# Mycoremediation as a Potentially Promising Technology: Current Status and Prospects--A Review
## 6 Mechanisms of Mycoremediation
### Bisorption  
Biosorption is a biotechnological technique to remediate heavy metals (HMs) using living and non-living fungi, bacteria, and algae. It is a physicochemical process in which hazardous substances from biological sources are absorbed through ion exchange, reduction, precipitation, chelation, and adsorption [191].  
Biosorption uses a solvent (liquid phase) and a biosorbent (solid phase), and the solvent prevents the sorption of dissolved material [192]. Numerous industrial, agricultural, and natural waste products have been used as biosorbents; nevertheless, biomass from fungi has attracted much interest due to its significant amount of biosorbent. The fungal cell wall is the first biological component to interact with pollutants. It plays a crucial role as a barrier and protective layer that controls the uptake of potentially hazardous metals into the cell. The biosorption efficiency of fungal species can be significantly affected by changes in the cell wall structure or the environment of the fungal biomass. _Neosartora fischeri_ and _Aspergillus fumigatus_, for example, significantly reduced their As(V) biosorption capacity after acid treatment [183; 193].  
Similarly, the biosorption efficiency of Fe, Zn, and Ni(II) was significantly improved by _Phanerohate chrysosporium_ and _Aspergillus japonicus_ at neutral to alkaline pH (7.0-9.0) [194; 195]. At pH 3.0, Cu, Ni, and Zn biosorption are negligible. This might be due to _Aspergillus niger_'s cations and hydronium ions competing for binding sites [196].  
Treatment of fungal biomass with FeSO4 and FeCl3 improved the biosorption ability of As(V) by _Aspergillus fumigatus_[193].  
Metalloids and metals can be biotransformed by altering the microenvironment via catalysis, oxidation, and reducing mobility and metal solubility [185]. Methylation and decarboxylation are also involved in biotransformation, and these reactions can volatilise metals and thus reduce their toxicity. In addition to cytoplasmic vesicles and vacuoles, cytoplasmic vesicles and vacuoles can transport metals to the mycelium and plant symbionts of fungi. The biotransformation of numerous aromatic hydrocarbons by yeast, including long-chain phenyl alkanes, chlorinated phenols, ethylated benzene, dibenzofurans, ethers and their halogenated derivatives, dioxins, and polycyclic aromatic hydrocarbons, has been extensively reported [197]. However, it should be emphasised that many of these xenobiotics can be biotransformed into various compounds with unknown properties. Exploring the resulting products' risk assessments and biotransformation mechanisms is necessary to minimise the environmental impact. It has been observed that wood rot fungi can biotransform cadmium into cadmium oxalate trihydrate, zinc sulfate into zinc oxalate, copper sulfate into copper oxalate, and lead nitrate into lead oxalate [198].  
A pseudo-ion exchange process, also called biosorption, involves exchanging metal ions for counterions in biomass or resin. Generally, filamentous fungi have a greater capacity to adsorb heavy metals, and Aquatic fungi have also been shown to accumulate heavy metals. [PERSON] et al. [199] described the uptake of metals, and a hypothesis was made about the mechanisms of bioaccumulation in fungi. It was discovered that the marine fungi _Corollospora lacera_ and _Monodictys pelagic_ accumulate lead and cadmium extracellularly in their mycelia [200]. Several external factors (such as the type of metal, functional site, and ionic form in solution) and an exothermic tendency are involved in biosorption. Other variables such as type of biomass preparation, biomass concentration, temperature, initial metal ion concentration and metal properties, pH, and ion concentrations of other interfering species are critical in determining the extent of biosorption. Biosorption and recovery can be enhanced by a magnetic field-induced stirring [201].