 β-glucans form a natural component of the cell walls of bacteria, fungi, yeast, and cereals such as oat and barley.Each type of beta-glucan comprises a different molecular backbone, level of branching, and molecular weight which affects its solubility and physiological impact.One of the most common sources of β(1,3)D-glucan for supplement use is derived from the cell wall of baker's yeast ("Saccharomyces cerevisiae").