Saccharomyces cerevisiae.Saccharomyces cerevisiae.Kübra kılıçKübra kılıç

Classification of saccharomyces cerevisiae

Scientific classification; Kingdom: fungi Phylum: ascomycota Subphylum: saccharomycotina Class: saccharomycetes Order: saccaromycetales Family: saccharomycetaceae Genus: saccharomyces Species: s.cerevisiae Binomial name; saccharomyces

cerevisiae

The history of s.cerevisiae

The first written records of brewing come from Sumeria about 6,000 years ago. But all that drinking was making people hungry, so in Egypt around 5,000 years ago, they starting making bread (or at least, wrote down the recipe). Before that, bread was tough, dry stuff that tended to break your teeth and made your jaw ache. Bread made with yeast was wonderful, light, tasty stuff. The secret? Saccharomyces cerevisiae: In the upper, left hand corner of this ancient seal you can see a representation of Sumarians drinking beer through straws

What is s.cerevisiae?What is s.cerevisiae?

Saccharomyces cerevisiaeSaccharomyces cerevisiae is a is a speciesspecies of of buddingbudding yeastyeast. It is . It is perhaps the most useful yeast owing to its use since ancient times perhaps the most useful yeast owing to its use since ancient times in in bakingbaking and and brewingbrewing. It is believed that it was originally isolated . It is believed that it was originally isolated from the skins of grapes (one can see the yeast as a component from the skins of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-colored fruits such of the thin white film on the skins of some dark-colored fruits such as plums; it exists among the as plums; it exists among the waxeswaxes of the of the cuticlecuticle). It is one of the ). It is one of the most intensively studied most intensively studied eukaryoticeukaryotic model model organismsorganisms in in molecularmolecular and and cellcell biologybiology, much like , much like EscherichiaEscherichia colicoli as the model as the model prokaryoteprokaryote. It is the microorganism behind the most common type . It is the microorganism behind the most common type of of fermentationfermentation. . Saccharomyces cerevisiaeSaccharomyces cerevisiae cells are round to cells are round to ovoid, 5–10 ovoid, 5–10 micrometresmicrometres in diameter. It reproduces by a division in diameter. It reproduces by a division process known as process known as buddingbudding

Video of s.cerevisiaeVideo of s.cerevisiae

Structure of s. cerevisiaeStructure of s. cerevisiae Saccharomyces cerevisiaeSaccharomyces cerevisiae is in is in

the fungi kingdom. The reasons the fungi kingdom. The reasons for this classification are because for this classification are because it has a cell wall made of chitin, it it has a cell wall made of chitin, it has no peptiodglycan in its cell has no peptiodglycan in its cell walls, and its lipids are ester walls, and its lipids are ester linked. It also uses DNA template linked. It also uses DNA template for protein synthesis and it has for protein synthesis and it has larger ribosomes. It is then larger ribosomes. It is then consider a yeast because it is a consider a yeast because it is a unicellular organism so it can not unicellular organism so it can not form a fruiting body; like other form a fruiting body; like other fungi.fungi.

Life cycle of s. cerevisiae

There are two forms in which yeast cells can survive and grow: haploid and diploid. The haploid cells undergo a simple lifecycle of mitosis and growth, and under conditions of high stress will generally simply die. The diploid cells (the preferential 'form' of yeast) similarly undergo a simple lifecycle of mitosis and growth, but under conditions of stress can undergo sporulation, entering meiosis and producing a variety of haploid spores, which can go on to mate

Nutritional requirements of Nutritional requirements of s.cerevisiaes.cerevisiae

Saccharomyces cerevisiaeSaccharomyces cerevisiae gets its energy from gets its energy from glucoseglucose

All All strainsstrains of of Saccharomyces cerevisiaeSaccharomyces cerevisiae can can grow grow aerobicallyaerobically on on glucoseglucose, , maltosemaltose, and , and trehalosetrehalose and fail to grow on and fail to grow on lactoselactose and and cellobiosecellobiose . .

It was shown that galactose and fructose were It was shown that galactose and fructose were two of the best fermenting sugars. The ability of two of the best fermenting sugars. The ability of yeasts to use different sugars can differ yeasts to use different sugars can differ depending on whether they are grown depending on whether they are grown aerobically or anaerobically. Some strains aerobically or anaerobically. Some strains cannot grow anaerobically on cannot grow anaerobically on sucrosesucrose and and trehalosetrehalose..

All strains can utilise All strains can utilise ammoniaammonia and and ureaurea as the sole as the sole nitrogennitrogen source, but cannot source, but cannot utilise utilise nitratenitrate since they lack the ability to since they lack the ability to reduce them to reduce them to ammoniumammonium ionsions. They . They can also utilise most can also utilise most amino amino acidsacids, small , small peptidespeptides and nitrogen bases as a nitrogen and nitrogen bases as a nitrogen source. source.

