Microalgae-based strategies for cadmium remediation: insights, challenges, and future directions

Cadmium (Cd²⁺) pollution possesses severe risks to human health and the ecosystem due to its high toxicity, persistence, and bioaccumulation potential. Conventional remediation methods, such as chemical precipitation, membrane filtration and ion exchange, are often costly, inefficient and unsustainable. In contrast, microalgae-based bioremediation has emerged as a promising approach due to its ability of biosorption, bioaccumulation and biotransformation. Microalgae possess unique metabolic and structural attributes, including: abundant extracellular metal binding sites, polymeric substances, intracellular chelators and the ability of Cd-nanoparticles (CdSeNPs, CdSNPs) formation enabling efficient Cd²⁺ sequestration and detoxification. Despite these advantages, large-scale application remains limited due to gaps in understanding of key regulatory mechanisms. This review highlights the detailed mechanism of the microalgae-based Cd²⁺ remediation process, identifies critical factors influencing remediation efficiency and potential microalgae strain's efficiency in Cd²⁺ removal. Furthermore, the utilization of genetic engineering for enhancing remediation efficiency by targeting key metal transporters, chelators, and stress-response pathways and potential candidate gene are also highlighted. These biotechnological advances and the understanding of the microalgae mediated remediation process presents a promise for a large scale efficient, sustainable Cd²⁺ bioremediation approach.