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Bioremediation for Sustainable Environmental Cleanup

Table 7.2. The remediation of pesticides by common bacterial strains from the environment.

Bacterial strain

Pesticide

Remediation (%)

Retention time

References

Acinetobacter

Diazinon

88.27

20d

Amani et al. 2018

Pseudomonas

Chlorpyrifos

65

6d

Ajaz et al. 2012

Endosulfan

70–80

5d

Zaffar et al. 2018

DDT

67.55

7d

Powthong et al. 2016

Atrazine

99.9

2d

Cai et al. 2003

Bacillus

Fipronil

73

42d

Mandal et al. 2013

Mesotrione

99

5h

Sun et al. 2020

DDT

67.55

7d

Powthong et al. 2016

Imidacloprid

25.36–45.48

25d

Sabourmoghaddam et al. 2015

Klebsiella

Imidacloprid

78

7d

Phugare et al. 2013

Burkholderia

Dieldrin

39

7d

Matsumoto et al. 2008

Endrin

74

14d

Matsumoto et al. 2008

DDT – Dichlorodiphenyltrichloroethane; d – days; hr – hours

bioremediation of diverse chemical classes (Singh et al. 2020). Pesticides are remediated by bacteria

based on species specificity and several abiotic factors, such as temperature, pH, nutrient content,

moisture and humidity (Huang et al. 2018). Among pesticides, bacteria are the main degraders

of organochlorines. These are synthetic organic compounds containing at least one covalently

bonded chlorine atom and are insecticides primarily composed of carbon, hydrogen and chlorine.

Some of the most known organochlorine pesticides include, dieldrin, aldrin, lindane, endosulfan,

dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH). Pesticides containing

organophosphates (imidacloprid, diazinon and chlorpyrifos) are also among the chemical groups

investigated for degradation by bacteria (Jayaraj et al. 2016).

A few earlier reports (Table 7.2) had suggested the potential of Pseudomonas sp. for the

remediation of insecticides and herbicides. Endosulfan (insecticide) was bioremediated by

Pseudomonas fluorescens during a 5 d laboratory study. The results of the study showed that up to

80% of endosulfan could be remediated (Zaffar et al. 2018). In another study, approximately 99.9%

of atrazine (herbicide) was remediated after 2 d incubation with Pseudomonas sp. There has also been

research into the use of bacterial mixtures for pesticide remediation (Cai et al. 2003). When a mixture

of Pseudomonas stutzeri, Pseudomonas aeruginosa and Bacillus firmus was used in a week-long

laboratory study, approximately 68% of the DDT (insecticide) was remediated. Imidacloprid, another

insecticide, was remediated by Klebsiella pneumonia (78%) and Bacillus subtilis (25.36–45.48%)

during 7-d and 25-d experiments, respectively (Phugare et al. 2013, Sabourmoghaddam et al. 2015).

Additionally, Burkholderia and Acinetobacter were found to be capable of remediating pesticides

during tests conducted over a week. Almost all the potential bacterial strains were isolated from soil

samples, indicating the cost-effectiveness of using indigenous bacteria for pesticide remediation.

Bacteria can interact, both chemically and physically, with substances, leading to structural

changes or complete degradation of the target molecule (Ortiz-Hernández et al. 2013). Bacteria

can transform or degrade pesticides into less toxic or non-toxic forms (McGuinness and Dowling

2009). This is commonly known as a detoxification mechanism (Figure 7.2), where bacteria produce

intracellular and extracellular enzymes (Singh et al. 2020). The activity of enzymes depends on the

metabolic potential of the bacteria to detoxify or transform the pollutants, which depends on both

accessibility and bioavailability (Ramakrishnan et al. 2011). There could be three phases to the

metabolism of pesticides. Phase one involves the transformation of the initial properties of the parent

compound through oxidation, reduction or hydrolysis. This transformation produces a more water-

soluble and usually less toxic product than the parent. In the second phase, a pesticide or pesticide