Beta-Glucans (or beta-glucans) are polysaccharides occurring in the bran of cereal grains, the cell wall of baker's yeast, certain types of fungi, and many kinds of mushrooms. The cereal based beta-glucans occur most abundantly in barley and oats and to a much lesser degree in rye and wheat. They are useful in human nutrition as texturing agents and as soluble fiber supplements, but problematic in brewing as excessive levels make the wort too viscous. An insoluble (1,3/1,6) beta glucan derived from baker's yeast has a different molecular structure than that of its soluble (1,3/1,4) counterparts and has a greater biological activity due to its structural "branching". Yeast derived beta glucans are notable for their immunomodulatory function. The differences between soluble and insoluble beta glucans are significant in regards to application, mode of action, and overall biological activity.
glucans are polysaccharides that only contain glucose as structural components. Beta 1,3-D glucans are chains of D-glucose molecules, with the six-sided D-glucose rings connected at the 1 and 3 positions. Smaller side chains branch off the 1,3 polysaccharide backbone.The most active form of Beta 1,3-D glucans are apparently those that contain 1,6 side-chains branching off from the longer beta-1,3 glucan backbone. These are referred to as beta-1,3/1,6 glucan. Some researchers have suggested that it is the frequency, location, and length of the side-chains rather than the backbone of beta glucans that determine their immune system activity. Another variable is the fact that some of these compounds exist as single strand chains, while the backbones of other beta-1,3 glucans exist as double or triple stranded helix chains. In some cases, proteins linked to the beta-1,3 glucan backbone may also be involved in providing therapeutic activity. Although these compounds have exciting potential for enhancement of the immune system, it must be emphasized that this research is in its infancy, and there are differing opinions on which molecular weight, shape, structure, and source of beta-1,3 glucans provide the greatest therapeutic benefit.
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