Glucan, is a polysaccharide material, exists in certain microorganisms in the secretion of mucus during the growth process, divided into α-glucan and β-glucan, and later University of Tulun Diluzio in baker's yeast Which was able to enhance the resistance of the material identified as β-glucan.

Β-glucan is widely found in yeast, mushrooms, oats and barley and other foods, which β-1,3 / 1,6 exist in yeast and mushroom dextran, and β 1,3 / 1,4 exist in Oat and barley dextran.

Β-glucan with ordinary common carbohydrates (such as starch, glycogen, dextrin, etc.) is not the most important difference is that the bond is not the same way, the general structure of the sugar carbohydrate α-1,4-glycosides Β-glucan is a β-1,3-glucosidic bond as the main body, and contains some β-1,6-glucosidic linkages. Β-glucan because of its special bond mode and the presence of intramolecular hydrogen bonds, resulting in a spiral of molecular structure, this unique configuration is easily accepted by the immune system. Therefore, when it comes to immunity have to mention the important role of yeast glucan.