number of intrinsic and extrinsic environmental factors. The effect of intrinsic
factors has derived from the structure of the pesticide and the microorganisms.
The physical and chemical parameters of the soil, i.e., organic matter, nutrients,
temperature, pH, humidity, redox conditions, amount, and nature of clay were found
to have a direct impact on the success of bioremediation. Schroll et al. (2006)
investigated the potential of soil moisture in the aerobic microbial mineralization
of certain pesticides, i.e., glyphosate and benzoin ethyl in different soils. They
observed a linear relationship between increasing soil moisture and pesticide
degradation.
2.5.1 Effect of Microbial Species, Metabolic Activity,
and Adaptability
Different species of microorganisms perform different reactions to the same organic
substrate and pesticide degradation products were found to be different, and the
microorganisms showed strong potential for adaptation in pesticide-contaminated
soils (Hugo et al. 2014). Through the adapted process, new intermediate compounds
were discovered to stimulate microorganisms to produce the corresponding enzyme
system or to establish a new enzyme system to degrade the pesticide. Changes in the
functional properties and degradation of the pesticide were the most important
factors (Hussain et al. 2009; Tsai et al. 2011; Zhang et al. 2015).
2.5.2 Effect of Pesticide Structure
The molecular weight, spatial structure, number and type of substituents, substituted
properties, and location were identified to affect the rate and efficiency of microbial
degradation of pesticides (Mahro et al. 2012; Chaw and Stoklas 2013). In general,
the polymer and composite pesticides were more resistant to biodegradation, and the
simpler structure was more easily degradable (Luan et al. 2006). The main route of
phytoremediation on soil contaminated by polycyclic aromatic hydrocarbons
(PAHs) was microbial degradation in the rhizosphere. The number of benzene
rings of PAHs had a great effect on the microbial degradation of PAHs. Two-rings
and tricyclic compounds such as naphthalene, phenanthrene, anthracene, and
fluorene existed in the atmosphere for a short time and microorganisms easily
mineralized these compounds with using PAHs as a sole carbon source. However,
high-molecular-weight four-ring and other multi-ring PAHs were stable in the
atmosphere. However, white rot fungi could degrade these compounds through
metabolism (Acevedo et al. 2011). In general, as the number of benzene rings of
PAHs increased, the octanol/water partition coefficient increased, and the rate of
degradation was decreased.
42
A. Sehrawat et al.
factors has derived from the structure of the pesticide and the microorganisms.
The physical and chemical parameters of the soil, i.e., organic matter, nutrients,
temperature, pH, humidity, redox conditions, amount, and nature of clay were found
to have a direct impact on the success of bioremediation. Schroll et al. (2006)
investigated the potential of soil moisture in the aerobic microbial mineralization
of certain pesticides, i.e., glyphosate and benzoin ethyl in different soils. They
observed a linear relationship between increasing soil moisture and pesticide
degradation.
2.5.1 Effect of Microbial Species, Metabolic Activity,
and Adaptability
Different species of microorganisms perform different reactions to the same organic
substrate and pesticide degradation products were found to be different, and the
microorganisms showed strong potential for adaptation in pesticide-contaminated
soils (Hugo et al. 2014). Through the adapted process, new intermediate compounds
were discovered to stimulate microorganisms to produce the corresponding enzyme
system or to establish a new enzyme system to degrade the pesticide. Changes in the
functional properties and degradation of the pesticide were the most important
factors (Hussain et al. 2009; Tsai et al. 2011; Zhang et al. 2015).
2.5.2 Effect of Pesticide Structure
The molecular weight, spatial structure, number and type of substituents, substituted
properties, and location were identified to affect the rate and efficiency of microbial
degradation of pesticides (Mahro et al. 2012; Chaw and Stoklas 2013). In general,
the polymer and composite pesticides were more resistant to biodegradation, and the
simpler structure was more easily degradable (Luan et al. 2006). The main route of
phytoremediation on soil contaminated by polycyclic aromatic hydrocarbons
(PAHs) was microbial degradation in the rhizosphere. The number of benzene
rings of PAHs had a great effect on the microbial degradation of PAHs. Two-rings
and tricyclic compounds such as naphthalene, phenanthrene, anthracene, and
fluorene existed in the atmosphere for a short time and microorganisms easily
mineralized these compounds with using PAHs as a sole carbon source. However,
high-molecular-weight four-ring and other multi-ring PAHs were stable in the
atmosphere. However, white rot fungi could degrade these compounds through
metabolism (Acevedo et al. 2011). In general, as the number of benzene rings of
PAHs increased, the octanol/water partition coefficient increased, and the rate of
degradation was decreased.
42
A. Sehrawat et al.