xylooligosaccharides

Xylooligosaccharides (XOS) are oligosaccharides composed of β-D-xylopyranose units linked mainly by β-1,4-glycosidic bonds. Their degree of polymerization (DP) typically ranges from 2 to 6. Because human digestive enzymes do not readily hydrolyze the β-1,4-xylosidic linkages, XOS pass through the small intestine and are fermented in the colon by specific gut bacteria.

XOS occur naturally in small amounts in certain plant materials, including cereals, fruits, and vegetables, but are typically produced commercially by enzymatic hydrolysis of xylan, a major component of plant hemicellulose. Xylan sources include hardwoods, agricultural residues such as corn cobs and sugarcane bagasse, and wheat or rye bran. Purification concentrates XOS and reduces residual xylose and other sugars; enzymatic processes using xylanases are common, enabling control over DP distribution.

XOS have prebiotic properties: they selectively stimulate the growth of beneficial gut bacteria, notably Bifidobacterium and some Lactobacillus species. Fermentation of XOS yields short-chain fatty acids (acetic, propionic, butyric) and can lower colonic pH. In humans, several studies report improvements in bowel function and potential benefits for mineral absorption and immune function; however, results are not universal and optimal doses are not established. Higher intakes may cause gastrointestinal symptoms such as flatulence and bloating in some individuals.

Applications include use as dietary fiber and prebiotic ingredients in foods and dietary supplements, as well as feed additives for animals. Regulatory statuses vary by country; XOS is commonly regarded as safe for use in foods within specified limits, but product claims and permitted uses depend on local regulations.