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Yeasts are , single-celled classified as members of the kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 are currently recognized. Molecular Mechanisms in Yeast Carbon Metabolism. The second completely sequenced yeast genome came 6 years later from the fission yeast Schizosaccharomyces pombe, which diverged from S. cerevisiae probably more than 300 million years ago. They are estimated to constitute 1% of all described fungal species.

Yeasts are unicellular organisms that evolved from multicellular ancestors, with some species having the ability to develop multicellular characteristics by forming strings of connected budding cells known as or false hyphae. Yeast sizes vary greatly, depending on species and environment, typically measuring 3–4  in , although some yeasts can grow to 40 µm in size. Most yeasts reproduce asexually by , and many do so by the asymmetric division process known as . With their single-celled growth habit, yeasts can be contrasted with molds, which grow . Fungal species that can take both forms (depending on temperature or other conditions) are called .

The yeast species Saccharomyces cerevisiae converts to and in a process known as fermentation. The products of this reaction have been used in and the production of alcoholic beverages for thousands of years. S. cerevisiae is also an important in modern research, and is one of the most thoroughly studied microorganisms. Researchers have cultured it in order to understand the biology of the eukaryotic cell and ultimately human biology in great detail. Other species of yeasts, such as , are opportunistic pathogens and can cause in humans. Yeasts have recently been used to generate electricity in microbial fuel cells and to produce for the industry.

Yeasts do not form a single taxonomic or grouping. The term "yeast" is often taken as a for Saccharomyces cerevisiae, but the phylogenetic diversity of yeasts is shown by their placement in two separate : the and the . The budding yeasts or "true yeasts" are classified in the order Saccharomycetales, within the phylum Ascomycota.


History
The word "yeast" comes from Old English gist, gyst, and from the Indo-European root yes-, meaning "boil", "foam", or "bubble". Https://mbio.asm.org/content/10/2/e00388-19/article-info>< /ref> In 1680, Dutch naturalist Anton van Leeuwenhoek first observed yeast, but at the time did not consider them to be , but rather globular structures as researchers were doubtful whether yeasts were algae or fungi. recognized them as fungi in 1837.

In 1857, French microbiologist showed that by bubbling oxygen into the yeast broth, could be increased, but fermentation was inhibited – an observation later called the "". In the paper " Mémoire sur la fermentation alcoolique," Pasteur proved that alcoholic fermentation was conducted by living yeasts and not by a chemical catalyst.

By the late 18th century two yeast strains used in brewing had been identified: Saccharomyces cerevisiae (top-fermenting yeast) and S. carlsbergensis (bottom-fermenting yeast). S. cerevisiae has been sold commercially by the Dutch for bread-making since 1780; while, around 1800, the Germans started producing S. cerevisiae in the form of cream. In 1825, a method was developed to remove the liquid so the yeast could be prepared as solid blocks. The industrial production of yeast blocks was enhanced by the introduction of the 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, naturally occurring airborne yeasts were used almost exclusively until commercial yeast was marketed at the Centennial Exposition in 1876 in Philadelphia, where Charles L. Fleischmann exhibited the product and a process to use it, as well as serving the resultant baked bread.

The (first patented in the 1850s in Europe) liberated and from seasonal constraints for the first time and allowed them to exit cellars and other earthen environments. For , who made his livelihood in prior to the development of the fridge, the brewing season lasted from September through to May. The same seasonal restrictions formerly governed the 's art.


Nutrition and growth
Yeasts are , as they use as a source of energy and do not require sunlight to grow. Carbon is obtained mostly from sugars, such as and , or disaccharides such as and . Some species can metabolize sugars such as ribose, alcohols, and . Yeast species either require oxygen for aerobic cellular respiration () or are anaerobic, but also have aerobic methods of energy production (facultative anaerobes). Unlike , no known yeast species grow only anaerobically (obligate anaerobes). Most yeasts grow best in a neutral or slightly acidic pH environment.

Yeasts vary in regard to the temperature range in which they grow best. For example, Leucosporidium frigidum grows at , Saccharomyces telluris at , and at . The cells can survive freezing under certain conditions, with viability decreasing over time.

In general, yeasts are grown in the laboratory on solid or in liquid . Common media used for the cultivation of yeasts include potato dextrose agar or potato dextrose broth, Wallerstein Laboratories nutrient , yeast agar, and yeast mould agar or broth. Home brewers who cultivate yeast frequently use dried and agar as a solid growth medium. The is sometimes added to yeast growth media to inhibit the growth of yeasts and select for wild/indigenous yeast species. This will change the yeast process.

