acid. This is the natural form of the amino acid and should not be confused with monosodium glutamate, which serves as a flavor enhancer. And although the yeast extract also affects the taste, it acts like a spice. In addition, it contains a high concentration of sodium. And this should be taken into account for people who have problems with blood pressure or those who, for other reasons, should not abuse sodium. In addition, the extract contains a very high concentration of B vitamins.

But despite all the benefits of this substance, it is important for people with food allergies or sensitivity to yeast to avoid products containing fungus extract. The easiest way to do this is to refuse semi-finished products and ready-made food from supermarkets.

Yeast in food

All products for yeast content can be divided into 3 groups. The first is food that contains fungi under any circumstances. In the second group of products, microorganisms are present only under certain conditions. And the third group is food that does not contain this substance.

The first group includes: bakery products, beer, cider, fruit skins (plums, grapes), grape juice, malt drinks, wine, yeast extract.

The second group includes: cakes, donuts, fruits (overripe), chocolate (some types), soy sauce.

The third group includes a huge number of products from different categories. In particular, you can not worry about the presence of yeast in eggs, seafood, various types of meat, raw nuts, beans, brown rice. You can also avoid excess consumption of yeast if you refuse soy sauce during cooking, and replace vinegar with lemon juice.

List of products containing yeast:

• all fermented (vinegar, alcohol, miso, soy sauce, etc.);
• bakery;
• vitamins B;
• beer;
• berries (blackberries, blueberries, grapes, strawberries);
• canned juices;
• cider;
• dried fruits (figs, dried apricots, raisins);
• jams, jellies;
• mushrooms;
• processed meat (sausage, bacon);
• Black tea;
• olives;
• wine.

Cautions

Yeast can interfere with the effectiveness of some medications. It is also important to avoid dietary supplements containing yeast for people who are allergic to the product or prone to yeast infections.

An important note for diabetics: Yeast can lower blood sugar, so it's a good idea to monitor your glucose levels regularly.

How to make your own yeast

Surely, you wondered what yeast is made of and how this process occurs. Now you will learn how to grow these single-celled mushrooms yourself at home.

beer

Method one. Take 1 glass of water and flour, mix and leave for 7 hours. Then supplement the mixture with a small spoonful of sugar and a glass of live beer (has a shelf life of up to 2 weeks). Leave for a couple of hours. Store prepared brewer's yeast in a glass container in the refrigerator.

Method two. In a glass container, mix 200 g of raisins, milk, warm water and a little sugar. Cover the vessel tightly with gauze (fold in 4 layers and tie). Keep in a warm place for 5 days.

With these recipes, you will create a common nutritional yeast that doctors recommend taking for various diseases. This natural product will help with metabolic disorders, lack of B vitamins, digestive diseases, anemia, atherosclerosis, strengthen the body after flu or tonsillitis. By the way, home-made brewer's yeast is similar in its effect to medications containing these fungi, such as gefefitin.

For baking

Perhaps this happened in every housewife. I wanted to bake pies for dinner, but there is no yeast. But this is not a reason to be upset if you know how to make homemade yeast in the form of a sourdough.

Method 1

From 200 g of flour and a small amount of water, knead a lump of dough, roll in flour and leave for a few of it. When the lump dries, hardens and becomes sour, it can be used instead of store-bought yeast.

Method 2

Peel and boil 10 potatoes, which are still hot, rub through a sieve. Add a tablespoon of flour, the same amount of honey and 25 grams of vodka. Leave the mixture for 2 days in heat. When a foam cap forms on the surface, you can use the sourdough for baking (take only foam).

Homemade yeast cosmetics

The fact that yeast is an effective ingredient in many beauty products has long been known. But not many people know that yeast cosmetics are easy to prepare on your own. Don't know how to do it? Read our recipes.

Yeast Body Mask

Dilute a bag of dry yeast in cream and add 4 tablespoons of honey to the mixture. Leave for 20 minutes. Apply to the body and leave for 15-20 minutes. Wash off with warm water. This mask improves blood circulation, tightens pores, makes the skin supple and smooth.

Hair Care Product

In a glass of kefir, dilute a tablespoon of brewer's yeast. Leave the mixture in a warm place for several hours. Apply to hair and keep for about half an hour. This mask will get rid of dandruff.

