2.4.2 Algae and Cyanobacterial Degradation
Thengodkar and Sivakami (2010) reported that hydrolysis of the chlorpyrifos pesticide by the secretion of the enzyme alkaline phosphatase by Spirulina platensis led
to production of its non-toxic primary metabolite 3,5,6-trichloro-2-pyridinol. Kabra
et al. (2014) studied degradation of atrazine by the microalgal species
Chlamydomonas mexicana. The carbohydrate content in algae increases, which
proved that C. mexicana can evacuate the pesticides at polluted streams. Pesticide
remediation rate was found to vary depending on algal strain used, nature of
pollutants, and environmental factors such as nutrients, water, pH, salinity, oxygen
tension, temperature, and light intensity. Furthermore, physical and chemical parameters such as molecular chemistry, weight concentration, and toxicity have been
shown to have an effect on atrazine degradation (Priyadarshani et al. 2011; Varsha
et al. 2011).
Megharaj et al. (1987) reported the degradation of monocrotophos and
quinalphos (organophosphorus insecticides) over a period of 30 days by Chlorella
vulgaris, Scenedesmus bijugatus, Synechococcus elongatus, Phormidium tenue, and
Nostoc linckia. Anabaena spp. and Aulosira fertilissima were found to metabolize
DDT to DDD and DDE, respectively, by the process of bioaccumulation and
transformation (Lal and Lal 1987). Microalgae degraded the organophosphorus
insecticide methyl parathion and used it as a source of phosphate through a reductive
process (Barton et al. 2004). Chlamydomonas reinhardtii has been shown to be
useful in the bioremediation of prometryne (herbicide)-contaminated aquatic systems because it can rapidly uptake and catabolize prometryne (Jin et al. 2012).
C. vulgaris accumulated the triazine group of herbicides, while I. galbana and
Dunaliella tertiolecta accumulated atrazine (Weiner et al. 2004).
The endocrine disrupting insecticide, α-endosulfan was converted to endosulfan
sulfate, endosulfadiol, β-endosulfan, endosulfan aldehyde, and endosulfan ether by
Scenedesmus spp. and Chlorococcum spp. at cell densities of 1550 Â 10
6 and
600 Â 10
6 mg L
À1 in a defined liquid medium (Sethunathan et al. 2004). Zhang
et al. (2012) reported that Anabaena azotica strain 118 isolated from Chinese rice
soils degraded lindane at a concentration of 0.2 mg L
À1 . However, exposure to
microalgae to multiple toxic compounds could lead to the development of resistant
species, which may contribute to the degradation of more pesticide contaminants.
Therefore, microalgae species are highly recommended for the ecosystems contaminated with lindane pesticide.
2.4.3 Degradation by Fungi
The filamentous nature of fungal growth provides a major advantage over bacteria,
as it helps fungi to effectively propagate in the soil environment. In addition, during
hyphae colonization in the soil, the fungi produce substrate-specific extracellular
40
A. Sehrawat et al.
Thengodkar and Sivakami (2010) reported that hydrolysis of the chlorpyrifos pesticide by the secretion of the enzyme alkaline phosphatase by Spirulina platensis led
to production of its non-toxic primary metabolite 3,5,6-trichloro-2-pyridinol. Kabra
et al. (2014) studied degradation of atrazine by the microalgal species
Chlamydomonas mexicana. The carbohydrate content in algae increases, which
proved that C. mexicana can evacuate the pesticides at polluted streams. Pesticide
remediation rate was found to vary depending on algal strain used, nature of
pollutants, and environmental factors such as nutrients, water, pH, salinity, oxygen
tension, temperature, and light intensity. Furthermore, physical and chemical parameters such as molecular chemistry, weight concentration, and toxicity have been
shown to have an effect on atrazine degradation (Priyadarshani et al. 2011; Varsha
et al. 2011).
Megharaj et al. (1987) reported the degradation of monocrotophos and
quinalphos (organophosphorus insecticides) over a period of 30 days by Chlorella
vulgaris, Scenedesmus bijugatus, Synechococcus elongatus, Phormidium tenue, and
Nostoc linckia. Anabaena spp. and Aulosira fertilissima were found to metabolize
DDT to DDD and DDE, respectively, by the process of bioaccumulation and
transformation (Lal and Lal 1987). Microalgae degraded the organophosphorus
insecticide methyl parathion and used it as a source of phosphate through a reductive
process (Barton et al. 2004). Chlamydomonas reinhardtii has been shown to be
useful in the bioremediation of prometryne (herbicide)-contaminated aquatic systems because it can rapidly uptake and catabolize prometryne (Jin et al. 2012).
C. vulgaris accumulated the triazine group of herbicides, while I. galbana and
Dunaliella tertiolecta accumulated atrazine (Weiner et al. 2004).
The endocrine disrupting insecticide, α-endosulfan was converted to endosulfan
sulfate, endosulfadiol, β-endosulfan, endosulfan aldehyde, and endosulfan ether by
Scenedesmus spp. and Chlorococcum spp. at cell densities of 1550 Â 10
6 and
600 Â 10
6 mg L
À1 in a defined liquid medium (Sethunathan et al. 2004). Zhang
et al. (2012) reported that Anabaena azotica strain 118 isolated from Chinese rice
soils degraded lindane at a concentration of 0.2 mg L
À1 . However, exposure to
microalgae to multiple toxic compounds could lead to the development of resistant
species, which may contribute to the degradation of more pesticide contaminants.
Therefore, microalgae species are highly recommended for the ecosystems contaminated with lindane pesticide.
2.4.3 Degradation by Fungi
The filamentous nature of fungal growth provides a major advantage over bacteria,
as it helps fungi to effectively propagate in the soil environment. In addition, during
hyphae colonization in the soil, the fungi produce substrate-specific extracellular
40
A. Sehrawat et al.