• Inhibition of Growth: High concentrations of cadmium in the soil can inhibit plant growth and development. It interferes with essential physiological processes, such as cell division, nutrient uptake, and photosynthesis, leading to stunted growth and reduced plant biomass.

  • Nutrient Imbalance: Cadmium can disrupt the uptake and transport of essential nutrients like calcium, iron, zinc, and magnesium in plants. This can lead to nutrient imbalances, deficiency symptoms, and impaired metabolic functions.

  • Oxidative Stress: Cadmium induces oxidative stress in plants by promoting the production of reactive oxygen species (ROS).

  • Chlorosis: Cadmium toxicity can cause chlorosis, a condition characterized by yellowing of leaves due to a decrease in chlorophyll production.

  • Disruption of Photosynthesis: Cadmium interferes with the photosynthetic process in plants, reducing their ability to convert light energy into chemical energy.

  • Altered Hormonal Regulation: Cadmium can disrupt plant hormonal balance, affecting processes like root growth, flowering, and fruit development. This can further impact overall plant growth and reproductive success.

  • Reduced Seed Germination and Viability: Cadmium exposure can reduce seed germination rates and seedling vigor. This can result in poor crop establishment and lower crop yields in agricultural settings.

  • Phanerochaete chrysosporium

    Phanerochaete chrysosporium

  • Lentinus edodes

    Lentinus edodes

  • Auricularia polytricha

    Auricularia polytricha

  • Sell it.

Cell surface binding sites:

  • carboxyl (–COOH)

  • thiol (–SH)

  • hydroxide (–OH)

  • phosphate (PO43−)

  • amide (–NH2)

  • Carbonyl (C=O)

Limitations:

  • Low-performing metal ions in multi-metal consortiums

  • Low mobility for soil treatment

  • Limited by biotic condition

Cadmium tolerance antioxidants & enzymes:

  • Superoxide dismutase (SOD)

  • Catalase (CAT)

  • Glutathione reductase 

  • Proline

  • Glutathione peroxidase

Bioremediation processes:

  • Adsorption

  • Intracellular accumulation

  • complexation

  • Chelation

In bioremediation studies, cadmium oxalate crystals have been identified on the mycelium surface. These findings implicate oxalic acid which is produced by certain fungal strains in the bioleaching process. Additionally, studies have noted the upregulation and increased activities of antioxidant enzymes in the presence of cadmium which points towards a positive correlation between enzyme activity and cadmium tolerance. Cadmium stress on fungal species results in the overproduction of free radicals, it is therefore suggested that antioxidant enzymes are deployed in order of detoxifying excess free radicals. 

The removal of Cadmium ions predominantly relies on adsorption. The efficiency of adsorption depends on the availability of binding sites on the biomass surface. For this reason, sorbent designs that increase the porosity, and therefore the surface area, of the biomass tend to yield increased removal rates, reflecting improved binding potential.

The removal of Cd ions from aqueous solutions by fungal biomass has been tested in a number of lab-scale experiments alongside other heavy metal ions. The complex operations of manufacturing mean Industrial wastewaters typically contain an assortment of heavy metal ions. It is therefore necessary to test the functional efficiency of fungal strains in multi-metal solutions. Tests of this nature regularly identify adversarial competition between metal ions resulting in imbalanced sorption rates. The metal ions compete for binding sites on the mycelium surface so that certain groupings of metal ions (Pd and Cu) can prove complementary, increasing the overall adsorption of both members, while others (Cu and Cd) demonstrate incompatibility, with the strongest of the pair inhibiting binding in the other.

