An oligosaccharide is a saccharide polymer containing a small number (typically three to ten[1]) of component sugars, also known as simple sugars (monosaccharides). The name is derived from the Greek word oligos, meaning "a few", and from the Latin/Greek word sacchar which means "sugar". Oligosaccharides can have many functions; for example, they are commonly found on the plasma membrane of animal cells where they can play a role in cell-cell recognition.
They are generally found either O- or N-linked to compatible amino acid side chains in proteins or to lipid moieties (see glycans).
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Fructo-oligosaccharides (FOS), which are found in many vegetables, consist of short chains of fructose molecules. (Inulin has a much higher degree of polymerization than FOS and is a polysaccharide.) Galactooligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans.
Oligosaccharides are often found as a component of glycoproteins or glycolipids and as such are often used as chemical markers, often for cell recognition. An example is ABO blood type specificity. A and B blood types have two different oligosaccharide glycolipids embedded in the cell membranes of the red blood cells, AB-type blood has both, while O blood type has neither.
Mannan-oligosaccharides (MOS) are widely used in animal feed to encourage gastrointestinal health and performance. They are normally obtained from the yeast cell walls of Saccharomyces cerevisiae. Some brand names are: CitriStim, Bio-Mos, SAF-Mannan, Y-MOS and Celmanax.
When oligosaccharides are consumed, the undigested portion serves as food for the intestinal microflora. Depending on the type of oligosaccharide, different bacterial groups are stimulated or suppressed.
Clinical studies have shown that administering FOS, GOS, or inulin can increase the number of these friendly bacteria in the colon while simultaneously reducing the population of harmful bacteria.[2]
FOS and inulin are found naturally in Jerusalem artichoke, burdock, chicory, leeks, onions, and asparagus. FOS products derived from chicory root contain significant quantities of inulin, a fiber widely distributed in fruits, vegetables and plants. Inulin is a significant part of the daily diet of most of the world’s population. FOS can also be synthesized by enzymes of the fungus Aspergillus niger acting on sucrose. GOS is naturally found in soybeans and can be synthesized from lactose (milk sugar). FOS, GOS, and inulin are available as nutritional supplements in capsules, tablets, and as a powder.
Not all natural oligosaccharides occur as components of glycoproteins or glycolipids. Some, such as the raffinose series, occur as storage or transport carbohydrates in plants. Others, such as maltodextrins or cellodextrins, result from the microbial breakdown of larger polysaccharides such as starch or cellulose.
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