Fungal Strategies for the Remediation of Polycyclic Aromatic Hydrocarbons 101

compounds made up of amphiphilic domains consisting of both a hydrophilic (polar) head as

well as hydrophobic (non-polar) tail, which bind with the complementary polarity compounds

by lowering the surface tension and interface pressure of solutions (John et al. 2021, Kour

et al. 2021). Synthesis of biosurfactants by various microbes enhances the solubility and causes

ease to mineralize non-polar compounds such as PAHs via mobilization, micelle formation and

solubilization, that accelerate their bio-accessibility to the microbial community in the environment

(Imam et al. 2022, Pourfadakari et al. 2021, Maia et al. 2019, Dell’Anno et al. 2018). Based on

the molecular structure, biosurfactants are categorized into two types (1) Low-molecular-weight

biosurfactants and (2) High-molecular weight biosurfactants. LMW-Biosurfactants are primarily

composed of lipopeptides, phospholipids, lipoproteins, fatty acids, glycolipids and neutral lipids,

which enhance the surface area of organic pollutants and accelerate their bioavailability in the

microbial cleanup process (Henkel and Hausmann 2019, Yuliani et al. 2018). HMW-Biosurfactants

include polysaccharides, lipopolysaccharides, proteins and lipoproteins which in turn can readily

interact with various surfaces and act as an emulsifier of pollutants like PAHs (Fenibo et al. 2019,

McClements and Gumus 2016).

Phellinus sp. and Polyporus sulphureus belong to the Basidiomycota phylum and are capable

of mineralizing HWM-PAHs by producing a high amount of biosurfactant. Biosurfactants secreted

by Phellinus sp. and P. sulphureus were achieved to remediate the oil spillage by the production

of biosurfactants with dry weight 3.4 g/L and 2.6 g/L where PAHs degradation potentiality were

evidenced as the emulsion index were 122 and 106%, respectively (Arun and Eyini 2011). Wang

et al. (2008) suggested that the biosurfactant rhamnolipid enhanced the functionality of extracellular

enzymes such as LiP and MnP synthesized by P. chrysosporium and laccase secreted by

P. simplicissimum. Additionally, P. ostreatus can degrade both LMW-PAHs as well as HMW-PAHs

facilitated with an emulsifier agent which also escalates the action of VP (Nikiforova et al. 2009).

6.5 Biochar Immobilized Fungal Administration

Biochar is a pyrolyzed carbonaceous substance that can be produced from biomass (woody waste)

through thermal treatment under anaerobic conditions. Biochar is environmentally friendly, of

low cost and a sustainable administrator, its features are primarily used for organic and inorganic

pollutant remediation. Biochar that has been totally carbonized and generated at temperatures

exceeding 500°C acts as a superior adsorbent for organic contaminants because of its vast surface

area, microporosity, hydrophobicity, C-N ratio and high pH value (Jatav et al. 2021). Features

that make biochar a promising strategy for the bioremediation of organic hydrocarbons like PAHs

are (i). Biochar can readily change its surface volume and quantity of oxygen molecules having

functional groups, (ii). Affinity towards organic hydrocarbon through the π-π bond, hydrogen bond

and covalent bond, (iii). Reduction in the bioavailability and solubility of organic pollutants such

as PAHs (cause immobilization of PAHs), and (iv). Microbial augmentation and phytoremediation

assisted with biochar enhancing its pollutant remediation efficiency by many folds. García-Delgado

et al. (2015) investigated that biochar immobilized fungal agent with P. ostreatus exhibited 55,

40, 31 and 89% biodegradation of HMW-PAHs like B(a)P, B(a)A, CHRY and DBA, respectively.

Biochar immobilized with P. chrysosporium hyphae was able to accelerate the rate of abatement of

PAHs like PHE with more than 90% removal efficiency (Zhang et al. 2022).

6.6 Utilization of Rhizospheric and Endophytic Fungi

Numerous documents have been recorded describing the plant uptake and bioaccumulation of

organic hydrocarbons (PAHs) from the soil (Anderson et al. 1993). Rhizospheric and endophytic

microbes play a critical part in the removal of PAHs from the soil, exhibiting an eco-friendly, low-

cost and sustainable approach. The rhizospheric microorganisms reside in the vicinity of plant roots

and get nourished by the root exudates, whereas endophytic microorganisms are the residents of

plant internal tissue. Arbuscular mycorrhizal fungi symbiotically associated with most herbaceous