Beyond carbon capture: bioengineering cyanobacteria as solar-driven platforms for remediation of recalcitrant...

Cyanobacteria are increasingly positioned as photosynthetically powered, genetically tractable chassis for next-generation environmental remediation-operating as living filters that couple solar energy capture to active detoxification and resource recovery. This review synthesizes current advances in cyanobacteria-based remediation of heavy metals, micro- and nanoplastics, pathogens, and persistent organic pollutants, with particular emphasis on metabolic mechanisms, bioengineering strategies, and practical environmental applications. This review outlines a bioengineering roadmap for deploying cyanobacteria in wastewater and impacted aquatic systems to sequester and reclaim toxic heavy metals, trap nano/microplastics, attenuate pathogenic microorganisms, and chemically degrade recalcitrant organic pollutants. In the field of metal capture, recent advances in "living materials" have enabled the embedding of cyanobacteria in regenerable matrices for efficient removal and subsequent reclamation. Mechanistic insights into species such as Synechocystis have clarified adsorption behavior and stress-response determinants for cadmium and related metals, defining tunable targets including transporters, exporters, and chelation modules for strain improvement. Cobalt and uranium handling can now be rationally engineered by rewiring metal homeostasis systems or exploiting high-capacity biosorption using scalable biomass platforms like Spirulina. Beyond metals, cyanobacterial extracellular polymeric substances (EPS) are being leveraged as engineered bio-based flocculants to remove polystyrene micro- and nanoplastics, while consortia-based designs are emerging to facilitate polymer transformation. Collectively, these advances motivate the development of modular, field-ready cyanobacterial platforms immobilized, sensor-guided, and biocontained that integrate pollutant capture and circular recovery within sustainable photobioremediation pipelines. However, significant challenges remain, including field-scale validation, environmental variability, biosafety considerations, biomass management, economic feasibility, and regulatory constraints. Addressing these limitations will be essential for the practical implementation of cyanobacterial remediation technologies.