Glycosides as compatible solutes: biosynthesis and applications

Osmolytes are low-molecular-weight organic solutes whose intracellular formation in high concentrations presents a universal biological mechanism through which the cell copes with the hyperosmolality of the extracellular environment. Because macromolecular structure and function is usually not perturbed and many proteins are structurally stabilized at high osmolyte concentration, the term "compatible solute" is often used for osmolytes. The diversity of the known compatible solutes is broad, and includes glycosides as an important structural class. The glycosides, prototypically represented by 2-O-alpha-D-mannosyl D-glycerate, are widespread among Bacteria and Archaea. They are often associated with microbial life under extremes of salt concentration, temperature and nutrient limitation. Herein, we review salient features of glycosides as compatible solutes, focusing on the enzymology of their biosynthesis. Possible routes for production of glycosidic solutes as industrial fine chemicals are described. Their (potential) use in health-care, cosmetic and food applications is discussed. 2-O-alpha-D-Glucosyl-sn-glycerol is the first among the glycosidic solutes that has become commercialized at an industrial scale.