The word Yeast or Sourdough generally indicates the component used for leavening. The most common yeasts are natural yeast and brewer's yeast.
Sourdough is a traditional technology that improves the quality of baked goods, makes them rise with a wide range of flours and has a positive influence on the final product, improves the consistency, the shelf-life, the taste, but above all the functional and nutritional characteristics of the product.

It exerts a positive influence on the final product, improves the consistency, shelf-life, taste but above all, the functional and nutritional characteristics of the product.
Lactic acid bacteria and yeasts play the most important part in the leavening process.
There are many microbial communities involved in the natural leavening process, including:
- Saccharomyces cerevisiae
- Candida carpophila
- Hyphopicchia pseudoburtonii
- Torulaspora delbrueckii
- Kazachstania humilis
- Kazachstania bulderi
- Kazachstania saulgeensis
- Kazachstania unispora
- Rhodotorula mucilaginosa
In the brewing process, the role of Saccharomyces cerevisiae is to convert sugars from beans into ethanol.

It is used in the food industry as a leavening factor for bread, wine (1), beer (2) and it has some interesting characteristics:
- body purifier
- it helps the bacterial flora to regenerate itself
- it helps the immune defense
- it provides proteins (3)
Contraindications: high dosage, intolerances.
Brewer's yeast has proved to be very useful in the study of degenerative disease Sla as it has allowed to analyze the course of the disease.
This study attributes brewer's yeast a promising activity as an antiulcer and antiproliferative remedy (4).