Synthetic Biology and Genetic Engineering Strategies for Microbial and Algal Bioremediation of Heavy Metals: A Scoping Review

Heavymetal contamination persists in water, soil, and sediments owing to its toxicity, bioaccumulation potential, and continuous inputs from mining, metallurgy, and ewaste processing. Synthetic biology offers a route to engineer microbes and microalgae with metalspecific uptake, binding, and redoxtransformation capabilities that outperform conventional physicochemical treatments. We conducted a PRISMAScR scoping review of peerreviewed literature indexed in Scopus and PubMed (January 2015 – May 2025). After screening 941 records, 69 studies met the inclusion criteria. Bacterial chassis dominated (almst 90 % of studies), principally E. coli and C. metallidurans , whereas engineered alge (25 %) and funi (25 %) remain underrepresented. Multimetal remediation designs accounte for 61 % of experimental work, ye only 8 % progressed to pilot scae and 6 % to field trials. Reported interventions improved metalremoval efficiencies 1.5–3fold and increased LC₅₀ tolerance two to fourfold relative to wildtype strains. Key barriers to deployment include genetic stability, biosafety and containment, cost of inducers, and limited performance data under complex environmental matrices.This review provides the first decade‑scale synthesis of synthetic‑biology strategies for microbial and algal heavy‑metal remediation, offering a quantitative map of chassis selection, genetic toolkits, and mechanistic pathways. By identifying technology bottlenecks, particularly biosafety governance and field‑scale validation it outlines a research agenda for translating laboratory advances into sustainable environmental applications that support SDGs 6 and 12.