What Is Yeast?

what is yeast

Yeast is a single-celled microorganism that is a member of the Fungi kingdom. Yeast is found in nature and within our bodies; it consumes sugar and produces by-products such as carbon dioxide, alcohol, and other chemical compounds. Yeast is an essential ingredient in baking, brewing, and winemaking.

yeast, any of about 1,500 species of single-celled fungi, most of which are in the phylum Ascomycota, only a few being Basidiomycota.

Yeasts are found worldwide in soils and on plant surfaces and are especially abundant in sugary mediums such as flower nectar and fruits. There are hundreds of economically important varieties of ascomycete yeasts; the types commonly used in the production of bread, beer, and wine are selected strains of Saccharomyces cerevisiae.

Some yeasts are mild to dangerous pathogens of humans and other animals, especially Candida albicans, Histoplasma, and Blastomyces.

what is yeast

Characteristics Of Yeast

General characteristics of Yeast

  • Yeast is basically chemorganotrophs as they can use the inorganic chemical as a source of energy.
  • Mostly yeast is isolated from the surfaces of fruit and berries like apples, peaches, and exudates from plants such as plants saps or cacti.
  • Yeast can be present in the gut flora of mammals and some insects and even in the deep-sea environment.
  • Yeast mostly grows at a temperature ranging between 20 to 28 degrees Celsius at an acidic pH of 3.5 to 4.
  • For maintenance and preservation of yeast culture slant with 2%, caco3 can be used.
  • Classification of yeast can be done using its morphological characteristics, cultural characteristics and sexual characteristics, and physiological characteristics.

Morphological characteristics

  • The characteristics of vegetative reproduction and a vegetative cell can be used to classify yeast.
  • Vegetative reproduction is done either by fission or by budding or the formation of conidia.
  • Reproduction by fission is a typical characteristic of endomycetacea.
  • Morphology of the vegetative cells cultivated in liquid and solid media is founded on whether the cells are spherical, ovoid, cylindrical, etc.

Cultural characteristics

  • Yeast grown in watery media may result in the formation of residue a ring, or a pellicle.
  • Pellicle formation on a watery medium is a product associated with the oxygen demand of yeast.
  • Growth on solid media may be butyrous, friable, and pigmented.
  • Lipomyces shows characteristics of mucoid growth.

Physiological characteristics

  • Yeast developing on a carbon source must either be able to format it or utilise it by respiration.
  • It has been found that when yeast utilises carbon source fermentatively it is also able to utilise it oxidatively.
  • The ability or inability to ferment carbohydrates to ethanol and carbon dioxide is the most important for differentiating spaces.
  • Variety of sugars is formatted by a variety of yeast.
  • Nitrogen metabolism is the fundamental feature of development the ability or inability to utilise various derivations of nitrogen can be made use of in classifying yeast.
  • The use of the ability or inability to grow in a synthetic medium devoid of vitamins like biotin and folic acid, inositol etc.
  • Except for genus saccharomyces which only grows in media containing certain east or protein hydrolysates all yeast can utilise a variety of nitrogen sources.
  • Practically every yeast uses urea at low concentration as a single source of nitrogen contributed that a sufficient amount of vitamins are supplied.
  • Fermentative yeast from a variety of oysters is varying amounts.
  • Ethyl acetate has been found to be the commonest and the most readily detectable Easter formed by yeast.
  • It is approved that the potential of yeast to soften gelatin is a very restricted taxonomic importance as very few are strongly proteolytic.

What are the common Uses of Yeast?

Yeast is a single-celled organism that reproduces asexually and has been used in baking and brewing for thousands of years. There are at least 1,500 species of yeast, all of which are technically living organisms. Yeast occurs naturally in the environment and is in the same biological family as fungi such as mushrooms.


The most common use of yeast has been in the making of bread. The yeast reacts with oxygen and helps leaven bread, or make it rise. During Passover, Jewish people will remove the yeast from bread to make flatbread. There is evidence the ancient Egyptians used yeast to make bread around 4,000 years ago.

Alcoholic Drinks

Brewing wine and beer has also used yeast for centuries to ferment the mixture to make it alcoholic. Different kinds of yeast are used to make ale, lager, spirits and wine. It makes alcohol by reacting with the sugars that naturally occur in these drinks.

Non-Alcoholic Drinks

Root beers and other soft drinks use yeast to add flavor, but the fermentation process is stopped before the drink becomes alcoholic. This means the drinks are much sweeter than their alcoholic counterparts and contain more carbon dioxide. They also normally have a very low alcohol content, although this is usually around 0.1 percent.

Scientific Research

Due to the cellular makeup of yeast, many scientists use it to learn more about human genetics. Studies of yeast cultures led directly to the mapping of the human genome.


Most recently yeast has been used in the production of biofuels. This is because the yeast turns sugar into ethanol which can be used as a diesel substitute in vehicles. The process it goes through is identical to that of making beer or wine.


Many of the probiotic drinks available now use yeast as a supplement. Many vegetarians use yeast as a supplement due to low protein and vitamin amounts in their normal diet.

Yeast Extract

Yeast can also be processed to create yeast extract. This is then used in a variety of food products such as Marmite and Vegemite.

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