Rediscovering bacterial exopolysaccharides of terrestrial and marine origins: novel insights on their distribution, biosynthesis, biotechnological production, and future perspectives.

Bacteria exist in colonies as aggregates or associated with surfaces forming biofilms rather than planktonic cells. Living in such a unique manner is always mediated via a matrix of extracellular polymeric substances, which are composed mainly of polysaccharides or specifically exopolysaccharides (EPS). Biofilm formation and hence EPS production are affected by biotic and abiotic factors inducing/inhibiting several involved genes and other molecules. In addition, various aspects of bacterial EPS regarding: physiological functions, molecular weight, and chemical composition were demonstrated. Recent investigations have revealed a wide spectrum of EPS chemical and physicochemical properties showing promising applications in different industrial sectors. For instance, lactic acid bacteria (LAB)- and marine-derived EPS exhibit: immunomodulatory, antioxidant, antitumor, bioremediation of heavy metals, as well as thickening and viscosity modifiers in the food industry. However, bacterial EPS have not yet been commercially implemented, in contrast to plant-derived analogues. The current review aims to rediscover the EPS structural and biosynthetic features derived from marine and terrestrial bacteria, and applications as well.