Yeast for the face

Dilute about a teaspoon of brewer's yeast in a small amount of kefir. After the mixture has been infused a little in a warm place, and acquires the consistency of liquid sour cream, apply to the skin of the face and hold for about 20 minutes. This tool relieves acne, improves complexion, suitable for oily skin.

Interesting facts about yeast:

1. The optimum temperature for yeast growth is 32.2 degrees Celsius, above 38 degrees the yeast will die.
2. Some strains of the fungus clump together after fermentation (usually during brewing).
3. Dry yeast was invented by the Romans (however, as often happened in the history of discoveries of great things, they did not yet understand that it was dry yeast). The ancients put baker's yeast (in dough) in the sun, dried it, and when necessary they revived it with sugar.
4. The flavor of the beer is determined by the yeast.
5. There are more than half a thousand types of yeast.
6. Back in 1200 B.C. e. knew how to bake yeast breads.
7. Hops, whey, various herbs, oranges, grapefruits, honey drink can serve as raw materials for yeast.
8. In laboratory conditions, about 100 tons of yeast milk can be grown in 2 weeks (then pressed, liquid, dry yeast is made from it).

Many people ask the question: "Yeast is fungi or bacteria." And there is nothing strange in this, because until relatively recently, scientists themselves did not know the answer to this question. Today, there are other discussions about how safe it is to take yeast. And again, the answer is banal simple: safe, if in moderation.

Yeast fungus, the treatment of which is not particularly difficult, is a fairly common disease among females and males. Treatment of yeast fungus must be done in a timely manner, since a yeast infection can cause serious pathologies.

The human body is inhabited by thousands of varieties of fungi and bacteria that form the microflora of various organs. A number of external factors, pathologies and disorders in the human body can provoke the rapid reproduction of yeast and fungi. Among the main factors are:

Only a doctor can identify and determine the presence of harmful microflora. The diagnosis is made after examination and testing. The main symptoms of the disease:

• burning and itching;
• redness;
• swelling;
• white discharge and formations on the mucous membranes;
• rash of a different nature;
• chronic fatigue, apathy;
• pain in the abdomen;
• indigestion, heartburn, constipation;
• neuroses and mental disorders;
• increased sweating;
• severe headaches;
• pain during urination, sexual intercourse.

Yeast can affect both women and men.

A fungal infection (candidiasis) can be transmitted by airborne droplets, through objects and food, as well as through sexual contact.

Fungi begin to actively multiply on the skin and mucous membranes of a person. Doctors distinguish several types of the disease:

• candidiasis of the internal organs (visceral candidiasis), which affects the gastrointestinal tract, respiratory system, genitals and urinary system;
• superficial candidiasis, which affects the skin and nails;
• candidiasis of the mucous membranes, which manifests itself in the form of thrush and stomatitis.

In most cases, yeast fungus is found on the face, armpits and groin. After the detection of pathogenic microflora, the doctor prescribes the appropriate treatment for the fungus.

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Medical treatment

Yeast fungi, which can be treated at home, can be overcome with the following drugs:

• Gynofort;
• Miconazole;
• Fenticonazole;
• Cyclopirox;
• Butoconazole;
• Nystatin;
• Clotrimazole;
• Natamycin;
• Caprylic acid, etc.

Some of these drugs are taken orally. Other medicines in the form of ointments, creams, solutions and suppositories are applied to the skin and mucous membranes. It is necessary to treat candidiasis comprehensively. From external agents, a solution of sodium tetraborate can be isolated. At any stage of the disease, therapy with general strengthening and immunostimulating drugs is additionally prescribed. It will not be superfluous to take lactic acid bacteria or lactobacterin.

Do not forget about proper nutrition and taking probiotics. Probiotics contain lactulose, which is essential for the body to fight disease. The most popular drugs are:

• Candinorm;
• Lactusan;
• Normaz.

carried out using special ointments, gels, varnishes, solutions and sprays. Among these funds, lacquer loceryl can be distinguished. The varnish penetrates deep into the skin and destroys the fungus. In parallel, terbinafine or diflucan drugs are prescribed. With severe inflammation, antibiotic therapy may be prescribed. The dosage of drugs, the frequency and duration of treatment is determined only by the attending physician.

