Fungal Strategies for the Remediation of Polycyclic Aromatic Hydrocarbons 99

Figure 6.6. Bioremediation of anthracene by P. chrysosporium (Pozdnyakova 2012).

6.3.1.1.2.3 Versatile peroxidase

Versatile Peroxidases (VP) belong to the peroxidase family and are glycoproteins in nature which

consist of 11–12 α-helices, a pair of Ca²⁺ binding sites, four disulfide bonds, a haem pocket and

an Mn²⁺ binding site (Perez-Boada et al. 2005). It can be used in bioremediation of both aromatic

and aliphatic contaminants. It involves the oxidative reaction of Mn²⁺, aromatic compounds and

methoxybenzenes like LiP and MnP. VP is more efficient than other peroxidases as it exhibits various

substrate specificities and can function even in manganese-deficient conditions. This enables VP to

be a potent biocatalyst and opens new doors in biotechnological techniques for the bioremediation

of organic pollutants (Ruiz-Duenas et al. 2007). Examples of WRF which produced VP enzyme are

B. adusta and P. eryngii (Naghdi et al. 2018). Additionally, a significant amount of PAHs degradation

of ANTH, PYR and B(a)P was documented from the B. adusta by its VP enzymatic appliances

(Wang et al. 2003). Another example of VP-mediated PHE degradation was also reported from a

member of WRF T. versicolor (Collins et al. 1996). Further, Bogan et al. (1996) observed that the

utmost FLR degradation was achieved by a WRF P. chrysosporium. CHY remediation was also

documented from the P. ostreatus with its VP activity (Nikiforova et al. 2010). P. ostreatus was also

reported for its PYR degrading capability through VP producing ability (Pozdnyakova et al. 2010).

Multiple PAHs remediating potentiality was also achieved by the VP producing WRF Nematoloma

frowardii (Sack et al. 1997).

6.3.1.2 PAHs Degradation by Non-ligninolytic Fungi

Ligninolytic fungi primarily grow on woody substances, which partially restrict their growth in

soil. Hence their potentiality for PAHs biotransformation in the soil condition is quite ambiguous

(Steffen et al. 2002). Therefore, non-ligninolytic fungi with intracellular enzymes, especially

CYP450, can metabolize PAHs along with only substrate. Detoxification of organic pollutants by

non-ligninolytic fungi is a predominant characteristic of their ability to pass through the cell wall

where cell membrane-mediated enzymes such as cytochrome P450 monooxygenase and hydrolase

operate the mineralization process (Marco-Urrea et al. 2015). The enzymatic mechanism involves the

catalysis and hydrophobic (water-insoluble) PAHs transformed into less-toxic partially hydrophilic

(water-soluble) intermediates via the epoxide ring opening mechanism, which cleaves the aromatic

structure of PAHs and leads to the formation of arene oxide. This can be further transformed into

phenol and trans-dihyrodiols, which are catalyzed by the hydrolase enzyme (Sutherland 1992).

Chrysosporium pannorum, C. elegans and A. niger are among such examples, involved in PAH

degradation with such a mechanism. The biotransformation of PAHs by non-ligninolytic fungi depicts

a typical sequential pattern having two significant phases. The first phase causes the production of

dihydroxy-quinone and dihydrodiol-derivatives, which further conjugates in the second phase with

O-glucoside, O-sulfate, O-glucuronide, O-methyl and O-xyloside. These metabolites are water­