Recent advances in the biological activities of microbial exopolysaccharides

Microbial exopolysaccharides (EPSs) are valuable extracellular macromolecules secreted as capsules or slime layers. Various microorganisms, including bacteria, yeasts, fungi, and algae have been studied for their ability to produce EPSs. Microbial EPSs exist as homopolysaccharides or heteropolysaccharides with various properties such as different monosaccharide compositions, structural conformation, molecular weight, and functional groups. They are cost-effective alternatives to plant and animal-derived polysaccharides because the microbial cells produced them in large quantities by biotechnological processes using low-cost substrates such as industrial wastes in a short time. Microbial EPSs are safe, biodegradable, and compatible polymers. They have extensive bioactivities, including antibacterial, antifungal, antiviral, antioxidant, antitumor, antidiabetic, antiulcer, anticoagulant, antiaging, immunomodulatory, wound healing, and cholesterol-lowering activities. Microbial EPSs owing to biological activities, special biochemical structures, and attractive physicochemical properties find plenty of potential applications in various industries. The enhancement of the production of EPSs and improving their properties can be provided by genetic engineering methods. The current review aims to provide a comprehensive examination of the therapeutic activities of microbial EPSs in infectious diseases and metabolic disorders, with a focus on the mechanisms involved. Also, the effect of the physicochemical characteristics of EPSs on these bioactivities was discussed to reveal the structure-activity relationship.