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electric current was applied for the enhancement of phenol degradation. Basically P. putida and

other microorganisms degrade via meta and para cleavage pathways influenced by the concentration,

temperature and biogenic factors. Most of the redox biochemical reaction are facilitated by applying

constant voltage across the bioreactor along with microbial community (Bandhyopadhyay et al.

1999).

8.3.7 Chlorpyrifos and Carbofuran

Carbofuran is a chemical that is used to kill insects and corn rootworm (Tomasek and Karns 1989). As

a nitrogen source, Achromobacter species WM111 can hydrolyze N-methylcarbamate (Karns et al.

1986). The mcd gene encodes N-methylcarbamate hydrolase, which aids in degradation. This gene

has been cloned and is being expressed in soil bacteria (Tomasek and Karns, 1989). Chlorpyrifos

and carbofuran were also co-degraded in P. putida KT2440 by scarless counter-selectable marker

heterologous expression of CP/carbofuran hydrolase genes (Gong et al. 2016). Compared to the

CP/carbofuran, the digestion products’ toxic effects were significantly diminished. Interestingly,

CP/carbofuran were used as the only carbon source by the mutant for the growth and degradation

rate was also found high compared to uninoculated soil.

8.3.8 Beta-cypermethrin

Beta-cypermethrin (β-CY) is a significant pyrethroid pesticide (Xiao et al. 2015). It is a toxin that

affects the reproductive, immune, nervous and genetic systems. (Jin et al. 2011, McKinlay et al.

2008, Schettgen et al. 2002). The pesticide can be co-metabolized and degraded by Aspergillus

niger YAT, Bacillus licheniformis B-1, Brevibacterium aureum and Brevibacillus parabrevis

BCP-09 (Tran et al. 2013, Chen et al. 2013, Deng et al. 2015, Tang et al. 2018). However, soil

degradation was limited. As a result, Loh and Wang (1997) discovered that P. putida ATCC 49451

can degrade 4-chlorophenol. The process was accelerated in the presence of sodium glutamate. But

this process was hampered by glucose (Zhao et al. 2019a,b).

Lindane or c-hexachlorocyclohexane, c-HCH is a highly toxic pesticide that cause Anabaena

to lose protective chaperons, inhibit photosynthesis and fix nitrogen (Bueno et al. 2004, Singh

1973, Nawab et al. 2003). In Sphingomonas paucimobilis B90, the linA2 gene encodes c-HCH

dehydrochlorinase, which degrades the pesticide. Similarly, the pesticide is degraded by the linA

gene in P. paucimobilis UT26 (Adhya et al. 1996, Nagata et al. 1997). In the presence of an inducible

promoter PpsbA1, these genes were knocked in and overexpressed in Anabaena. In 12 hr, this strain

could degrade 10 ppm of lindane isomers (Chaurasia et al. 2013).

8.3.9 s-Triazines

s-Triazines are a class of herbicides used to control weeds, such as atrazine. Pseudomonas sp., strain

A uses ozone to oxidize atrazine, and the ozonated products are used by soil microbes (Karns et

al. 1987, Kearney et al. 1988). S-triazine is also used as the only nitrogen source by Pseudomonas

(A, D and F) and Klebsiella pneumoniae strain 90 and 99 (Cook and Hutter 1981). Aminohydrolases,

which catalyze ring deamination, and amidohydrolases catalyze this conversion. These genes were

discovered through transposon mutagenesis (Eaton and Karns 1991). Recently pure culture of

Pseudomonas sp., ADP was identified which can mineralize the complete ring of atrazine to CO2

and hydroxyatrazine and polar metabolites.

8.3.10 Polycyclic Aromatic Hydrocarbons (PAHs)

PAHs (Polycyclic Aromatic Hydrocarbons) are both mutagenic and carcinogenic (Jones et al. 1989).

The combustion of organic matter, as well as the processing and use of fossil fuels, are the sources

of these pollutants. Pseudomonas sp., strain IOCa11 demonstrated broad substrate specificity for

PAHs including dibenzothiophene, benzo (α) pyrene, naphthalene and phenanthrene from oil­