Introduction: As industrial activities continue to increase, the introduction of heavy metals into water sources has risen. Various reports indicate that the presence of heavy metals in water leads to a range of health problems. Researchers have identified lead exposure as a cause of neurological disorders, including reduced intelligence and behavioral issues in children, kidney damage, and blood system abnormalities (1,2). Cadmium exposure has been linked to kidney impairment—specifically protein reabsorption defects—osteoporosis, increased cancer risk, and respiratory problems (3,4). Additionally, elevated levels of copper, nickel, zinc, and cobalt have been associated with gastrointestinal issues, liver and kidney damage, and in some cases, neurological effects. Zinc and nickel, in particular, have been reported to contribute to respiratory disorders, skin sensitivities, and systemic toxicity (5,6).in this case fungi would be a great green tool to remove heavy metals.
Methods: Compared to traditional chemical or physical methods, this approach is more cost-effective, environmentally friendly, and safer, without the risk of producing or releasing new metals. Moreover, most fungi used for biosorption are non-pathogenic.
Various functions and mechanisms of fungi, such as mycoremediation, bioprecipitation, bioaccumulation, bioprecipitation, bioreduction, and biomineralization, play a direct role in the removal of heavy metals and assist us in the purification process.
Studies have shown that Pleurotus eryngii is an effective candidate for mycoremediation(12).
In one study, the white-rot fungus Phanerochaete chrysosporium demonstrated the ability to reduce active lead ions through mechanisms such as adsorption, cation exchange, and chelation (13,14).
In another investigation, living cells of this fungus were used for lead removal, and the stabilization of lead in the form of lead oxalate and lead phosphate chloride was confirmed several days after exposure(15).
In one study, the use of Phanerochaete chrysosporium was reported for the removal of cadmium, cobalt, and copper (16). In another investigation, Aspergillus niger was examined for its ability to remove chromium, zinc, and cobalt (17). Additionally, in a separate study, three fungi— Paecilomyces sp., Penicillium sp. and Aspergillus niger—were found to be effective in cobalt removal (18).
Results: Fungi, with cell walls rich in polysaccharides, proteins, and lipids, contain active functional groups such as -OH، -COOH، -NH2 و -PO4 groups that enable them to passively (non-metabolically) adsorb heavy metals. This means that fungi do not produce heavy metals themselves but rather absorb and retain them within their structure (7).Fungi can produce non-specific oxidoreductase enzymes such as laccases, peroxidases, and other oxidases, which enable them to degrade or transform complex or toxic compounds. In some cases, they can also convert toxic metals into less harmful forms. This contributes to maintaining clean water without generating new metals (8).
The efficiency of purification—essentially the amount of metal absorbed by the fungi—depends on factors such as metal concentration, pH,temperature, contact time, and biomass amount. In addition, the fungal species also influences the level of absorption (9).
A recent approach involves the application of dried mycelial membranes, which have demonstrated high efficiency in removing lead ions from aqueous solutions. In this research, Phanerochaete chrysosporium, and Pleurotus ostreatus were used (10). In another research method as well, various factors such as contact time, pH, and biomass dosage have proven to be effective (11).
Conclusion: Fungi used for water purification are environmentally friendly tools for the removal of heavy metals from water. They absorb, reduce, or stabilize metals without generating any new metallic compounds. Their effectiveness depends on environmental conditions and the suitability of fungal species. The use of dried fungal biomass or non-specific enzymes can further enhance the efficiency of this method.