The appearance of a white, thready yeast, commonly known as kahm yeast, is often a byproduct of the lactofermentation (or pickling) of certain vegetables. It is usually the result of exposure to air. Although harmless, it can give pickled vegetables a bad flavor and must be removed regularly during fermentation.


Ecology
Yeasts are very common in the environment, and are often isolated from sugar-rich materials. Examples include naturally occurring yeasts on the skins of fruits and berries (such as grapes, apples, or ), and exudates from plants (such as plant saps or cacti). Some yeasts are found in association with soil and insects. The ecological function and of yeasts are relatively unknown compared to those of other . Yeasts, including , rubra, and Trichosporon cutaneum, have been found living in between people's toes as part of their . Yeasts are also present in the of mammals and some insects and even deep-sea environments host an array of yeasts.

An Indian study of seven species and nine plant species found 45 species from 16 genera colonize the of flowers and honey stomachs of bees. Most were members of the genus Candida; the most common species in honey stomachs was Dekkera intermedia and in flower nectaries, . Yeast colonising nectaries of the stinking hellebore have been found to raise the temperature of the flower, which may aid in attracting pollinators by increasing the evaporation of volatile organic compounds. A has been recorded as a partner in a complex relationship between , their mutualistic fungus, a fungal of the fungus and a bacterium that kills the parasite. The yeast has a negative effect on the bacteria that normally produce antibiotics to kill the parasite, so may affect the ants' health by allowing the parasite to spread.

Certain strains of some species of yeasts produce proteins called yeast killer toxins that allow them to eliminate competing strains. (See main article on .) This can cause problems for winemaking but could potentially also be used to advantage by using killer toxin-producing strains to make the wine. Yeast killer toxins may also have medical applications in treating yeast infections (see "Pathogenic yeasts" section below).

Marine yeasts, defined as the yeasts that are isolated from marine environments, are able to grow better on a medium prepared using seawater rather than freshwater. The first marine yeasts were isolated by Bernhard Fischer in 1894 from the Atlantic Ocean, and those were identified as Torula sp. and Mycoderma sp. Following this discovery, various other marine yeasts have been isolated from around the world from different sources, including seawater, seaweeds, marine fish and mammals. Among these isolates, some marine yeasts originated from terrestrial habitats (grouped as facultative marine yeast), which were brought to and survived in marine environments. The other marine yeasts were grouped as obligate or indigenous marine yeasts, which confine to marine habitats. However, no sufficient evidence has been found to explain the indispensability of seawater for obligate marine yeasts. This article contains quotations from this source, which is available under a Creative Commons Attribution license. It has been reported that marine yeasts are able to produce many bioactive substances, such as amino acids, glucans, glutathione, toxins, enzymes, phytase, and vitamins with potential applications in the food, pharmaceutical, cosmetic, and chemical industries as well as for marine culture and environmental protection. Marine yeast was successfully used to produce bioethanol using seawater-based media which will potentially reduce the of bioethanol.


Reproduction
Yeasts, like all fungi, may have asexual and sexual reproductive cycles. The most common mode of vegetative growth in yeast is asexual reproduction by , where a small bud (also known as a bleb or daughter cell) is formed on the parent cell. The of the parent cell splits into a daughter nucleus and migrates into the daughter cell. The bud then continues to grow until it separates from the parent cell, forming a new cell. The daughter cell produced during the budding process is generally smaller than the mother cell. Some yeasts, including Schizosaccharomyces pombe, reproduce by fission instead of budding, and thereby creating two identically sized daughter cells.

In general, under high-stress conditions such as starvation, cells will die; under the same conditions, however, cells can undergo sporulation, entering sexual reproduction () and producing a variety of haploid , which can go on to mate (conjugate), reforming the diploid.

