Biological synergies for heavy metal bioremediation across microbial, algal, and phytoremediation perspectives

Heavy metal pollution continues to threaten ecosystem and human health due to the persistence, non-degradability, and toxicity of metals such as Cd, Cr, Pb, Hg, and As. Microbial, fungal, algal, and plant-based bioremediation systems demonstrate high metal removal efficiencies, with biosorption capacities ranging from 70 to 99% for fungi (e.g., Aspergillus, Penicillium), 60–98% for bacteria (e.g., Bacillus, Pseudomonas), 40–95% for algae (Chlorella sp., Oedogonium sp.), and 30–80% for plants depending on species and metal bioavailability. Engineered microbial strains and CRISPR-edited plants exhibit enhanced uptake, with CRISPR knockouts in rice reducing Cd accumulation in grains by up to 70%. In contrast, microbial consortia remove metals more efficiently than single strains, achieving 98–100% remediation at optimized pH (5.5–7.5) and metal concentrations (10–100 mg/L). Despite strong laboratory performance, field translation is limited by inconsistent metal bioavailability, environmental variability, and long remediation times. This review synthesizes comparative efficiencies, mechanistic foundations, and scalability challenges, highlighting integrated nano-bioremediation, microbial consortia, and genome-edited plants as promising next-generation strategies toward sustainable heavy metal mitigation.