Role of Cyanobacterial Exopolysaccharide in Soil Fertility: Composition, Mechanism and Application

Ecosystem stability and sustainable agriculture are seriously threatened by land degradation and deteriorating soil quality. Nutrient loss, structural instability, and microbial imbalance are accelerated by elements including intensive farming, erosion, salinization, heavy metal contamination, and climate stress. Cyanobacteria produce exopolysaccharides (EPS), which have become environmentally benign agents for soil rehabilitation. Different sugars, uronic acids, and functional groups that offer excellent water-holding capacity, negative charge, and metal-binding ability are present in these high-molecular-weight heteropolymers. The production of EPS increases under stress to improve microbial survival and biofilm formation. EPS biosynthesis takes place via conserved pathways and is controlled by environmental factors. EPS binds particles through physicochemical interactions in soils, promoting biological soil crust development, aggregation, and structural stability. Their hydrogel characteristics increase nutrient availability, decrease leaching, and promote water retention, porosity, and aeration. Furthermore, EPS helps in soil detoxification by immobilizing harmful metals via chelation and biosorption. They support microbial diversity, nitrogen fixation, rhizosphere interactions, and long-term carbon sequestration. Slurry inoculation, EPS spraying, soil assimilation, and integration with organic amendments are examples of useful applications. All things considered, cyanobacterial EPS offer a versatile and sustainable method for repairing damaged soils and boosting agricultural resilience.