The haploid fission yeast Schizosaccharomyces pombe is a sexual microorganism that can undergo mating when nutrients are limiting. Exposure of S. pombe to hydrogen peroxide, an agent that causes oxidative stress leading to oxidative DNA damage, strongly induces mating and the formation of meiotic spores. The budding yeast Saccharomyces cerevisiae reproduces by mitosis as diploid cells when nutrients are abundant, but when starved, this yeast undergoes meiosis to form haploid spores. Haploid cells may then reproduce asexually by mitosis. Katz Ezov et al. presented evidence that in natural S. cerevisiae populations clonal reproduction and selfing (in the form of intratetrad mating) predominate. In nature, mating of haploid cells to form diploid cells is most often between members of the same clonal population and is uncommon. Analysis of the ancestry of natural S. cerevisiae strains led to the conclusion that out-crossing occurs only about once every 50,000 cell divisions. These observations suggest that the possible long-term benefits of outcrossing (e.g. generation of diversity) are likely to be insufficient for generally maintaining sex from one generation to the next. Rather, a short-term benefit, such as recombinational repair during meiosis,

(2021). 9780306472619, Springer.
may be the key to the maintenance of sex in S. cerevisiae.

Some yeasts, in particular species of and , produce aerially dispersed, asexual .


Uses
The useful physiological properties of yeast have led to their use in the field of . Fermentation of sugars by yeast is the oldest and largest application of this technology. Many types of yeasts are used for making many foods: baker's yeast in bread production, brewer's yeast in beer fermentation, and yeast in wine fermentation and for production. So-called red rice yeast is actually a mold, Monascus purpureus. Yeasts include some of the most widely used for and .


Alcoholic beverages
Alcoholic beverages are defined as that contain (C2H5OH). This ethanol is almost always produced by fermentation – the of by certain species of yeasts under anaerobic or low-oxygen conditions. Beverages such as mead, wine, beer, or distilled spirits all use yeast at some stage of their production. A distilled beverage is a beverage containing ethanol that has been purified by . Carbohydrate-containing plant material is fermented by yeast, producing a dilute solution of ethanol in the process. Spirits such as and are prepared by distilling these dilute solutions of ethanol. Components other than ethanol are collected in the condensate, including water, , and other alcohols, which (in addition to that provided by the oak in which it may be aged) account for the of the beverage.


Beer
Brewing yeasts may be classed as "top-cropping" (or "top-fermenting") and "bottom-cropping" (or "bottom-fermenting").
(2021). 9781420015171, CRC Press. .
Top-cropping yeasts are so called because they form a foam at the top of the during fermentation. An example of a top-cropping yeast is Saccharomyces cerevisiae, sometimes called an "ale yeast". Bottom-cropping yeasts are typically used to produce -type beers, though they can also produce -type beers. These yeasts ferment well at low temperatures. An example of bottom-cropping yeast is Saccharomyces pastorianus, formerly known as S. carlsbergensis.

Decades ago, taxonomists reclassified S. carlsbergensis (uvarum) as a member of S. cerevisiae, noting that the only distinct difference between the two is metabolic. Lager strains of S. cerevisiae secrete an enzyme called melibiase, allowing them to hydrolyse , a , into more fermentable . Top- and bottom-cropping and cold- and warm-fermenting distinctions are largely generalizations used by laypersons to communicate to the general public.For more on the taxonomical differences, see

The most common top-cropping brewer's yeast, S. cerevisiae, is the same species as the common baking yeast. Brewer's yeast is also very rich in essential minerals and the (except B12). However, baking and brewing yeasts typically belong to different strains, cultivated to favour different characteristics: baking yeast strains are more aggressive, to carbonate in the shortest amount of time possible; brewing yeast strains act more slowly but tend to produce fewer off-flavours and tolerate higher alcohol concentrations (with some strains, up to 22%).

Dekkera/Brettanomyces is a genus of yeast known for its important role in the production of '' and specialty , along with the secondary conditioning of a particular Belgian . The taxonomy of the genus Brettanomyces has been debated since its early discovery and has seen many reclassifications over the years. Early classification was based on a few species that reproduced asexually (anamorph form) through multipolar budding. Shortly after, the formation of ascospores was observed and the genus Dekkera, which reproduces sexually (teleomorph form), was introduced as part of the taxonomy. The current taxonomy includes five species within the genera of Dekkera/Brettanomyces. Those are the anamorphs Brettanomyces bruxellensis, Brettanomyces anomalus, Brettanomyces custersianus, Brettanomyces naardenensis, and Brettanomyces nanus, with teleomorphs existing for the first two species, Dekkera bruxellensis and . The distinction between Dekkera and Brettanomyces is arguable, with Oelofse et al. (2008) citing Loureiro and Malfeito-Ferreira from 2006 when they affirmed that current molecular DNA detection techniques have uncovered no variance between the anamorph and teleomorph states. Over the past decade, Brettanomyces spp. have seen an increasing use in the craft-brewing sector of the industry, with a handful of breweries having produced beers that were primarily fermented with pure cultures of Brettanomyces spp. This has occurred out of experimentation, as very little information exists regarding pure culture fermentative capabilities and the aromatic compounds produced by various strains. Dekkera/ Brettanomyces spp. have been the subjects of numerous studies conducted over the past century, although a majority of the recent research has focused on enhancing the knowledge of the wine industry. Recent research on eight Brettanomyces strains available in the brewing industry focused on strain-specific fermentations and identified the major compounds produced during pure culture anaerobic fermentation in wort.