When using combination therapy with Lumexin and Fluconazole. Antimicrobials are prescribed to suppress the growth of anaerobic bacteria. With untimely treatment of vaginal candidiasis, there is a risk of infection spreading to the bladder and large intestine. Treatment of chronic forms can be delayed for many months. Also, the patient should stop smoking and drinking alcohol.

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Folk remedies in the fight against infection

In folk medicine, there are a lot of recipes and recommendations that will help get rid of yeast. From the means of local application can be distinguished:

1. Honey. To prepare the solution, it is necessary to dissolve 1 tablespoon of honey in 0.2 cups of warm water. The solution is rubbed on the affected areas on the skin.
2. Mint and table salt. A mixture of crushed mint and table salt is applied to the affected area for 30-50 minutes.
3. Soda baths. To prepare the solution, it is necessary to dissolve 4 teaspoons of soda and 1.5 teaspoons of iodine in 2 liters of warm water. Take a bath for 5-10 minutes.
4. Carrot juice and whey. Juice or serum is applied to the affected area for 20-40 minutes.
5. Infusion of milkweed will help eliminate the fungus on the nails. An infusion is prepared from the herb. Next, in the infusion, you need to soar your legs or arms.
6. A compress of onion pulp or garlic.
7. propolis solution.

Of the recipes for internal use, they proved their effectiveness:

1. An infusion of dandelion, yarrow, mint, meadowsweet, marshmallow and gentian will help rid the gastrointestinal tract of the fungus. Grind the herbal collection until smooth. Pour 1 cup of water with 1 tablespoon of the collection. Infusion to use fractionally throughout the day.
2. An infusion of wild rosemary, elderberry, fennel and angelica will help with candidiasis of the respiratory tract. The above herbal collection must be crushed to a homogeneous mass. Pour 1 cup of water with 1 tablespoon of the collection. Infusion to use fractionally throughout the day.
3. A decoction of ivy, goose cinquefoil, medicinal chamomile, madder dye and balsamic tansy is prescribed for lesions of the urinary tract. To prepare a decoction, you need to mix all the components of the collection in equal proportions. It is necessary to boil the broth on a small fire. Cooking time is 2-3 minutes. A glass of infusion should be drunk throughout the day.
4. Tea from chamomile and St. John's wort will strengthen the protective properties of the body, and will also have a general antibacterial effect.

Any treatment with folk remedies should be agreed with the attending physician. Doctors advise that to prevent the disease, you need to monitor hygiene, maintain your immunity and eat only healthy food.

Yeasts are eukaryotic single-celled microorganisms classified as members of the fungi kingdom. The first yeasts arose hundreds of millions of years ago, and 1,500 yeast species have now been identified. They are estimated to represent 1% of all described fungal species. Yeasts are single-celled organisms that have evolved from multicellular ancestors, with some yeast species having the ability to develop multicellular characteristics by forming sequences of associated budding cells known as pseudohyphae or false hyphae. Yeast sizes vary greatly by species and environment, typically 3-4 µm in diameter, although some yeasts can grow up to 40 µm. Most yeast reproduce asexually by mitosis, and many do so through an asymmetric division process known as budding. Yeasts, with their single-celled nature, can be contrasted with molds that grow with hyphae. Fungal species that can take on both forms (depending on temperature or other conditions) are called dimorphic fungi ("dimorphic" means "having two forms"). During fermentation, the yeast species Saccharomyces cerevisiae converts carbohydrates into carbon dioxide and alcohols. For thousands of years, carbon dioxide has been used in baking and in the manufacture of alcoholic beverages. Yeast is also a centrally important model organism in modern cell biology research and one of the most thoroughly studied eukaryotic microorganisms. Researchers have used yeast to gather information about the biology of the eukaryotic cell and, ultimately, human biology. Other yeast species, such as Candida albicans, are opportunistic pathogens and can cause infections in humans. Yeast has recently been used to generate electricity in microbial fuel cells and to produce ethanol in the biofuel industry. Yeasts do not form a single taxonomic or phylogenetic group. The term "yeast" is often taken as a synonym for Saccharomyces cerevisiae, but the phylogenetic diversity of yeasts is demonstrated by their placement in two separate sub-kingdoms: Ascomycota and Basidiomycota. Budding yeasts ("true yeasts") are classified in the order Saccharomycetales, in the phylum Ascomycota.

