The vermicompost is rich in nutrients, odor free, more mature, and stabilized than
the initial waste mixture. Though P. hysterophorus enhanced the average body
weight of earthworms, it reduced the growth rate of earthworms, cocoon formation,
and number of hatchings during vermicomposting. Thus, it affected the growth and
reproduction efficacy of earthworm. If P. hysterophorus was used in higher concentrations, it may inhibit the vermicomposting efficiency of earthworms.
15.2.4 Biochemical Parameters
Biological markers are regarded as fast, diagnostic, and prognostic early warning of
toxicity. These markers are used to detect and assess the impact of wide range of
contaminants present in the environment (Lourenço et al. 2011a). Living organisms
exposed to contaminated environments showed significant deleterious effects (Ajani
2014). Stress caused by environmental conditions activates the endogenous production of reactive oxygen species (ROS), such as superoxide radicals (O
2À
), hydrogen
peroxide (H 2 O 2 ), and hydroxyl radical (OH
À ), most of which are side products of
tissue respiration (Valavanidis et al. 2009). Due to their unstable nature, ROS affects
biomolecules by interacting aggressively with polysaturated fatty acids, proteins,
and DNA (Damien et al. 2004), and this further results in oxidative stress. Oxidative
stress is an imbalance between the antioxidant defense systems and production of
free radicals. The potential of oxidative damage is mainly affected by the level of
target molecules, that is, polysaturated fatty acids (PUFA), which are easily oxidized
by reactive oxygen species to lipid peroxides (Di Giulio et al. 1995). The antioxidant
system constitutes various enzymes, such as superoxide dismutase (SOD), catalase
(CAT), and glutathione peroxidase (GPx), which counteract this oxidative stress.
Malondialdehyde (MDA) is the oxidized product of lipid membrane, and it could
be used as a sensitive biomarker of injury in cells (Xue et al. 2009). It is an important
indicator of ROS peroxidation (Stohs and Bagchi 1995). The degree of lipid
peroxidation may depend on the composition of fatty acids and levels of antioxidant
enzymes in the organism (Kiran and Aruna 2010). The MDA level increases with the
effect of toxicity. The elevated lipid peroxide level suggests hydroxyl radical activity
and indicates oxidative damage (Kenneth 2000); as a result, it enhances the MDA
level that is due to the formation of ROS. Luo et al. (2005) asserted that the
peroxidation of membrane lipids is one of the major damaging effects of reactive
oxygen species and their products in cells, which can be indicated by MDA
detection.
Superoxide dismutase (SOD) is the first line of defense that catalyzes dismutation
of superoxide anion into O 2 and H 2 O 2 . SOD shows increment due to the treatment
with toxicity, which indicates that the SOD is biosynthesized to react with O
2À to
avoid the oxidant damage of cells (Singh et al. 2006). The enhanced activity of SOD
resulted in increased H 2 O 2 . Thus, the increment is due to increased activity of
enzymes to remove H 2 O 2 to reduce oxidative damage in the exposed earthworms
(Zhang et al. 2015). Some toxic substances decrease the SOD activity. It may be due
256
H. Kaur et al.
the initial waste mixture. Though P. hysterophorus enhanced the average body
weight of earthworms, it reduced the growth rate of earthworms, cocoon formation,
and number of hatchings during vermicomposting. Thus, it affected the growth and
reproduction efficacy of earthworm. If P. hysterophorus was used in higher concentrations, it may inhibit the vermicomposting efficiency of earthworms.
15.2.4 Biochemical Parameters
Biological markers are regarded as fast, diagnostic, and prognostic early warning of
toxicity. These markers are used to detect and assess the impact of wide range of
contaminants present in the environment (Lourenço et al. 2011a). Living organisms
exposed to contaminated environments showed significant deleterious effects (Ajani
2014). Stress caused by environmental conditions activates the endogenous production of reactive oxygen species (ROS), such as superoxide radicals (O
2À
), hydrogen
peroxide (H 2 O 2 ), and hydroxyl radical (OH
À ), most of which are side products of
tissue respiration (Valavanidis et al. 2009). Due to their unstable nature, ROS affects
biomolecules by interacting aggressively with polysaturated fatty acids, proteins,
and DNA (Damien et al. 2004), and this further results in oxidative stress. Oxidative
stress is an imbalance between the antioxidant defense systems and production of
free radicals. The potential of oxidative damage is mainly affected by the level of
target molecules, that is, polysaturated fatty acids (PUFA), which are easily oxidized
by reactive oxygen species to lipid peroxides (Di Giulio et al. 1995). The antioxidant
system constitutes various enzymes, such as superoxide dismutase (SOD), catalase
(CAT), and glutathione peroxidase (GPx), which counteract this oxidative stress.
Malondialdehyde (MDA) is the oxidized product of lipid membrane, and it could
be used as a sensitive biomarker of injury in cells (Xue et al. 2009). It is an important
indicator of ROS peroxidation (Stohs and Bagchi 1995). The degree of lipid
peroxidation may depend on the composition of fatty acids and levels of antioxidant
enzymes in the organism (Kiran and Aruna 2010). The MDA level increases with the
effect of toxicity. The elevated lipid peroxide level suggests hydroxyl radical activity
and indicates oxidative damage (Kenneth 2000); as a result, it enhances the MDA
level that is due to the formation of ROS. Luo et al. (2005) asserted that the
peroxidation of membrane lipids is one of the major damaging effects of reactive
oxygen species and their products in cells, which can be indicated by MDA
detection.
Superoxide dismutase (SOD) is the first line of defense that catalyzes dismutation
of superoxide anion into O 2 and H 2 O 2 . SOD shows increment due to the treatment
with toxicity, which indicates that the SOD is biosynthesized to react with O
2À to
avoid the oxidant damage of cells (Singh et al. 2006). The enhanced activity of SOD
resulted in increased H 2 O 2 . Thus, the increment is due to increased activity of
enzymes to remove H 2 O 2 to reduce oxidative damage in the exposed earthworms
(Zhang et al. 2015). Some toxic substances decrease the SOD activity. It may be due
256
H. Kaur et al.