Fungal Strain Capacity pH Time Biomass Removal Type Method Reference
Aspergillus
foetidus		 79-100% 5 96h Viable Biosorption
Bioleaching
Complexation		 Liquid Media Chakraborty et al
2014
Aspergillus
fumigatus		 98% 5 90m Viable Adsorption yeast peptone
glucose (YPG)
 Al-Garni et al
2009
Aspergillus niger 96.98% 4.75 6h Viable Biosorption Boiled in NaOH   Júnior et al 2003
Auricularia polytricha 88.97% 5-6 30m Immobilised Sorption Powdered
mycelium sorbent		 Zhan et al 2011
Fusarium sp 70% 5 48h viable/
immobilised		 Intracellular
accumulation		 (PT) NaOH
composted material		 Vargas-García
et al 2012
Lentinus edodes 274.3mg/g 7 120m Immobilised Adsorption Pellets G.Bayramoglu &
Y.Arica 2008
Mucour rouxii N/A 6 6h Immobilised Biosorption Batch Experiments Yan et al 2003
Pleurotus ostreatus 85% 4.5 10d Viable Accumulation
Adsorption		 Soil remediation Li et al 2017
Penicillium canescens 102.7 mg/g 5 4h Viable Adsorption Batch Experiments Say et a 2003
Penicillium
chrysogenum		 99.7% 6.5 120m Immobilised Adsorption hybrid cryogel discs Bayrak et al 2023
Aspergillus ustus 84% 6 240m Immobilised Biosorption Batch Experiments Alothman et al 2019
Penicillium
chrysogenum		 91% 5 120m Immobilised Biosorption Batch Experiments Alothman et al 2019
Penicillium
chrysogenum		 52.0% 7 30m Immobilised Biosorption Loofa sponge Ali et al 2021
Phanerochaete
chrysosporium		 99.71% N/A 7d Viable Adsorption
Accumulation		 Batch Experiments Sharma et al 2022
Phanerochaete
chrysosporium		 95% 5 180m Immobilised Biosorption (white rot fungus) -
modified bentonite		 Kocaoba et al 2021
Phlebia brevispora 98% N/A 7d Viable Adsorption
Accumulation		 Batch Experiments Sharma et al 2022
Rhizopus cohnii 40.5 mg/g 4.5. 2h Viable Biosorption Batch Experiments Ming et al 2010

  • Ali, E.A.M., Sayed, M.A., Abdel-Rahman, T.M.A. and Hussein, R. (2021). Fungal remediation of Cd(II) from wastewater using immobilization techniques. RSC Advances, [online] 11(8), pp.4853–4863. doi:https://doi.org/10.1039/D0RA08578B.

    Alothman, Z.A., Bahkali, A.H., Khiyami, M.A., Alfadul, S.M., Wabaidur, S.M., Alam, M. and Alfarhan, B.Z. (2019). Low cost biosorbents from fungi for heavy metals removal from wastewater. Separation Science and Technology, 55(10), pp.1766–1775. doi:https://doi.org/10.1080/01496395.2019.1608242.

    Barros Júnior, L.M., Macedo, G.R., Duarte, M.M.L., Silva, E.P. and Lobato, A.K.C.L. (2003). Biosorption of cadmium using the fungus Aspergillus niger. Brazilian Journal of Chemical Engineering, 20(3), pp.229–239. doi:https://doi.org/10.1590/s0104-66322003000300003.

    Chakraborty, S., Mukherjee, A., Khuda-Bukhsh, A.R. and Das, T.K. (2014). Cadmium-induced oxidative stress tolerance in cadmium resistant Aspergillus foetidus: its possible role in cadmium bioremediation. Ecotoxicology and Environmental Safety, 106, pp.46–53. doi:https://doi.org/10.1016/j.ecoenv.2014.04.007.

    Gülşen Bayrak, Neslihan İdil and Işık Perçin (2023). Penicillium chrysogenum-loaded hybrid cryogel discs for heavy metal removal. 77(7), pp.3921–3936. doi:https://doi.org/10.1007/s11696-023-02752-0.

    Kocaoba, S., Parlak, M.D. & Arisoy, M. The use of Phanerochaete chrysosporium for modification of bentonite for preconcentration and determination of heavy metals. J Anal Sci Technol 12, 24 (2021). https://doi.org/10.1186/s40543-021-00277-3

    Li, X., Wang, Y., Pan, Y., Yu, H., Zhang, X., Shen, Y., Jiao, S., Wu, K., La, G., Yuan, Y. and Zhang, S. (2017). Mechanisms of Cd and Cr removal and tolerance by macrofungus Pleurotus ostreatus HAU-2. Journal of Hazardous Materials, 330, pp.1–8. doi:https://doi.org/10.1016/j.jhazmat.2017.01.047.

