Biotransformation of xylo-oligosaccharides by lactic acid bacteria into valuable bioactive compounds: A short review

Xylo-oligosaccharides (XOSs) are oligosaccharides composed mainly of multiple D-xylose (pentose) monomers linked by β-(1,4) xylosidic bonds, with a degree of polymerization mostly ranging from 2 to 10 units. XOSs are recently emerging as important prebiotics used as food additives. They can be obtained from agricultural residues naturally rich in xylans (fruits, sugar cane bagasse, chestnut shells, wheat straw, peanut shells, honey, etc.). Lactic acid bacteria (LAB) are commonly used in the food and non-food industries, due to their status generally recognized as safe (GRAS), and their ability to produce a variety of important glycosides hydrolases (i.e. -xylosidases), releasing mono- and oligosaccharides (xylose, xylobiose, xylotriose, etc.) from XOSs. The xylose (pentose), obtained as the major monomer end product, can be fermented by some LAB into various valuable biomolecules (organic acids, ethanol, short-chain fatty acids, hydrogen peroxide, bacteriocins, vitamins, exopolysaccharides, etc.). These biomolecules are known for their important biological properties (e.g. antioxidant, antibacterial, antifungal, antidiabetic, tackling vitamin B deficiency, etc.). They can be used as nutraceuticals and bio-preservatives in the food industry. In this review, we summarize the current state of the literature on the biotransformation of XOSs by LAB, as well as the biological properties of their fermentation products.