Story

The word "yeast" comes from the Old English gist, gyst, and from the Indo-European root yes-, meaning "boiling", "foam" or "bubble". Yeast microbes are probably among the earliest domesticated organisms. Archaeologists excavating Egyptian ruins have unearthed early grinding stones and baking chambers for baking yeast bread, as well as 4,000-year-old drawings of bakeries and breweries. In 1680, the Dutch naturalist Anton van Leeuwenhoek first discovered yeasts under a microscope, but at the time he did not consider them living organisms, but rather globular structures. Whether yeasts were algae or fungi was questioned by researchers, but in 1837 Theodor Schwann recognized them as fungi. In 1857, the French microbiologist Louis Pasteur proved in his article "Mémoire sur la fermentation alcoolique" that alcoholic fermentation is done with live yeast and not with a chemical catalyst. Pasteur showed that, by bubbling oxygen into the yeast broth, cell growth could be increased, but fermentation was suppressed - an observation later called the "Pasteur effect". By the end of the 18th century, two strains of yeast used in brewing were identified: Saccharomyces cerevisiae (upper fermenting yeast) and S. carlsbergensis (lower fermenting yeast). S. cerevisiae has been sold commercially by the Dutch for bread making since 1780; while around 1800 the Germans began to produce S. cerevisiae in cream form. In 1825 a method was developed to remove the liquid so that the yeast could be obtained as solid blocks. The industrial production of yeast blocks was boosted by the introduction of the filter press in 1867. In 1872, Baron Max de Springer developed a manufacturing process to create granulated yeast, a technique that was used until the First World War. In the United States, natural wild yeast was used almost exclusively until commercial yeast was sold at the 1876 World's Fair in Philadelphia, where Charles L. Fleischmann demonstrated the product and its use, and served the resulting bread.

Nutrition and growth

Yeasts are chemoorganotrophs because they use organic compounds as an energy source and do not require sunlight to grow. Carbon is obtained mainly from hexose sugars such as glucose and fructose, or disaccharides such as sucrose and maltose. Some species can metabolize pentose sugars such as ribose, alcohols, and organic acids. Yeast species either require oxygen for aerobic cellular respiration (exclusively aerobic bacteria) or are anaerobic but also have aerobic methods of energy production (facultative anaerobes). Unlike bacteria, the unknown species of yeast grow only anaerobically (the exclusive anaerobes). Most yeasts grow best in a neutral or slightly acidic pH environment. Yeast grows differently depending on the temperature range in which it grows best. For example, Leucosporidium frigidum grows from -2 to 20°C (28-66°F), Saccharomyces teluris grows from 5 to 35°C (41-95°F) and Candida slooffi grows from 28-45°C (from 82 to 113°F). Under certain conditions, cells can withstand freezing, while their viability decreases over time. In general, yeasts are grown in the laboratory on solid plant media or liquid nutrient media. Common media used for culturing yeast include potato dextrose agar or potato dextrose medium, Wallerstein Laboratories nutrient agar, peptone dextrose yeast agar, and yeast agar or molding agar. Homebrewers who grow yeast often use dried malt extract and agar as a solid growth medium. The antibiotic cycloheximide is sometimes added to yeast growth media to inhibit the growth of Saccharomyces yeast and to grow wild/local yeast species. This will change the yeast growing process. A type of white yeast, commonly known as kam yeast, is often a by-product of lacto-fermentation (or fermentation) of certain vegetables, usually by exposure to air. Although harmless, white yeast can impart a bad taste to pickled vegetables and must be regularly removed during fermentation.

