enzymes that are somewhat more tolerant to high concentrations of contaminants
and lead to improved bioremediation (Fragoeiro 2005). Fungi can degrade a wide
variety of pesticides by introducing small structural changes in the molecule. Fungal
bioremediation of pesticides is caused by the release of a mixture of extracellular
enzymes such as laccases, polyphenol oxidases, and lignin peroxidases. Intracellular
enzymes such as reductases, methyltransferases, and cytochrome oxygenase were
also involved in the remediation of organic pollutants and reduced these pollutants to
a lesser or nontoxic form. The biotransformed pesticide was released into the soil,
where it was further degraded by bacteria (Gianfreda and Rao 2004; Slaoui et al.
2007; Bisht et al. 2015; Bisht and Harsh 2017).
Various fungi such as Penicillium (Peng et al. 2012), Aspergillus (Mohamed et al.
2011), and Phanerochaete spp. (Chirnside et al. 2011) showed an effective remediation of pesticides. Fusarium verticillioides showed the potential to use lindane as a
source of carbon and energy under aerobic conditions (Pinto et al. 2012). Other
fungal strains, viz. Fusarium oxysporum, Lentinula edodes, Penicillium
brevicompactum, and Lecanicillium saksenae, caused the biodegradation of the
pesticides terbuthylazine, pendimethalin, and difenoconazole (Hai et al. 2012).
Ellegaard-Jensen et al. (2014) mineralized the phenyl urea herbicide diuron using
a consortium of fungi and bacteria. Clothianidin was biotransformed by a white rot
fungus Phanerochaete sordida, which converted clothionidin into the non-toxic
metabolite N-(2-chlorothiazol-5-methyl)-N-methyl urea (TZMU) (Mori et al. 2017).
Endosulfan-decomposing aerobic fungal strains were found useful in soil contaminated with organochlorine pesticides. For example, Mortierella spp. strains W8
and Cm1–45 caused 50–70% degradation of endosulfan lactone (Kataoka et al.
2010). During endosulfan degradation, diol was initially formed, which was later
converted to endosulfan lactone. Mixed fungal species have more likely to degrade
mixed pesticides such as chlorpyrifos and DDT. Decomposition efficiency was
found to be higher using low mixed insecticide concentrations (Kulshrestha and
Kumari 2010). The efficacy was observed in degradation of DDT and chlorpyrifos at
26.94% and 24.94%, respectively. Under severe conditions, the genus
Sphingomonas yanoikuyae can decompose carbamate and pyrethrin (OPs) in enrichment culture with high efficiency (Ouyang et al. 2008). Gliocladium showed maximum potential for degradation of carbofuran (Seo et al. 2005). Trichoderma
harzianum and T. viride showed a high efficiency in the degradation of pyrimicarb
and increased degradation potential when activated charcoal was added (Romeh
2001).
2.5 Factors Affecting Microbial Degradation of Pesticides
The use of pesticides is essential for agricultural production, and hence, many
problems of environmental pollution and health hazards have become increasingly
prominent. Various microorganisms play an important role in the bioremediation of
pesticides. However, the microbial degradation of pesticide residues is limited by a
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
41
and lead to improved bioremediation (Fragoeiro 2005). Fungi can degrade a wide
variety of pesticides by introducing small structural changes in the molecule. Fungal
bioremediation of pesticides is caused by the release of a mixture of extracellular
enzymes such as laccases, polyphenol oxidases, and lignin peroxidases. Intracellular
enzymes such as reductases, methyltransferases, and cytochrome oxygenase were
also involved in the remediation of organic pollutants and reduced these pollutants to
a lesser or nontoxic form. The biotransformed pesticide was released into the soil,
where it was further degraded by bacteria (Gianfreda and Rao 2004; Slaoui et al.
2007; Bisht et al. 2015; Bisht and Harsh 2017).
Various fungi such as Penicillium (Peng et al. 2012), Aspergillus (Mohamed et al.
2011), and Phanerochaete spp. (Chirnside et al. 2011) showed an effective remediation of pesticides. Fusarium verticillioides showed the potential to use lindane as a
source of carbon and energy under aerobic conditions (Pinto et al. 2012). Other
fungal strains, viz. Fusarium oxysporum, Lentinula edodes, Penicillium
brevicompactum, and Lecanicillium saksenae, caused the biodegradation of the
pesticides terbuthylazine, pendimethalin, and difenoconazole (Hai et al. 2012).
Ellegaard-Jensen et al. (2014) mineralized the phenyl urea herbicide diuron using
a consortium of fungi and bacteria. Clothianidin was biotransformed by a white rot
fungus Phanerochaete sordida, which converted clothionidin into the non-toxic
metabolite N-(2-chlorothiazol-5-methyl)-N-methyl urea (TZMU) (Mori et al. 2017).
Endosulfan-decomposing aerobic fungal strains were found useful in soil contaminated with organochlorine pesticides. For example, Mortierella spp. strains W8
and Cm1–45 caused 50–70% degradation of endosulfan lactone (Kataoka et al.
2010). During endosulfan degradation, diol was initially formed, which was later
converted to endosulfan lactone. Mixed fungal species have more likely to degrade
mixed pesticides such as chlorpyrifos and DDT. Decomposition efficiency was
found to be higher using low mixed insecticide concentrations (Kulshrestha and
Kumari 2010). The efficacy was observed in degradation of DDT and chlorpyrifos at
26.94% and 24.94%, respectively. Under severe conditions, the genus
Sphingomonas yanoikuyae can decompose carbamate and pyrethrin (OPs) in enrichment culture with high efficiency (Ouyang et al. 2008). Gliocladium showed maximum potential for degradation of carbofuran (Seo et al. 2005). Trichoderma
harzianum and T. viride showed a high efficiency in the degradation of pyrimicarb
and increased degradation potential when activated charcoal was added (Romeh
2001).
2.5 Factors Affecting Microbial Degradation of Pesticides
The use of pesticides is essential for agricultural production, and hence, many
problems of environmental pollution and health hazards have become increasingly
prominent. Various microorganisms play an important role in the bioremediation of
pesticides. However, the microbial degradation of pesticide residues is limited by a
2 Bioremediation of Pesticides: An Eco-Friendly Approach for Environment. . .
41