(Natesan and Shanmugasundaram 1989). Cyanobacteria could replace the nitrogen
and phosphate fertilizer efficiently.
5.4 Heavy Metal Contamination in Soil
Heavy metals are naturally present in biosphere, hydrosphere, lithosphere and
lithosphere. Due to urbanization and industrialization, heavy metals have been
included in almost all materials that are used in day-to-day life and result in
anthropogenic activity. Improper disposal of heavy metals leads to soil and water
contamination while irrigation of such contaminated water further affects the agricultural ecosystem. Apart from irrigation, pesticides and herbicides also serve as a
source of heavy metal contamination (Li et al. 2019a). Consumption of heavy metal–
contaminated food results in neurotoxicity, carcinogenesis, cell damage and loss of
cellular functions in humans (Engwa et al. 2019). Microbial bioremediation has
different processes which include bioaccumulation, bioleaching, biosorption, biotransformation and biomineralization, and the principle behind this process includes
binding, immobilization, oxidation, transformation and volatizing of heavy metals
(Verma and Kuila 2019).
Cyanobacteria has a major role in bioremediation of heavy metals. Photosynthetic
organism generally requires metals which act as cofactors for several metabolism
and in turn maintains metal homeostasis. Role of copper, nickel, cobalt, zinc, iron,
manganese and magnesium in cyanobacterial metabolism was clearly studied;
hence, the cyanobacteria undergo accumulation and transformation of heavy metals
for their metabolism, thereby reduce the heavy metal contaminants in soils (Huertas
et al. 2014). Biosorbent capability of Fe, Ni, Cr, Cd and Zn by Nostoc sp. was
reported. Similarly, adsorption of Cr and Cu by Spirulina sp. and Spirogyra sp. was
also studied (Igiri et al. 2018).
Waste effluents from industries include large amount of heavy metals. EPS
producing microorganisms are used to remove heavy metal contents as the EPS
are negatively charged molecules which act as biosorption of heavy metals. Further
on extraction of EPS from effluents removes the heavy metals, thus the effluents are
heavy metal free. Unique feature of cyanobacterial EPS is complex polysaccharide
with more than six monomer types, which results in versatile EPS production. Hence
the cyanobacterial EPS can used to remove or accumulate heavy metals in contaminated soil and water (Bhunia et al. 2018). Nostoc muscorum isolated from polluted
water was reported with the potential to remove Zn
2+ , and it is evidenced that the
negative charge of hydroxyl, carbonyl, alcohol, amine, phosphoryl, sulfhydryl and
carboxyl on surface of EPS is produced by Nostoc muscorum (Diengdoh et al. 2017).
Consortium of algae with Spirulina platensis showed effective bioremediation in
waste water and agricultural drainage water containing organophosphorus pesticide
malathion and heavy metals, viz. nickel, lead and cadmium (Abdel-Razek et al.
2019).
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K. G. Sabarinathan et al.
and phosphate fertilizer efficiently.
5.4 Heavy Metal Contamination in Soil
Heavy metals are naturally present in biosphere, hydrosphere, lithosphere and
lithosphere. Due to urbanization and industrialization, heavy metals have been
included in almost all materials that are used in day-to-day life and result in
anthropogenic activity. Improper disposal of heavy metals leads to soil and water
contamination while irrigation of such contaminated water further affects the agricultural ecosystem. Apart from irrigation, pesticides and herbicides also serve as a
source of heavy metal contamination (Li et al. 2019a). Consumption of heavy metal–
contaminated food results in neurotoxicity, carcinogenesis, cell damage and loss of
cellular functions in humans (Engwa et al. 2019). Microbial bioremediation has
different processes which include bioaccumulation, bioleaching, biosorption, biotransformation and biomineralization, and the principle behind this process includes
binding, immobilization, oxidation, transformation and volatizing of heavy metals
(Verma and Kuila 2019).
Cyanobacteria has a major role in bioremediation of heavy metals. Photosynthetic
organism generally requires metals which act as cofactors for several metabolism
and in turn maintains metal homeostasis. Role of copper, nickel, cobalt, zinc, iron,
manganese and magnesium in cyanobacterial metabolism was clearly studied;
hence, the cyanobacteria undergo accumulation and transformation of heavy metals
for their metabolism, thereby reduce the heavy metal contaminants in soils (Huertas
et al. 2014). Biosorbent capability of Fe, Ni, Cr, Cd and Zn by Nostoc sp. was
reported. Similarly, adsorption of Cr and Cu by Spirulina sp. and Spirogyra sp. was
also studied (Igiri et al. 2018).
Waste effluents from industries include large amount of heavy metals. EPS
producing microorganisms are used to remove heavy metal contents as the EPS
are negatively charged molecules which act as biosorption of heavy metals. Further
on extraction of EPS from effluents removes the heavy metals, thus the effluents are
heavy metal free. Unique feature of cyanobacterial EPS is complex polysaccharide
with more than six monomer types, which results in versatile EPS production. Hence
the cyanobacterial EPS can used to remove or accumulate heavy metals in contaminated soil and water (Bhunia et al. 2018). Nostoc muscorum isolated from polluted
water was reported with the potential to remove Zn
2+ , and it is evidenced that the
negative charge of hydroxyl, carbonyl, alcohol, amine, phosphoryl, sulfhydryl and
carboxyl on surface of EPS is produced by Nostoc muscorum (Diengdoh et al. 2017).
Consortium of algae with Spirulina platensis showed effective bioremediation in
waste water and agricultural drainage water containing organophosphorus pesticide
malathion and heavy metals, viz. nickel, lead and cadmium (Abdel-Razek et al.
2019).
146
K. G. Sabarinathan et al.