Biosorption of Heavy Metals Using Extracellular Polymeric Substances

Extracellular polymeric substances (EPS) are high-molecular-weight biopolymers secreted by microorganisms in natural and engineered environments. Comprising polysaccharides, proteins and other functional moieties, EPS form hydrated matrices around cells and mediate adhesion, flocculation and protection. Their abundance of carboxyl, hydroxyl and amino groups enables strong coordination and ion-exchange interactions with heavy metals such as lead, copper, cadmium and chromium. Biosorption harnesses these passive binding processes to remove or recover metals from aqueous media, offering an eco-friendly alternative to conventional treatments. Performance depends on EPS origin, metal chemistry, pH, ionic strength and biomass immobilisation. Recent advances have elucidated adsorption mechanisms, optimised yields through fermentation strategies and demonstrated continuous-flow operation, highlighting EPS as a versatile platform for decentralised remediation and resource recovery within a circular economy.

Research from Nature Portfolio

Research on Klebsiella sp. J1 EPS has established a benchmark biosorbent for lead removal. Maximum uptake of Pb²⁺ reached approximately 100 mg g⁻¹ at pH 6, with adsorption data fitting a Langmuir isotherm and pseudo-second-order kinetics. Thermodynamic analysis indicated a spontaneous, exothermic process. Detailed element balances and spectroscopic assays revealed that ion exchange—principally between Pb²⁺ and native K⁺/Mg²⁺ in the EPS matrix—accounts for over 85 % of the binding. This work provides quantitative insight into functional group contributions, rate-limiting steps and the reusable nature of Klebsiella-derived EPS, serving as a foundation for comparative studies of biosorbent performance.

Biosorption of Heavy Metals Using Extracellular Polymeric Substances publication trend

The graph below shows the total number of articles in biosorption of heavy metals using extracellular polymeric substances across all publications each year (not limited to Nature Index journals).

Technical terms

Biosorption: Passive metal uptake by biological materials through surface binding and complexation, independent of cell metabolism.

Extracellular Polymeric Substances (EPS): Secreted biopolymer assemblies, primarily polysaccharides and proteins, that form hydrated matrices facilitating adhesion and metal sorption.

Ion Exchange: Mechanism where metal ions in solution replace cations bound to functional groups within the EPS network.

Langmuir Isotherm: Adsorption model describing monolayer uptake onto homogeneous sites with finite capacity.

Pseudo-second-order Kinetic Model: Rate model assuming chemisorption through electron sharing or exchange controls the adsorption process.

References

1. Biosorption of Pb (II) from aqueous solution by extracellular polymeric substances extracted from Klebsiella sp. J1: Adsorption behavior and mechanism assessment. Scientific Reports (2016).
2. Regeneration and reuse of microbial extracellular polymers immobilised on a bed column for heavy metal recovery. Water Research (2020).
3. Impacts of metal stress on extracellular microbial products, and potential for selective metal recovery. Ecotoxicology and Environmental Safety (2023).
4. Hyperproduction of extracellular polymeric substance in Pseudomonas fluorescens for efficient chromium (VI) absorption. Bioresources and Bioprocessing (2023).