Wine
Yeast is used in , where it converts the sugars present ( and ) in () into ethanol. Yeast is normally already present on grape skins. Fermentation can be done with this endogenous "wild yeast", but this procedure gives unpredictable results, which depend upon the exact types of yeast species present. For this reason, a pure yeast culture is usually added to the must; this yeast quickly dominates the fermentation. The wild yeasts are repressed, which ensures a reliable and predictable fermentation.

Most added wine yeasts are strains of S. cerevisiae, though not all strains of the species are suitable. Different S. cerevisiae yeast strains have differing physiological and fermentative properties, therefore the actual strain of yeast selected can have a direct impact on the finished wine. Significant research has been undertaken into the development of novel wine yeast strains that produce atypical flavour profiles or increased complexity in wines.

The growth of some yeasts, such as Zygosaccharomyces and , in wine can result in and subsequent spoilage. Brettanomyces produces an array of when growing in wine, some of which are volatile compounds. Together, these compounds are often referred to as " Brettanomyces character", and are often described as "" or "barnyard" type aromas. Brettanomyces is a significant contributor to wine faults within the wine industry.

Researchers from the University of British Columbia, Canada, have found a new strain of yeast that has reduced . The amines in and produce off-flavors and cause headaches and hypertension in some people. About 30% of people are sensitive to biogenic amines, such as .


Baking
Yeast, the most common one being S. cerevisiae, is used in baking as a , where it converts the food/fermentable sugars present in dough into the gas . This causes the dough to expand or rise as gas forms pockets or bubbles. When the dough is baked, the yeast dies and the air pockets "set", giving the baked product a soft and spongy texture. The use of potatoes, water from potato boiling, eggs, or sugar in a bread dough accelerates the growth of yeasts. Most yeasts used in baking are of the same species common in alcoholic fermentation. In addition, Saccharomyces exiguus (also known as S. minor), a wild yeast found on plants, fruits, and grains, is occasionally used for baking. In breadmaking, the yeast initially respires aerobically, producing carbon dioxide and water. When the oxygen is depleted, fermentation begins, producing ethanol as a waste product; however, this evaporates during baking.

It is not known when yeast was first used to bake bread. The first records that show this use came from . Researchers speculate a mixture of flour meal and water was left longer than usual on a warm day and the yeasts that occur in natural contaminants of the caused it to ferment before baking. The resulting bread would have been lighter and tastier than the normal flat, hard cake.

Today, there are several retailers of baker's yeast; one of the earlier developments in North America is Fleischmann's Yeast, in 1868. During World War II, Fleischmann's developed a active dry yeast which did not require refrigeration, had a longer than fresh yeast, and rose twice as fast. Baker's yeast is also sold as a fresh yeast compressed into a square "cake". This form perishes quickly, so must be used soon after production. A weak solution of water and sugar can be used to determine whether yeast is expired. In the solution, active yeast will foam and bubble as it ferments the sugar into ethanol and carbon dioxide. Some recipes refer to this as proofing the yeast, as it "proves" (tests) the viability of the yeast before the other ingredients are added. When a starter is used, flour and water are added instead of sugar; this is referred to as proofing the sponge.

When yeast is used for making bread, it is mixed with , salt, and warm water or milk. The dough is until it is smooth, and then left to rise, sometimes until it has doubled in size. The dough is then shaped into loaves. Some bread doughs are knocked back after one rising and left to rise again (this is called dough proofing) and then baked. A longer rising time gives a better flavor, but the yeast can fail to raise the bread in the final stages if it is left for too long initially.


Bioremediation
Some yeasts can find potential application in the field of . One such yeast, Yarrowia lipolytica, is known to degrade mill , (an explosive material), and other , such as , , fats and oils. It can also tolerate high concentrations of salt and heavy metals, and is being investigated for its potential as a heavy metal . Saccharomyces cerevisiae has potential to bioremediate toxic pollutants like from industrial effluent. Bronze statues are known to be degraded by certain species of yeast. Different yeasts from Brazilian gold mines free and complexed silver ions.


