Name the micro-organism used in bread-making which makes the bread-dough rise. How does it make the dough rise?

Baker's yeast, scientifically named Saccharomyces cerevisiae, is the microorganism used in bread-making that causes dough to rise and develop its characteristic light, fluffy texture. This single-celled fungus has been used in baking for thousands of years and is available commercially as active dry yeast, instant yeast, or fresh compressed yeast. When mixed into bread dough containing flour, water, sugar, and salt, the yeast cells begin metabolizing available sugars through the fermentation process.

The rising action occurs because yeast fermentation produces carbon dioxide gas as a byproduct when breaking down sugars under the warm, moist, low-oxygen conditions inside dough. These carbon dioxide bubbles become trapped within the gluten network—an elastic protein matrix formed when wheat flour is mixed with water and kneaded. As fermentation continues, thousands of tiny gas bubbles accumulate and expand, causing the dough to increase in volume, sometimes doubling or tripling in size during the rising or "proofing" period. Yeast also produces small amounts of alcohol and organic compounds that contribute to bread's flavor and aroma, though the alcohol evaporates during baking. The subsequent baking process kills the yeast while heat causes final gas expansion and sets the bread's spongy, aerated structure. Optimal yeast activity occurs at warm temperatures (around 25-30°C), which is why dough is typically left to rise in a warm place.