Ecology

Reproduction

Like all fungi, yeast can have asexual and sexual reproductive cycles. The most common mode of vegetative growth in yeast is asexual reproduction by budding. A small bud (also known as a bubble), or child cell, forms on top of the parent cell. The nucleus of the parent cell splits into a daughter nucleus and migrates to the daughter cell. The bud continues to grow until it separates from the parent cell, forming a new cell. The daughter cell created by the budding process is usually smaller than the mother cell. Some yeasts, including Schizosaccharomyces pombe, reproduce by fission rather than by budding, thus producing two equally sized daughter cells. In general, under stressful conditions such as lack of food, haploid cells will die; however, under the same conditions, diploid cells can sporulate, enter sexual reproduction (meiosis), and produce various haploid spores that can continue to mate (conjugate) and reform the diploid. The haploid fission yeast Schizosaccharomyces pombe is a facultative sexual microorganism that can undergo mating when a nutrient deficiency is present. Exposure of S. pombe to hydrogen peroxide, an oxidative stress agent leading to oxidative DNA damage, induces mating and meiotic spore formation. The budding yeast Saccharomyces cerevisiae reproduces by mitosis as diploid cells when nutrients are abundant, but when starved, these yeasts undergo meiosis to form haploid spores. Haploid cells can then reproduce asexually through mitosis. Katz Ezov et al. presented evidence that natural populations of S. cerevisiae are dominated by clonal reproduction and self-pollination (in the form of intragroup mating). In nature, mating of haploid cells to form diploid cells most often occurs between members of the same clonal population, and outcrossing (crossing individuals of different lines) is rare. Analysis of the origin of natural strains of S. cerevisiae has led to the conclusion that outcrossing occurs only about once every 50,000 cell divisions. These observations indicate that the possible long-term benefits of outcrossing (eg, diversity creation) are likely to be insufficient to maintain sex as a whole from one generation to the next. Rather, short-term benefits, such as recombinational repair during meiosis, may be the key to maintaining sex in S. cerevisiae. Some Pucciniomycete yeasts, notably Sporidiobolus and Sporobolomyces species, produce aerospreadable, asexual ballistoconidia.

Usage

The beneficial physiological properties of yeast have led to their use in the field of biotechnology. The fermentation of sugars by yeast is the oldest and most common application of this technology. Many types of yeast are used in the production of many products: baker's yeast in the production of bread, brewer's yeast in the fermentation of beer, as well as yeast used in the fermentation of wine and in the production of xylitol. The so-called red rice yeast is actually a mold, Monascus purpureus. Yeasts include some of the most widely used model organisms for genetics and cell biology.

Alcoholic drinks

Wine

Yeast is used in winemaking when it converts the sugars (glucose and fructose) in grape juice (must) into ethanol. Yeast is usually already present in grape skins. Fermentation can be done with these endogenous "wild yeasts", but this procedure produces unpredictable results depending on the specific yeast species present. For this reason, a pure yeast culture is usually added to the wort; these yeasts rapidly dominate the fermentation. Wild yeasts are suppressed, which ensures a reliable and predictable fermentation. Most added wine yeasts are strains of S. cerevisiae, although not all species strains are suitable for this purpose. Different strains of the yeast S. cerevisiae have different physiological and enzymatic properties, so the actual isolation of the yeast can have a direct effect on the finished wine. Significant research has been undertaken to develop new grape yeast strains that produce atypical flavor profiles or increased complexity in wines. The growth of certain yeasts, such as Zygosaccharomyces and Brettanomyces, in wine can lead to wine defects and subsequent spoilage. Brettanomyces produces a host of metabolites when grown in wine, some of which are volatile phenolic compounds. Together, these compounds are often referred to as the "Brettanomyces character" and are often described as "antiseptic" or "fragrant" types. Brettanomyces are an important source of wine defects in the wine industry. Researchers at the University of British Columbia, Canada, have discovered a new strain of yeast that has a reduced amount of amines. The amines in red wine and Chardonnay produce off-flavours and cause headaches and hypertension in some people. About 30% of people are sensitive to biogenic amines such as histamine.