    Luo, J., Xiao, X. and Luo, sheng-lian (2010). Biosorption of cadmium(II) from aqueous solutions by industrial fungus Rhizopus cohnii. Transactions of Nonferrous Metals Society of China, [online] 20(6), pp.1104–1111. doi:https://doi.org/10.1016/S1003-6326(09)60264-8.

    M.C. Vargas-García, Lopez, M.A., Suárez-Estrella, F. and Joaquín Melgarejo Moreno (2012). Compost as a source of microbial isolates for the bioremediation of heavy metals: In vitro selection. Science of The Total Environment, 431, pp.62–67. doi:https://doi.org/10.1016/j.scitotenv.2012.05.026.

    Say, R., Yilmaz, N. and Denizli, A. (2003). Removal of Heavy Metal Ions Using the Fungus Penicillium Canescens. Adsorption Science & Technology, 21(7), pp.643–650. doi:https://doi.org/10.1260/026361703772776420.

    Sharma, K.R., Giri, R. and Sharma, R.K. (2022). Efficient bioremediation of metal containing industrial wastewater using white rot fungi. International Journal of Environmental Science and Technology. doi:https://doi.org/10.1007/s13762-022-03914-5.

    TY - JOUR AU - Al-Garni, Saleh AU - Ghanem, khaled AU - Bahobail, Abdulaziz PY - 2009/10/01 SP - 4163 EP - 4172 T1 - Biosorption characteristics of Aspergillus fumigatus in removal of cadmium from an aqueous solution VL - 8 JO - African Journal of Biotechnology ER -

    TY - JOUR AU - Bayramoglu, Gulay AU - Arica, Yakup PY - 2008/09/15 SP - 133 EP - 140 T1 - Removal of heavy mercury(II), cadmium(II) and zinc(II) metal ions by live and heat inactivated Lentinus edodes pellets VL - 143 DO - 10.1016/j.cej.2008.01.002 JO - Chemical Engineering Journal ER -

    Yan, G. and Viraraghavan, T. (2003). Heavy-metal removal from aqueous solution by fungus Mucor rouxii. Water Research, 37(18), pp.4486–4496. doi:https://doi.org/10.1016/s0043-1354(03)00409-3.

    Zhang, D., Wang, J., Zeng, X. and Jerzy Falandysz (2011). Competitive sorption efficiency studies of Cd(II), Cu(II) and Pb(II) by powdered mycelium of Cloud Ear FungusAuricularia polytricha. 46(14), pp.1776–1782. doi:https://doi.org/10.1080/10934529.2011.625300.

Example of disparate sorption across a multi-metal consortium (Rama Roa et al 2005)

variables affecting efficiency:

  • Temperature

  • Biomass dose

  • Multi-metal consortium

  • pH

  • Contact time

  • Heavy metal tolerance

  • Growth medium

  • Pretreatment

  • Viable or immobilized biomass

  • Metal Ion concentration

Types of application:

  • loofa sponge

  • alginate beads

  • hydrogel discs

  • Living biomass

  • Immobilized powdered biomass

  • fungi-microalgae symbiotic system(FMSS)

Fungal processes determining the removability of heavy metals include:

  • Biosorption: Metal ion adsorption to fungal cell surfaces by physio-chemical mechanisms.

  • Bioleaching: The mobilization of heavy metals via methylation reactions or the excretion of organic acids.

  • Biomineralization: Immobilisation and detoxification of heavy metals through the formation of insoluble sulfides or polymeric complexes.

  • Intracellular accumulation: accumulation of heavy metal ions within the fungal cell membrane

  • Enzymatic transformation: Enzyme-catalyzed transformation by redox processes.