Fungal Strategies for the Remediation of Polycyclic Aromatic Hydrocarbons 97

Figure 6.5. Ligninolytic and non-ligninolytic fungal mechanism responsible for PAHs degradation.

members viz, Bacillus subtilis, Azospirillum lipoferum, Sinorhizobium meliloti and Streptomyces

lavendulae, whereas in the fungal system, intracellular and extracellular laccases are documented for

a different type of PAHs remediation (Banerjee and Mandal 2020, Pawlik et al. 2016). Several reports

have demonstrated that fungi utilize PAHs via the production of an extracellular enzyme like laccases

resulting in PAHs degradation with CO2 as a byproduct. A significant amount of PAHs removal

capability by laccase-producing WRF Anthracophyllum discolor was documented with 62% of PHE,

73% of anthracene (ANTH), 54% of fluoranthene (FLU), 60% of PYR and 75% of B(a)P degrading

potentiality (Acevedo et al. 2011). In a recent study, a WRF strain Trametes versicolor exhibited

excellent remediational attributes like 81.0% CHY and 91.0% B(a)P degradation with

37.8 Ug^–1 laccase producing potentiality (Vipotnik et al. 2022). In addition, another report of a WRF

Pycnoporus sanguineus with 2516.7 UL^–1 of laccase production ability displayed 90.1% B(a)A and

45.6% PHE degrading capacity (Li et al. 2018). Further, laccase produced by T. versicolor was also

found to be able to remediate contaminants such as acenaphthene (ACE), B(b)F and PYR (Noman

et al. 2019). In this regard, Punnapayak et al. (2009) reported that laccase-producing WRF

Ganoderma lucidum can also efficiently degrade ACE and acenaphthylene.

6.3.1.1.2 Peroxidases

Peroxidases are the glycosylated extracellular enzyme that requires hydrogen peroxide to catalyze

lignin and organopollutant compounds like PAHs (Thurston 1994). The peroxidases are classified

into two categories based on their substrate interaction—MnP which is the most effective reducing

substrate and LiP which catalyzes both non-aromatic and aromatic compounds (Ten Have and

Teunissen 2001). Hydrogen peroxide (H2O2) is essential for the activation of the MnP and LiP are

synthesized by fungal producers during their metabolic processes. In such metabolic processes,

H2O2 acts as an oxidizing agent that oxidizes the PAHs and transforms them into a substrate