Simultaneous Removal of Heavy Metals and Production of Fungal Enzymes

Heavy metals released into the environment need to be treated due to their detrimental effect on health and ecological balance. Heavy metals can be treated by physical, chemical, or biological approaches. However, the physical and chemical methods are often associated with disadvantages such as high cost, secondary sludge generation, and inefficacy at lower concentrations. Biological methods involve biosorption, biotransformation, and biomineralization. Fungi with better cell wall properties for heavy metal sequestration and the ability to tolerate extreme conditions make it a suitable biological system for heavy metal removal. Fungal biomass, either live or dead, can be used for heavy metal biosorption by metabolism-dependent (bioaccumulation) or metabolism-independent mechanisms. Fungi can transform heavy metals into less toxic materials by altering the oxidation state or by methylation or dealkylation process. Apart from this, fungi can mineralize metals by precipitating metals to metal carbonates and phosphates by the action of released enzymes such as urease and phosphatase. Remediation of heavy metals using fungi can be made cost-effective with the co-production of enzymes. The use of fungi for heavy metal removal by biosorption, biotransformation, and biomineralization involves the action of many enzymes. Identifying and optimizing the co-production of enzymes like catalase, peroxidase, laccase, urease, phosphatase, and lipase during fungal metal removal could transform fungal bioremediation into a more sustainable and cost-effective technique. Moreover, the production of antioxidant enzymes such as superoxide dismutase and catalase can be induced during biosorption. This chapter envisages routes of heavy metal removal by fungal biomass; various enzymes involved during heavy metal removal using fungal; and strategies employed for the co-production of enzymes during heavy metal remediation.