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Bioremediation for Sustainable Environmental Cleanup

In regard to microbial PAHs bioremediating representatives, bacteria are extensively

documented as organisms being used for bioremediation practices due to their biochemical as

well as genetic flexibility (Banerjee et al. 2017). However recently, mycoremediation has been

acknowledged more (Conejo-Saucedo et al. 2019, Treu and Falandysz 2017). Fungi are the most

suitable agent for PAHs biotransformation and are preferred above bacteria, algae or plants for

various reasons. The association of the mycelia meshwork of fungi is capable of penetrating soils

and accessing the soil void space. In comparison to unicellular bacteria, the fungal mycelium act

as a unit, proliferates like a net or mesh-like structure or formulates rhizomorphs around hazardous

materials and can propagate in an indeterminate way until the resources are accessible (Banerjee

and Mandal 2020). In addition, the key equipment of fungi is that they habitually produce a greater

number of bioactive molecules, especially the extracellular enzymes which are accountable for the

degradation of macromolecules like PAHs (Mougin et al. 2009, Ritz and Young 2004, Osono et al.

2003). Further, ligninolytic fungi gained great attention due to their enzymatic appliances, which

are not only associated with lignin degradation but also employed during the mycoremediation

practices in PAHs contaminated environment (Gadd and Gadd 2001). Apart from these enzymatic

approaches, this chapter is also focused on the diverse fungal strategies such as the production

of biosurfactants, biochar immobilized mycoremediation and the contribution of rhizospheric and

endophytic fungi to remediate the PAHs.

6.2 Bibliographic Analysis

In this bibliographic study, a total of 1641 articles have been extracted from the Web of Science with

the combinations of keywords such as PAHs, biodegradation, mycoremediation, white-rot fungi,

enzyme, peroxidase, biochar, biosurfactant and so on, which are relevant to construct this chapter.

All the keywords have been analyzed with the help of VOS viewer software. Here the co-occurrence

keywords have been chosen up to 17, and a fractionalization network of linkage map was constructed

displaying the frequently searched keywords in those articles, which is illustrated in Figure 6.1.

A total of five clusters were found in this keyword co-occurrence analysis. Each cluster and co­

occurrence keywords are represented by specific size and color, and the straight lines connecting

them display the anecdote links. From this network analysis of the keywords, it was discovered

that these articles primarily addressed the following five clusters or aspects: (1) different PAHs and

their mycoremediation strategies, i.e., biosorption, biosurfactant, biochar, fungal consortium, etc.

(red cluster) (2) fungal enzymes responsible for PAHs degradation like laccase, lignin peroxidase,

manganese peroxidase, etc. (green cluster) (3) fungal members with PAHs degrading ligninolytic

enzymatic activity (yellow cluster) (4) fungal metabolism in the biotransformation of the PAHs (sky

blue cluster) (5) mycoremediation with enzymatic and surfactant based approaches (purple cluster).

This keywords-oriented text mining study explored the fungal members and their strategies involved

in the remediation of PAHs. At the same time, it is also demonstrated that the rhizospheric as well

as arbuscular mycorrhizal fungi are the key appliances found in support of the mycoremediation

processes. Therefore, the connecting bond between these diverse fungal members and their strategies

assisted in the construction of this current study.

6.3 Fungal Strategies mediated PAHs Remediation

Due to the high population growth and excess usage of petroleum resources, the number of PAHs

released from street transportation, industrial, commercial and residential origin are increasing

exponentially day by day. Additionally, in urban areas spontaneous contamination is occurring

from the fossil fuel industries, motor vehicles, electricity generation plants, etc. (Figure 6.2)

(Ball and Truskewycz 2013). Further, the structural rigidity and human health impacts of PAHs

(Table 6.1) gained the attention of several environmental specialists. Therefore, remediating the

PAHs contaminated areas is indeed needed to restore the ecological health to a regular condition as

this hazardous pollution is detrimental to ecological damages. In this context, bioremediation appears