Yeast and some bacteria ferment sugars, producing ethyl alcohol and carbon dioxide (CO2), a process called alcoholic fermentation.
In alcoholic fermentation, the two produced pyruvic acid molecules are converted into ethyl alcohol (also called ethanol), with the release of two CO molecules.2 and the formation of two ATP molecules.
This type of fermentation is carried out by various microorganisms, especially the so-called “beer fungi” of the species Saccharomyces cerevisiae. Man uses the two products of this fermentation: ethyl alcohol used for millennia in the manufacture of alcoholic beverages (wines, beers, cachaça, etc.), and carbon dioxide important in the manufacture of bread, one of the most traditional foods of mankind. More recently these fungi have been used for the industrial production of fuel alcohol.
Fermenting fungi are also able to breathe aerobically, if there is oxygen in the middle of life. As a result, the glucose they use is more deeply transformed and the energy balance is higher, 38 ATP, than the 2 ATP obtained in fermentation.