Bioremediation of Hexavalent Chromium Contaminated Environments

Hexavalent chromium (Cr(VI)) is a pervasive industrial pollutant recognised for its high solubility, mobility and toxicity. It originates predominantly from electroplating, leather tanning, textile dyeing and metallurgical operations. In the environment, Cr(VI) poses severe risks to human health, aquatic life and soil fertility. Bioremediation harnesses the metabolic capabilities of microorganisms or their by-products to convert Cr(VI) into the much less soluble and less toxic trivalent form (Cr(III)), or to immobilise chromium through biosorption onto biomass. Strategies include in situ treatments such as bioreactor amendments and bioaugmentation, and ex situ processes like packed-bed bioreactors and immobilised enzyme systems. Advances in reactor design, microbial consortia engineering and material science are extending the feasibility of large-scale application. A growing emphasis on sustainable, low-cost and non-toxic approaches has driven research into both fundamental mechanisms of microbial reduction and practical process optimisation for field deployment.

Research from Nature Portfolio

Recent studies have elucidated two complementary pathways in biological Cr(VI) removal. An investigation of sulphate-reducing up-flow anaerobic sludge bed reactors demonstrated that around 90% of Cr(VI) removal was mediated indirectly by biogenically produced sulphide, while the remaining fraction was directly used as an electron acceptor by specific bacteria. The resulting elemental sulphur and extracellular polymeric substances (EPS) were found to protect and stabilise microbial communities under chromium stress. Separately, a biosorption approach using the bacterium Pseudomonas alcaliphila strain NEWG-2 achieved over 96% removal of Cr(VI) at 200 mg L⁻¹ under optimised nutrient and pH conditions. Detailed spectroscopic analyses identified phenolic, carboxylate and carbonyl ester groups as key binding sites, and equilibrium data fitted a Langmuir isotherm, confirming monolayer uptake on immobilised biomass beads. These advances illustrate the integration of biotic sulphide generation and targeted biosorption for efficient Cr(VI) decontamination.

Bioremediation of Hexavalent Chromium Contaminated Environments publication trend

The graph below shows the total number of articles in bioremediation of hexavalent chromium contaminated environments across all publications each year (not limited to Nature Index journals).

Technical terms

Bioremediation: The use of living organisms or their products to detoxify or remove pollutants from the environment.

Hexavalent chromium (Cr(VI)): A highly soluble and toxic oxidation state of chromium that poses significant environmental and health hazards.

Biosorption: The passive binding and concentration of contaminants, such as heavy metals, onto biological materials or biomass surfaces.

Extracellular polymeric substances (EPS): A matrix of polysaccharides, proteins and other polymers secreted by microorganisms that can immobilise contaminants and protect cells.

Sulfidogenesis: A microbial process in which sulphate is biologically reduced to sulphide, which can subsequently reduce metal pollutants such as Cr(VI).

References

1. Formation mechanism of organo-chromium (III) complexes from bioreduction of chromium (VI) by Aeromonas hydrophila. Environment International (2019).
2. Proteomic analysis of the reduction and resistance mechanisms of Shewanella oneidensis MR-1 under long-term hexavalent chromium stress. Environment International (2019).
3. Bioremediation of Chromium by Microorganisms and Its Mechanisms Related to Functional Groups. Journal of Chemistry (2021).
4. An Exploratory Study on the Pathways of Cr (VI) Reduction in Sulfate-reducing Up-flow Anaerobic Sludge Bed (UASB) Reactor. Scientific Reports (2016).
5. Innovative low-cost biosorption process of Cr6+ by Pseudomonas alcaliphila NEWG-2. Scientific Reports (2020).