Yeast is essential in making of bread because it produces:

Yeast is very important in the production of bread. Yeast ferments the sugar in the dough, producing carbon dioxide. The carbon dioxide produced gets trapped in the dough, causing the dough to rise. The dough becomes soft and fluffy.

• It’s not correct to refer to yeast as “bacteria.” Yeast is a fungus. While bacteria are involved in fermentation in some food products, such as yogurt, yeast fermentation of sugar to produce carbon dioxide to make bread rise doesn’t involve bacteria. The substance that makes bread rise is carbon dioxide, not bacteria.