Cyclic β‐1,2‐D‐glucans (CβG) are natural bionanopolymers present in the periplasmicspace of many Proteobacteria. These molecules are sugar rings made of 17 to 25 D‐glucose units linked exclusively by β‐1,2‐glycosidic bonds. CβG are important forenvironmental sensing and osmoadaptation in bacteria, but most importantly, theyplay key roles in complex host–cell interactions such as symbiosis, pathogenesis,and immunomodulation. In the last years, the identification and characterisation ofthe enzymes involved in the synthesis of CβG allowed to know in detail the steps nec-essary for the formation of these sugar rings. Due to its peculiar structure, CβG cancomplex large hydrophobic molecules, a feature possibly related to its function inthe interaction with the host. The capabilities of the CβG to function as molecularboxes and to solubilise hydrophobic compounds are attractive for application in thedevelopment of drugs, in food industry, nanotechnology, and chemistry. More impor-tantly, its excellent immunomodulatory properties led to the proposal of CβGasanew class of adjuvants for vaccine development.
