Yeast lives an obligate or facultative anaerobic life. Unknown obligate anaerobic yeasts. When there is a lack of oxygen, fermenting yeasts obtain it by converting sugars into carbon dioxide and ethanol (commonly known as alcohol). energy.

Yeast produces a large amount of carbon dioxide during dough fermentation, and due to the formation of gluten network tissue, it is retained in the network tissue, making the baked food tissue loose and porous and increasing in volume