Bakery

Yeast, the most common of which is S. cerevisiae, is used in baking as a leavening agent, where it converts the edible/fermentable sugars present in the dough into carbon dioxide gas. This causes the dough to expand or rise as the gas creates bubbles. As the dough bakes, the yeast dies and the air bubbles "set in", giving the baked product a soft and spongy texture. The use of potatoes, potato boil water, eggs or sugar in bread dough accelerates the growth of yeast. Most of the yeasts used in baking are of the same type, common in alcoholic fermentation. In addition, Saccharomyces exiguus (also known as S. minor), a wild yeast found in plants, fruits, and grains, is sometimes used in baking. In breadmaking, yeast initially respires aerobically, producing carbon dioxide and water. With a lack of oxygen, fermentation begins, as a by-product of which ethanol is formed; however, it evaporates during baking. The first records that indicate this usage were from Ancient Egypt. The researchers believe that the mixture of flour and water was left out in the air on a warm day longer than usual, and the yeast, which is found in the flour's natural contaminants, caused the dough to "ferment" before baking. The resulting bread was lighter and tastier than a regular flat hard pie. There are several baker's yeast retailers today; one of the earliest businesses producing yeast in North America is Fleischmann's Yeast (Fleischmann's yeast), which began production in 1868. During World War II, Fleischmann developed granular active dry yeast that did not require refrigeration, had a longer shelf life than fresh yeast and grew twice as fast Baker's yeast is also sold as fresh yeast pressed into a square "cake" This form dies quickly so should be used shortly after production A dilute solution of water and sugar can be used to determine If the yeast has expired In solution, the active yeast will froth and bubble as the sugar is converted to ethanol and carbon dioxide Some recipes refer to this method as proof of yeast viability, as it "proves" (tests) the viability of the yeast before adding other ingredients.When using a sourdough starter, flour and water are added instead of sugar; this is called sourdough proof. When yeast is used to make bread, it is mixed with flour, salt, warm water or milk. The dough is kneaded until soft and then left to rise, sometimes until it doubles in size. The dough is then formed into loaves. In the manufacture of some baked goods, the dough is kneaded again after one rise and left to rise again (this is called checking the dough) and then baked into a product. A longer rise time gives better flavor, but the yeast may not raise the bread in the final stages if left for too long.

Biomedicine

Some yeasts may have potential applications in the field of biomedicine. One such yeast species, Yarrowia lipolytica, is known to decompose palm oil waste, TNT (explosive material) and other hydrocarbons such as alkanes, fatty acids, fats and oils. It can also tolerate high concentrations of salt and heavy metals and is being researched for its potential as a heavy metal biosorbent. Saccharomyces cerevisiae has the potential to bioremediate toxic pollutants such as arsenic from industrial effluents. Bronze statues are known to be destroyed by certain types of yeast. Various yeasts from Brazilian gold mines bioaccumulate free and complex silver ions.

Industrial production of ethanol

The ability of yeast to convert sugar into ethanol has been exploited in the biotech industry to produce ethanol fuel. The process begins with the grinding of feedstocks such as sugar cane, corn, or other grains, followed by the addition of dilute sulfuric acid or fungal alpha-amylase enzymes to break down starches into complex sugars. Glucoamylase is then added to break down the complex sugars into simple sugars. Yeast is then added to convert the simple sugars to ethanol, which is then distilled off to give ethanol up to 96% pure. The yeast Saccharomyces has been genetically modified to ferment xylose, one of the main fermentable sugars found in cellulosic biomasses such as agricultural residues, paper waste and wood chips. This development means that ethanol can be efficiently produced from cheaper feedstocks, making ethanol-based cellulosic fuel a more competitive alternative to gasoline fuels.

Soft drinks

Some sweet sodas can be made in the same way as beer, except that the fermentation then stops earlier, producing carbon dioxide and only trace amounts of alcohol, leaving a significant amount of residual sugar in the drink. A root beer originally made by American Indians, commercialized in the United States by Charles Elmer Hires and made especially popular during Prohibition. Kvass, a fermented rye drink popular in Eastern Europe. It has low alcohol content. Kombucha, fermented sweetened tea. In its preparation, yeast is used in symbiosis with acetic acid bacteria. The yeast species found in this tea can vary and may include Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii, and Zygosaccharomyces bailii. Also popular in Eastern Europe and some former Soviet republics is the so-called kombucha. Kefir and koumiss are produced by fermenting milk with yeast and bacteria. Mauby (Spanish: mabí), made by fermenting sugar with wild yeast naturally present in the bark of the Colubrina eelliptica tree, is a drink popular in the Caribbean.

