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Bioremediation for Sustainable Environmental Cleanup

the unsolvable form of metal (Rudakiya et al. 2019). The following kinds of bioremediations are

used to eliminate toxic heavy metals, metalloids and non-metals from different areas:

13.3.1 Bacterial remediation

13.3.2 Fungal remediation

13.3.3 Algal remediation

13.3.4 Phyto remediation

13.3.1 Bacterial Bioremediation

There are different mechanisms used by bacteria to remediate or eliminate metals (Rudakiya and

Pawar 2017). Bacteria use the processes of metal binding, biosorption, biotransformation and

biosorption to eradicate metals from aquatic environments (Rudakiya 2018). The process in which

metals are oxidized and reduced to change into nontoxic forms is called biotransformation. The

following processes occur during biotransformation outside the cell:

• Reduction

• Oxidation

• Methylation.

• Dealkylation

Bacteria consist of carbohydrates, protein and fatty acids. These components are very essential

for the binding of metals. Enzymes can also be used for the transformation of metals. For example,

chromate reductase. It forms a species of metals that are not usually soluble (Rudakiya et al. 2020).

13.3.2 Fungal Bioremediation

The fungi are especially important organisms to treat metalloids and metals based on different

properties like biochemical, ecological and morphological (Rudakiya and Gupte 2017). Fungi can

be used to treat metals throughout the various phases of their life cycle through different mechanisms

(Baldrian 2003). These components of the cell wall contain various functional groups viz. hydroxyl,

phosphate, carboxyl and amine. They are involved in the process of ‘metal chelation’ (Couto et al.

2004).

Many other microorganisms make different substances like Extracellular Polymeric Substances

(EPS) in the environment where they exist (Guibaud et al. 2005). These substances can be used in

binding, reduction of heavy metals and tolerance limits. EPS are anionic and acidic in nature. The

anionic characteristics of EPS transmit “electrostatic interaction” with heavy metals however, the

acidic property of Extracellular Polymeric Substances is due to different functional groups such as

amino acids, phenolic, hydroxyl, carboxyl and uronic acids. These groups interact with metal ions

that have a positive charge (Gutnick and Bach 2000). Heavy metals like Cu, Pb and Cd have been

separated by A. niger (Kapoor et al. 1999).

Interaction among metals and fungi: Fungi can be used for the bioremediation of heavy metals

due to their various properties such as rapid growth, easily culturable due to their small reproduction

cycle and can be modified both genetically and morphologically (Dhankhar and Hooda 2011).

The elimination of toxic substances by fungi is called mycoremediation. Fungi can use various

mechanisms for heavy metal bioremediation, especially the biosorption process. The dead and living

cells of fungi can be used for fungal biosorption. The dead cells of fungi have a higher capacity to

remove heavy metals (Volesky 2007).

Fungi can use two mechanisms for the removal of metals (Veglio and Beolchini 1997). The

first method is the primary method which includes the binding of heavy metals to the outer surface