Yeast is actually a tiny microorganism, classified in the plant kingdom of Fungi. The mushroom or mold variety, feeds on the natural sugars which are found in grains, fruits, and vegetables. This process in turn helps in producing carbon dioxide as a byproduct of its consumption.

What is the source of yeast?

They are commonly found on plant leaves, flowers, and fruits, as well as in soil. Yeast are also found on the surface of the skin and in the intestinal tracts of warm-blooded animals, where they may live symbiotically or as parasites. The common "yeast infection" is typically caused by Candida albicans.

Where does yeast for bread come from?

The strains of yeast used to make beer, bread, and wine come from the species of yeast called Saccharomyces cerevisiae. S. cerevisiae is known as “brewer's yeast” or “baker's yeast” for good reason: it's responsible for the fermentation that makes beer alcoholic and allows a lump of dough to rise into a loaf of bread.