What is Yeast?
Yeast is a key element in the production of industrial ethanol, but do you know the specificities of this microorganism?
Yeast is a unicellular fungus
Yeast belongs to the family of the fungi. It consists of a large and diverse group of eukaryotic organisms, i.e. they possess organelles that divide the cell space into specialized compartments. The nucleus, for example, contains their genetic heritage (DNA). Fungi are heterotrophic in nature, they feed on existing organic constituents to synthesize the components they need.
There are 3 major groups of fungi: macroscopic filamentous fungi (whose fruiting body is called mushroom), microscopic multicellular filamentous fungi (molds) and microscopic unicellular organisms (yeasts).
Saccharomyces cerevisiae: the most popular species
Not all yeasts look the same. Even if the oval shape dominates, the shape varies depending on the species. Did you know that there are several thousand yeast species? The number of yeasts discovered is constantly increasing. In 2005, only 2,500 species were identified out of the 150,000 that the Earth could host.
Among this great diversity, the species most used for bioethanol production is certainly Saccharomyces cerevisiae. Its name is a combination of Greek and Latin: in Greek, Saccharo means sugar, myces means fungus and cerevisiae is derived from a Latin word meaning “of beer”.
Thanks to its high ethanol productivity, high tolerance to ethanol and ability to ferment a wide range of sugars, it is not surprising that this species has been used since antiquity to produce alcoholic beverages.
Yeasts are used in many industrial applications to produce a wide variety of food, feed and industrial products. One of the most common applications is in the bakery industry, where its fermenting capacity is used to leaven the dough. Moreover, its biochemical composition makes it an interesting product for nutrition applications. Indeed, Saccharomyces cerevisiae is rich in vitamins and minerals which, when ingested by a living being, whether human, animal or vegetable, contribute to the proper functioning of its organism.
Finally, as a eukaryote, its cellular mechanisms are very similar to human cells. Thus over the years, S. cerevisiae has become a model microorganism in molecular and cellular biology for studying biochemical reactions in the cell.
Source:  Azhar SHM, Abdulla R, Jambo SA, Marbawi H, Gansau JA, Faik AAM, Rodrigues KF. Yeasts in sustainable bioethanol production: a review. Biochemistry and Biophysics Reports 2017; 10: 52-61.