Cyanobacterial extracellular polymeric substances (EPS): Biosynthesis and their potential applications

Cyanobacterial extracellular polysaccharides (EPS) are high molecular weight hetero-biopolymers having tremendous ecological significance, particularly imparting innate resilience to the microbial communities in nature, and facilitating efficient functioning of ecosystems. Unlike other microorganisms such as eubacteria, archaebacteria, or fungi, cyanobacterial EPS are unique and found as three forms of biopolymers: slime, capsule, and sheath. These EPS vary in nature and composition, depending on the environmental conditions and type of microorganisms in association; often, found associated with pigments and bioactive compounds. This imparts vigor to withstanding considerable inimical conditions such as salinity, heavy metals, drought, and other extreme environments. In recent years, cyanobacterial EPS are considered to be a high-value macromolecule, but their applications are less explored, owing to the poorly documented knowledge regarding the complex nature of these polysaccharides. An overview of the biological properties of cyanobacterial exopolysaccharides toward new state-of-the-art applications, particularly in agriculture, diagnostics, and food industries is discussed. Further, insights into the characteristics, potential applications of this biopolymer in various fields—including environment and industrial biotechnology are illustrated. There is a need to devote more focused efforts towards the in-depth compositional analyses, at both molecular and genetic level. This can help design novel, efficient and effective delivery systems for use, not only in therapeutics, but also in other diverse fields.