Industrial ethanol production
The ability of yeast to convert sugar into ethanol has been harnessed by the biotechnology industry to produce . The process starts by milling a feedstock, such as , , or other , and then adding dilute , or fungal alpha enzymes, to break down the starches into complex sugars. A glucoamylase is then added to break the complex sugars down into simple sugars. After this, yeasts are added to convert the simple sugars to ethanol, which is then distilled off to obtain ethanol up to 96% in purity.

Saccharomyces yeasts have been genetically engineered to ferment , one of the major fermentable sugars present in cellulosic biomasses, such as agriculture residues, paper wastes, and wood chips. Such a development means ethanol can be efficiently produced from more inexpensive feedstocks, making cellulosic ethanol fuel a more competitively priced alternative to gasoline fuels.


Nonalcoholic beverages
A number of sweet can be produced by the same methods as beer, except the fermentation is stopped sooner, producing carbon dioxide, but only trace amounts of alcohol, leaving a significant amount of residual sugar in the drink.
  • , originally made by Native Americans, commercialized in the United States by Charles Elmer Hires and especially popular during Prohibition
  • , a fermented drink made from , popular in Eastern Europe. It has a recognizable, but low alcoholic content.
  • , a fermented sweetened tea. Yeast in with acetic acid bacteria is used in its preparation. Species of yeasts found in the tea can vary, and may include: Brettanomyces bruxellensis, , Schizosaccharomyces pombe, Torulaspora delbrueckii and Zygosaccharomyces bailii. Also popular in Eastern Europe and some former Soviet republics under the name chajnyj grib (Чайный гриб), which means "tea mushroom".
  • and are made by fermenting milk with yeast and bacteria.
  • (mabí), made by fermenting sugar with the wild yeasts naturally present on the bark of the Colubrina elliptica tree, popular in the


Nutritional supplements
Yeast is used in nutritional supplements, especially those marketed to . It is often referred to as "nutritional yeast" when sold as a dietary supplement. Nutritional yeast is a deactivated yeast, usually S. cerevisiae. It is naturally low in fat and and a source of protein and vitamins, especially most vitamins (though it does not contain much vitamin B12 without fortification), as well as other minerals and cofactors required for growth. Some brands of nutritional yeast, though not all, are fortified with , which is produced separately by .

In 1920, the Fleischmann Yeast Company began to promote yeast cakes in a "Yeast for Health" campaign. They initially emphasized yeast as a source of vitamins, good for skin and digestion. Their later advertising claimed a much broader range of health benefits, and was censured as misleading by the Federal Trade Commission. The for yeast cakes lasted until the late 1930s.

Nutritional yeast has a nutty, cheesy flavor and is often used as an ingredient in cheese substitutes. Another popular use is as a topping for popcorn. It can also be used in mashed and fried potatoes, as well as in . It comes in the form of flakes, or as a yellow powder similar in texture to . In Australia, it is sometimes sold as "savoury yeast flakes". Though "nutritional yeast" usually refers to commercial products, inadequately fed prisoners have used "home-grown" yeast to prevent vitamin deficiency.


Probiotics
Some supplements use the yeast S. boulardii to maintain and restore the natural flora in the gastrointestinal tract. S. boulardii has been shown to reduce the symptoms of acute , reduce the chance of infection by Clostridium difficile (often identified simply as C. difficile or C. diff), reduce bowel movements in diarrhea-predominant IBS patients, and reduce the incidence of antibiotic-, traveler's-, and HIV/AIDS-associated diarrheas.


Aquarium hobby
Yeast is often used by hobbyists to generate carbon dioxide (CO2) to nourish plants in . CO2 levels from yeast are more difficult to regulate than those from pressurized CO2 systems. However, the low cost of yeast makes it a widely used alternative.


Yeast extract
Yeast extract is the common name for various forms of processed yeast products that are used as or . They are often used in the same way that monosodium glutamate (MSG) is used and, like MSG, often contain free .Priest and Stewart (2006), p. 691. The general method for making yeast extract for food products such as and on a commercial scale is to add salt to a suspension of yeast, making the solution hypertonic, which leads to the cells' shrivelling up. This triggers autolysis, wherein the yeast's enzymes break their own down into simpler compounds, a process of self-destruction. The dying yeast cells are then heated to complete their breakdown, after which the husks (yeast with thick cell walls that would give poor texture) are separated. Yeast autolysates are used in and (Australia); (the United Kingdom); the unrelated Marmite (New Zealand); (Germany); and ().