Nutritional supplements

Probiotics

Some probiotic supplements contain the yeast S. boulardii to help maintain and restore the natural flora in the gastrointestinal tract. S. boulardii has been shown to reduce the symptoms of acute diarrhea, reduce the chance of infection with Clostridium difficile (often identified simply as C. difficile or C. diff), decrease intestinal motility in irritable bowel syndrome with diarrhea, and decrease the incidence of antibiotic-associated diarrhea. travel and HIV/AIDS.

aquarium hobby

Yeast is often used by aquarium hobbyists to produce carbon dioxide (CO2) to feed plants in aquariums. CO2 levels from yeast are more difficult to control than those generated by pressurized CO2 systems. However, the low cost of yeast makes it a widely used alternative.

Scientific research

Several yeast species, in particular S. cerevisiae, are widely used in genetics and cell biology, mainly because S. cerevisiae is a simple eukaryotic cell that serves as a model for all eukaryotes, including humans, to study fundamental cellular processes such as like how the cell cycle, DNA replication, recombination, cell division and metabolism. In addition, the yeast is easily manipulated and cultivated in the laboratory, which has enabled the development of powerful standardization methods such as yeast two-hybrid analysis, synthetic genetic analysis, and tetrad analysis. Many proteins important in human biology were first discovered by studying their homologues in yeast; these proteins include cell cycle proteins, signaling proteins, and protein processing enzymes. On April 24, 1996, S. cerevisiae was announced to be the first eukaryote to have its genome of 12 million base pairs fully sequenced as part of the Genome Project. At the time, it was the most complex organism to have a complete genome, developed over seven years with over 100 laboratories involved. The second yeast species in which the genome was isolated is Schizosaccharomyces pombe, the study of which was completed in 2002. It was the sixth eukaryotic genome, consisting of 13.8 million base pairs. As of 2014, over 50 yeast species have had their genomes sequenced and published.

Genetically Engineered Biofactors

Various types of yeast have been genetically engineered to produce various drugs efficiently, a technique called metabolic engineering. S. cerevisiae is easily genetically programmed; its physiology, metabolism and genetics are well known and suitable for use in harsh industrial environments. A variety of chemicals in different classes can be produced by genetically engineered yeast, including phenols, isoprenoids, alkaloids, and polyketides. About 20% of biopharmaceuticals are produced in S. cerevisiae, including insulin, hepatitis vaccines, and human serum albumin.

pathogenic yeast

Some types of yeast are opportunistic pathogens that can cause infection in people with compromised immune systems. Cryptococcus neoformans and Cryptococcus gattii are significant pathogens in immunocompromised people. These are the species that are primarily responsible for cryptococcosis, a fungal disease that occurs in approximately one million HIV/AIDS patients, causing more than 600,000 deaths each year. The cells of these yeasts are surrounded by a tough polysaccharide capsule that helps prevent them from being recognized and taken up by white blood cells in the human body. Yeasts of the genus Candida, another group of opportunistic pathogens, cause oral and vaginal infections in humans, known as candidiasis. Candida is commonly found as a symbiotic yeast in the mucous membranes of humans and other warm-blooded animals. However, sometimes these same strains can become pathogenic. Yeast cells grow a hyphal process that penetrates locally into the mucous membrane, causing irritation and desquamation of tissues. The pathogenic yeasts of candidiasis in the likely descending order of virulence for humans are: C. albicans, C. tropicalis, C. stellatoidea, C. glabrata, C. krusei, C. parapsilosis, C. guilliermondii, C. viswanathii, C. lusitaniae, and Rhodotorula mucilaginosa. Candida glabrata is the second most common Candida pathogen after C. albicans, causing urinary tract and bloodstream infections (candidaemia).

food contamination

Yeasts can grow in low pH foods (5.0 or lower) and in the presence of sugars, organic acids, and other easily digestible carbon sources. During growth, the yeast metabolizes some food components and produces metabolic end products. This leads to a change in the physical, chemical and sensory properties of the food, as well as spoilage of the food. Yeast growth in foods is often observed on their surface, as in cheeses or meats, or by the fermentation of sugars in beverages such as juices and semi-liquid products such as syrups and jams. Yeasts of the genus Zygosaccharomyces have a long history of use as a contaminant yeast in the food industry. This is mainly because these species can grow in the presence of high concentrations of sucrose, ethanol, acetic acid, sorbic acid, benzoic acid, and sulfur dioxide, some of the commonly used food preservation methods. Methylene blue is used to check for live yeast cells. In oenology, the main spoilage yeast is Brettanomyces bruxellensis.

