Microbial exopolysaccharides in environmental remediation: production, mechanisms, and challenges.

Microbial exopolysaccharides (EPS) are increasingly recognized as effective, biodegradable, and low-toxicity biomaterials for the remediation of heavy metal-contaminated environments. Their high metal-binding capacity, chemical tunability, and microbial renewability make EPS attractive alternatives to conventional physicochemical adsorbents. Although numerous studies have reported the application of EPS in the removal of heavy metals and other toxic pollutants, existing literature remains fragmented, with limited integration of EPS production pathways, structure-function relationships, comparative adsorption performance and limited guidance on scalable production strategies. A key contribution is a consolidated comparative analysis of adsorption capacities of EPS, derived from different microbial taxa against major heavy metals, enabling informed selection of high-performing EPS systems for remediation applications. Furthermore, the review systematically categorizes the major metabolic pathways involved in EPS biosynthesis and identifies key microorganisms utilizing these pathways, highlighting regulatory factors influencing EPS yield and composition. Special emphasis is placed on bioreactor-based EPS production strategies, including batch, fed-batch, and continuous systems, and their role in improving productivity, consistency, and scalability. Emerging approaches such as EPS-based nanocomposites, hybrid materials, and bioengineered microbial systems are also discussed as promising solutions to overcome these limitations. This article provides a comprehensive and critical synthesis of microbial EPS in environmental remediation, focusing on their biosynthesis pathways, physicochemical characteristics, and adsorption mechanisms governing pollutant sequestration. By integrating microbial physiology with performance-oriented remediation outcomes, this review identifies critical bottlenecks and future research priorities required to advance microbial EPS from laboratory demonstrations toward cost-effective and scalable environmental remediation technologies.