oligosaccharides

An oligosaccharide is a carbohydrate composed of a small number of monosaccharide units, typically 3 to 10, linked by glycosidic bonds. This places oligosaccharides between monosaccharides and polysaccharides in size. They may be linear or branched and can contain various monosaccharide types such as glucose, galactose, fructose, or mannose. Common examples include raffinose and stachyose from the raffinose family, as well as fructooligosaccharides (FOS) and galactooligosaccharides (GOS), which are widely used as prebiotics.

In biology, oligosaccharides occur as parts of glycoproteins and glycolipids, where short chains extend from proteins or lipids and contribute to folding, stability, and cell recognition. They play roles in development, immune signaling, and host–microbe interactions. Oligosaccharides differ from disaccharides (two units) and polysaccharides (long polymers) in size and often in function.

Digestive fate and applications: In humans, many oligosaccharides are not hydrolyzed by endogenous enzymes and reach the colon, where gut microbiota ferment them to short-chain fatty acids, with possible gas production. This property underlies their use as prebiotics. Some oligosaccharides are produced commercially for nutrition and food formulation, while others are studied for their roles in health and disease. Synthesis occurs via glycosyltransferases in living organisms or by chemical and enzymatic methods in the laboratory. Enzymes called glycosidases hydrolyze them to their constituent monosaccharides.