The yeast used for steaming buns and the yeast used for brewing are not the same, the yeast used for steaming buns only has the ability to make flour. The yeast used for brewing, more precisely, is not yeast used for brewing, but wine song. The main components of the wine song are root mold, trichoderma and a small amount of yeast. The root molds in the brew can break down the starch in the grain into sugar, and then the sugar can be used to produce alcohol and carbon dioxide under the action of the yeast.