S. cerevisiaeS. cerevisiae does not excrete does not excrete proteasesproteases so extracellular protein cannot be so extracellular protein cannot be metabolized.metabolized.

Cell cycle of s. cerevisiaeCell cycle of s. cerevisiae

Growth in Growth in yeastyeast is synchronised with the is synchronised with the growth of the bud, which reaches the size growth of the bud, which reaches the size of the mature cell by the time it separates of the mature cell by the time it separates from the parent cell. from the parent cell.

In rapidly growing yeast In rapidly growing yeast culturescultures, all the , all the cells can be seen to have buds since bud cells can be seen to have buds since bud formation occupies the whole formation occupies the whole cellcell cyclecycle. . Both mother and daughter cell can initiate Both mother and daughter cell can initiate bud formation before cell separation has bud formation before cell separation has occurred occurred

. In yeast cultures which . In yeast cultures which are growing more slowly, are growing more slowly, cells lacking buds can be cells lacking buds can be seen and seen and budbud formationformation only occupies a part of only occupies a part of the cell cycle. The cell the cell cycle. The cell cycle in yeast normally cycle in yeast normally consists of the following consists of the following stages -- G1, S, G2 and stages -- G1, S, G2 and M -- which are the normal M -- which are the normal stages of stages of mitosismitosis..

Fermentation of yeastFermentation of yeast

Saccharomyces cerevisiaeSaccharomyces cerevisiae is commonly known as is commonly known as "bakers yeast" or "brewers yeast". The yeast "bakers yeast" or "brewers yeast". The yeast fermentsferments sugars present in the flour or added to the dough, sugars present in the flour or added to the dough, giving off giving off carbon dioxidecarbon dioxide (CO2) and (CO2) and alcoholalcohol (ethanol). The CO2 is trapped as tiny bubbles in the (ethanol). The CO2 is trapped as tiny bubbles in the dough, which rises.dough, which rises.

Why does yeast do this?Why does yeast do this?To gain energy from the breakdown (fermentation) of To gain energy from the breakdown (fermentation) of carbohydrates, as in the upper of diagram.carbohydrates, as in the upper of diagram.

Fermentation of sugar with Fermentation of sugar with SaccharomycesSaccharomyces proceeds according to proceeds according to the (unbalanced) chemical reaction: the (unbalanced) chemical reaction:

C6H12O6 + H2O ---> CO2 + C6H12O6 + H2O ---> CO2 + CH3CH2OH (or C2H5OH) CH3CH2OH (or C2H5OH)

or or sugar (glucose) plus water yields carbon sugar (glucose) plus water yields carbon

dioxide plus ethanol (ethyl alcohol) dioxide plus ethanol (ethyl alcohol)

İmportance of s. cerevisiae

• : Saccharomyces cerevisiae is one of the most important fungi in the history of the world. This yeast is responsible for the production of ethanol .

• and is the reasons your mother’s bread dough rises in the pan. That is where the names brewer’s and baker’s yeast come from

Yeast in biological research

• A model organism• When researchers look for an organism to use

in their studies, they look for several traits. Among these are size, generation time, accessibility, manipulation, genetics, conservation of mechanisms, and potential economic benefit.

• Saccharomyces cerevisiae has developed as a model organism because it scores favorably on a number of these criteria.

Where yeasts are usable?Where yeasts are usable?

İt is supplementation in growing İt is supplementation in growing animals in the dairy industry.animals in the dairy industry.

Yeast products have been added Yeast products have been added to the diets of monogastric as to the diets of monogastric as well as ruminant animals for well as ruminant animals for many years to improve their many years to improve their productivity with a variety of productivity with a variety of resultsresults

In the dairy industry, yeast has In the dairy industry, yeast has been used since the early 1900s been used since the early 1900s as an enhancer in milk as an enhancer in milk production and in growing production and in growing animals to improve their gains animals to improve their gains and efficiency. and efficiency.

Biotechnology And Yeast

Both yeast cells and human cells are eukaryotic—possessing a nucleus and membrane-bound organelles such as ribosomes and mitochondria.

Yeasts have been subjected to the alteration of their own genes, as biotechnologists attempt to develop strains of yeast more efficient in the metabolism of sugars for food and industrial applications.

In 1993 the first yeast chromosome was completely mapped, and the function of each of the 182 genes has yielded insight into such vital genetic processes as mutation repair, enzyme production, and cellular division regulation.

These findings may yield insights into such fundamental human health issues as cancer and the aging process.

References

www.scienceijrank.org www.cababstractsplus.org www.micrologybytes.com www.wikipedia.org www.bioweb.uwlax.edu www.botit.botany.wisc.edu

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