Scientific research
Several yeasts, in particular S. cerevisiae and S. pombe, have been widely used in genetics and cell biology, largely because they are simple cells, serving as a model for all eukaryotes, including humans, for the study of fundamental cellular processes such as the , , recombination, , and metabolism. Also, yeasts are easily manipulated and cultured in the laboratory, which has allowed for the development of powerful standard techniques, such as , synthetic genetic array 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, , and protein-processing .

On 24 April 1996, S. cerevisiae was announced to be the first eukaryote to have its , consisting of 12 million , fully sequenced as part of the . At the time, it was the most complex organism to have its full genome sequenced, and the work seven years and the involvement of more than 100 laboratories to accomplish. The second yeast species to have its genome sequenced was Schizosaccharomyces pombe, which was completed in 2002. It was the sixth eukaryotic genome sequenced and consists of 13.8 million base pairs. As of 2014, over 50 yeast species have had their genomes sequenced and published.

Genomic and functional gene annotation of the two major yeast models can be accessed via their respective model organism databases: SGD and PomBase.


Genetically engineered biofactories
Various yeast species have been genetically engineered to efficiently produce various drugs, a technique called metabolic engineering. S. cerevisiae is easy to genetically engineer; its physiology, metabolism and genetics are well known, and it is amenable for use in harsh industrial conditions. A wide variety of chemical in different classes can be produced by engineered yeast, including , , , and . About 20% of biopharmaceuticals are produced in S. cerevisiae, including , for , and human serum albumin.


Pathogenic yeasts
Some species of yeast are opportunistic pathogens that can cause infection in people with compromised . Cryptococcus neoformans and Cryptococcus gattii are significant pathogens of immunocompromised people. They are the species primarily responsible for , a fungal disease that occurs in about one million HIV/AIDS patients, causing over 600,000 deaths annually. The cells of these yeast are surrounded by a rigid capsule, which helps to prevent them from being recognised and engulfed by white blood cells in the human body.

Yeasts of the genus Candida, another group of opportunistic pathogens, cause and vaginal infections in humans, known as . Candida is commonly found as a yeast in the of humans and other warm-blooded animals. However, sometimes these same strains can become pathogenic. The yeast cells sprout a outgrowth, which locally penetrates the , causing irritation and shedding of the tissues. A book from the 1980s listed the pathogenic yeasts of candidiasis in probable descending order of for humans as: , C. tropicalis, C. stellatoidea, , , C. parapsilosis, C. guilliermondii, C. viswanathii, C. lusitaniae, and . Candida glabrata is the second most common Candida pathogen after C. albicans, causing infections of the , and of the (). has been more recently identified.


Food spoilage
Yeasts are able to grow in foods with a low pH (5.0 or lower) and in the presence of sugars, organic acids, and other easily metabolized carbon sources. During their growth, yeasts metabolize some food components and produce metabolic end products. This causes the physical, chemical, and sensible properties of a food to change, and the food is spoiled. The growth of yeast within food products is often seen on their surfaces, as in cheeses or meats, or by the fermentation of sugars in beverages, such as juices, and semiliquid products, such as and . The yeast of the genus Zygosaccharomyces have had a long history as spoilage yeasts within the . This is mainly because these species can grow in the presence of high sucrose, ethanol, , , , and concentrations, representing some of the commonly used food preservation methods. is used to test for the presence of live yeast cells. In , the major spoilage yeast is Brettanomyces bruxellensis.

has been detected in and meat.

(2014). 9781118522677, . .


Symbiosis
An Indian study of seven species and 9 plant species found 45 yeast species from 16 genera colonise the of flowers and honey stomachs of bees. Most were members of the genus Candida; the most common species in honey bee stomachs was Dekkera intermedia, while the most common species colonising flower nectaries was . Although the mechanics are not fully understood, it was found that A. indica flowers more if is present.

In another example, Spathaspora passalidarum, found in the digestive tract of , aids the digestion of plant cells by fermenting .


See also
  • Ethanol fermentation
  • Evolution of aerobic fermentation
  • Kazachstania yasuniensis – a recently isolated yeast
  • (fungal infection in animals)
  • Plasmid#Yeast plasmids
  • Start point (yeast)
  • WHI3


Further reading


External links

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