Bioremediation: A Sustainable Approach for Environmental Cleanup 7

Table 1.1. Polycyclic Aromatic Hydrocarbons (PAHs) degrading microorganisms.

PAHs

Microorganism

References

Phenanthrene

Arabidopsis thaliana ATCG5600

Hernández-Vega et al. 2017

Pyrene

Achromobacter xylosxidans PY4

Nazifa et al. 2018

Benzo (a) pyrene

Serratia marcescens

Kotoky and Pandey 2020

Phenanthrene, Pyrene, fluoranthene

Pseudomonas aeruginosa,Ralstonia sp.

Sangkharak et al. 2020

Phenanthrene

Bacillus thuringiensis, Pleusotus cornucopiae,

Pseudomonas

Jiang et al. 2015

Pyrene

Roseobacter clade

Zhou et al. 2020

Benzo (a) pyrene

Aspergillus nidulans

Ostrem Loss et al. 2019

Benzo (a) pyrene

Lasiodiplodia theobromae

Cao et al. 2020

Benzo (a) pyrene

Megasporoporia sp. S47

De Lima Souza et al. 2016

Phenanthrene

Coriolopsis byrsinaRyvarden strain APC5

Agrawal et al. 2021

aquatic species, Benzo(a)Pyrene (BaP), is known for its mutagenic, carcinogenic and teratogenic

characteristics (IARC 1983, Juhasz and Naidu 2000, Jennings 2012). In literature, ligninolytic and

non-ligninolytic strains of fungi with the ability to breakdown PAH have been documented. The

degradation of BaP by white-rot fungus has been the subject of recent research (Hadibarataa and

Kristanti 2012, Bhattacharya et al. 2014). White rot fungi such as Phanerochaete chrysosporium,

Trametes versicolor, Cirnipellis stipitaria and Pleurotus ostreatus can breakdown most PAHs

efficiently as a carbon source. The white rot fungus Phanerochaete chrysosporium has a remarkable

ability to degrade and/or mineralize high-molecular-weight PAHs, and its genome has around

150 Polymorphic Cytochrome P450 Enzymes (CYPs) (Yadav et al. 2006) and has the ability

to oxidize BaP to 3-hydroxybenzo[a]pyrene (Syed et al. 2010). These CYPs were inducible by

naphthalene, phenanthrene, pyrene and BaP. Aspergillus, the most prevalent species of soil-dwelling

fungi, may metabolize some PAHs and is frequently found in contaminated areas (Cerniglia and

Sutherland 2010).

1.5.2 Bioremediation of Polychlorinated Biphenyls (PCBs)

Polychlorinated biphenyls (PCBs) are combinations of 209 types of synthetic organic chemicals

called congeners (US EPA 2000). This substantial number of different chemical forms results

from the binding of 110 chlorine atoms to the carbon atoms of the biphenyl core. The level of

chlorination has a significant impact on the physical and chemical characteristics of PCBs. As the

level of chlorination rises, PCBs become more viscous and waxy, while their solubility in water

tends to decrease. The Agency for Toxic Substances and Disease Registry (ATSDR) states that

PCBs are “oily liquids or solids, colourless to light yellow, and have no recognized odour”. The

unusual properties of PCBs include high thermal stability, chemical inertness, non-flammability

and high electrical resistivity, that are relatively used in hydraulic fluids, capacitor dielectrics and

electrical transformers. Other potential sources of PCBs include leaks, spills and slow release from

PCB-contaminated areas (Van Aken and Bhalla 2011). PCBs are hazardous xenobiotics, mostly

found in soils and sediments and are widely dispersed in the environment. It is well known that

biphenyl dioxygenase is essential for the breakdown of PCBs. Due to the presence of a large number

of congeners; efficient microbial breakdown of PCBs requires a number of metabolic processes.

The microorganisms responsible for PCB transformation are unable to grow on PCBs as the only

carbon source (Boyle et al. 1992) and require a co-substrate for microbial growth and degradation

activity, demonstrating that PCB degradation occurs predominantly via co-metabolism. PCBs are

hazardous chemicals that can affect hormones and cause cancer. As a result, PCB poisoning in the

environment is becoming increasingly problematic and is of great concern (Seeger et al. 2010).

Several approaches have been proposed for PCB degradation in the environment. The study is