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List of used literature:

Hoffman CS, Wood V, Fantes PA (October 2015). "An Ancient Yeast for Young Geneticists: A Primer on the Schizosaccharomyces pombe Model System." genetics. 201(2): 403–23. PMC 4596657 Freely accessible. PMID 26447128. doi:10.1534/genetics.115.181503

Kurtzman CP, Fell JW (2005). in: The Yeast Handbook, Gábor P, de la Rosa CL, eds. Biodiversity and Ecophysiology of Yeasts. Berlin: Springer. pp. 11-30. ISBN 978-3-540-26100-1

Ostergaard S, Olsson L, Nielsen J (2000). "Metabolic Engineering of Saccharomyces cerevisiae". Microbiology and Molecular Biology Reviews. 64(1): 34–50. PMC 98985 Freely accessible. PMID 10704473. doi:10.1128/MMBR.64.1.34-50.2000

Which have lost their mycelial structure, because their habitats have become substrates of liquid or semi-liquid consistency, containing a large amount of organic matter. The group of yeast fungi includes 1500 species that belong to the classes of Basidiomycetes and Ascomycetes.

In nature, yeasts are widely distributed and live on substrates rich in sugars, feeding on flower nectar, plant sap, dead phytomass, etc. Yeast fungi can live in soil and water, in the intestines of animals.

Yeasts are fungi that live during all or most of their life cycle in the form of individual single cells. Yeast cells are on average 3 to 7 microns in diameter, but there are some species whose cells can reach 40 microns. Yeast cells are immobile and oval in shape. Although yeast does not form mycelium, they have all the signs and properties of fungi. Yeast fungi are organotrophic eukaryotes with absorptive nutrition. These fungi use organic matter to obtain carbon and the energy necessary for life. Yeast needs oxygen for respiration, but in the absence of its access, many types of facultative anaerobes of yeast fungi obtain energy as a result of fermentation with the formation of alcohols. Yeast fermentation stops or stops completely if oxygen begins to flow to the fermented substrate, since respiration is a more efficient process for obtaining energy. But if the concentration of sugars in the nutrient medium is very high, then even with the access of oxygen, the processes of respiration and fermentation are carried out simultaneously. Yeast fungi are very demanding on nutritional conditions. In an anaerobic environment, yeast assimilate only glucose, while in an aerobic environment they can also use hydrocarbons, fats, aromatic compounds, organic acids, and alcohols as energy sources.

The growth and reproduction of yeast occurs at a tremendous speed, while provoking characteristic changes in the environment. So, thanks to the process of alcoholic fermentation, yeast has become widespread throughout the world. Yeast is believed to be the oldest of the plants cultivated by man. Reproduction of yeast is carried out by budding (division). Sexual reproduction is also possible. In this case, the resulting zygote is transformed into a "bag" in which 4-8 spores are enclosed. In the unicellular state, yeasts are capable of vegetative reproduction. So, spores or zygotes can bud. The division of yeast into groups (classes Ascomycetes or Basidiomycetes) is based on the methods of their sexual reproduction. There are types of yeast that do not have sexual reproduction. Their scientists included in the class of imperfect fungi (Fungi Imperfecti, or Deuteromycetes).

Certain types of yeast have been used by man since ancient times in the manufacture of wine, beer, bread, kvass, in the industrial production of alcohol, etc. Some types of yeast are used in biotechnology due to their important physiological features. In modern production, using yeast, food additives, enzymes, xylitol are obtained, water is purified from oil pollution. But there are also negative properties of yeast. Some types of yeast can cause disease in humans, as they are facultative or opportunistic pathogens. Such diseases include candidiasis, cryptococcosis, pitiriasis.