92

Bioremediation for Sustainable Environmental Cleanup

and Kumar 2019). Ligninolytic fungi are proficient in synthesizing extracellular enzymes viz, LiP

and MnP which are utilized in PAHs mineralization, apart from intracellular enzymes. Ligninolytic

enzymes, break down such contaminants and produce free radicals. These free radicals then oxidize

various aromatic molecules, resulting in different quinones (Kadri et al. 2017). Non-ligninolytic

fungi are usually inefficient in extracellular enzyme production and intracellular enzymes such

as CYP450 play a significant role in PAHs degradation (Dutta and Laha 2022). The predominant

fungal phyla that are highly considered as a potential bioagent for PAHs remediation belong to

Ascomycota (non-ligninolytic fungi), followed by Basidiomycota (ligninolytic fungi) and the least

by Zygomycota that is categorized under the non-ligninolytic members (Banerjee and Mandal 2020,

Passarini et al. 2011). In this, diversified fungal agents which have the potential to eliminate the

PAHs from contaminated soil and their mode of action have been documented in (Table 6.2) and

from this analysis a similar pattern of dominant fungal phyla was observed, where Ascomycota

appeared as the most dominant member (64%) followed by Basidiomycota (33%) and Zygomycota

(3%), respectively (Figure 6.3).

Figure 6.3. Diversity of fungal representatives involved in PAHs biodegradation.

6.3.1.1 PAHs Degradation by Ligninolytic Fungi

In the last couple of decades, ligninolytic fungi have been thoroughly investigated for their PAHs

remediating potentialities. Phenomenally they produce extracellular enzymes such as laccase

and peroxidases which play the most crucial role in PAHs mineralization (Kadri et al. 2017). In

this aspect, most extracellular ligninolytic enzymes-producing fungi belong to Basidiomycota

(Winquist et al. 2014). White-Rot Fungi (WRF) also play a crucial role in PAHs degradation, e.g.,

Bjerkandera adusta, Pleurotus ostreatus, Phanerochaete chrysosporium, Trametes versicolor, Irpex

lacteus (Bezalel et al. 1996, Vyas et al. 1994, Field et al. 1992). Some investigations show that