Mitigating chromium (VI) toxicity through microbial and biotechnological innovations: a critical review

Abstract Hexavalent chromium [Cr (VI)] is a prevalent and highly toxic environmental contaminant known for its persistence and severe ecological and health consequences. Its high solubility and mobility contribute to long-lasting pollution, while its carcinogenic properties pose significant risks to living organisms. Conventional physicochemical methods such as precipitation, ion exchange, and membrane filtration are employed for Cr (VI) removal but often suffer from drawbacks including high costs, incomplete elimination, and generation of secondary pollutants. In contrast, microbial and biotechnological methods offer sustainable, environmentally friendly alternatives for detoxifying Cr (VI). This review focuses on microbial remediation strategies, including biosorption, bioaccumulation, biotransformation, and bioleaching, with particular attention to the roles of bacteria and fungi. Key factors discussed include microbial resistance genes and enzymatic systems that facilitate the reduction of Cr (VI) to the less harmful Cr (III). Advances in designing microbial consortia, understanding genetic regulation, and integrating bioprocess engineering are also explored to enhance remediation efficacy. Comparing traditional and biological approaches highlights the superior sustainability and scalability of microbial systems for large-scale environmental treatment. Innovations in microbial bioremediation through biotechnological approaches present a promising path forward for mitigating chromium pollution and restoring environmental health in contaminated ecosystems.