How does yeast make bread dough rise?

Yeast makes bread dough rise through a biological process known as fermentation.12

When bakers’ yeast—typically the species Saccharomyces cerevisiae—is added to dough, it consumes available sugars present in the flour or added as ingredients. As the yeast metabolizes these sugars, it produces carbon dioxide gas and ethanol as byproducts.314

The carbon dioxide gas becomes trapped within the elastic structure of the dough, causing it to expand and rise. This process, often referred to as proofing, is essential for creating the characteristic airy texture of bread. While the ethanol produced during this reaction contributes to the aroma of the bread, it is driven off during the baking process. The rate of this rising action is influenced by environmental factors, particularly temperature and osmotic pressure, which must be managed to ensure the quality of the final product.2314