1983). The main advantage of biosorption over conventional treatment approach is
its cost-effectiveness, great efficiency, reduction of chemical as well as biological
sludge, sensitivity towards particular metals, no extra nutrient necessity, renewal of
the biosorbent and the possibility of metal recovery (Fan et al. 2007; Garbisu and
Alkorta 2001). Various prokaryotes as well as eukaryotes remove harmful heavy
metal ions, because of different natural abilities to biosorb, which provides them
differing tolerance at 10–20 mg/L of metal ions because of their mobility, solubility
and bioavailability potential (Gadd and White 1993; Gawali et al. 2014; Gomes et al.
2013; Goyal et al. 2003). A new technique biosorption has been explored for the
elimination of toxic metals from contaminated sites which is dependent on the metal
binding capability of various biological materials.
There is a need to isolate bacterial strains with new metabolic capabilities to start
both biochemical and genetical degradation pathways. Bacillus (Hamer 1986;
Hameed 2006), Pseudomonas (Huckle et al. 1993; Huston et al. 2002) and Streptomyces (Infante et al. 2014; Jain et al. 2012) are powerful metal sorbent bacteria.
Biosorption in mixtures that change qualitatively and quantitatively is based on two
methods – active and passive, which are metabolism-independent and metabolismdependent (Jain and Bhatt 2014), respectively – and depends on biomass variety, its
origin, possibility and processing type. In addition to biosorption, certain other
advantageous processes like ion exchange, complexation, precipitation, adsorption,
siderophores, biosurfactants, oxidation-reduction (redox), biomethylation, metalbinding cysteine-rich peptides, metallothioneins (MTs), glutathione (GSH), natural
phytochelatins (PCs) and synthetic phytochelatin (EC20) as well as the “cell-surface
display” system remediate heavy metals. There is a requirement to improve these
techniques for the remediating heavy metals for the welfare of mankind (Gupta et al.
2016; Thakare et al. 2021)
12.3 Microbial Diversity and Bioremediation
Bioremediation employ microbes to eliminate, counteract, or detoxify contaminants
from the polluted environment. There are various studies concerning the characterization of the bacterial population, their reaction to contaminants, recognition of
genes required for degradation, and a lot of others (Das 2014). According to various
reports, the presence of a large number of unidentified microbes assisting in bioremediation of polluted environment can be detected only through the strategies which
do not depend upon culture (Marzorati et al. 2010). Gene analysis of 16S rRNA has
changed the way of detecting the microbial variety in the natural environment
through both culture-dependent and culture-independent strategies (Das et al.
2014). No standard method is available for evaluating environmental microflora
for application in bioremediation practices, although polyphasic strategies are
employed widely for studying microbial variety in the environment. Molecular
biology techniques are widely used in studying microbial ecology. In fact, a clear
understanding of the function of metal-resistant genes from the different microbial
population is required before their use in polluted environments (Dash and Das
12 Remediation of Heavy Metals Through Genetically Engineered Microorganism
319
its cost-effectiveness, great efficiency, reduction of chemical as well as biological
sludge, sensitivity towards particular metals, no extra nutrient necessity, renewal of
the biosorbent and the possibility of metal recovery (Fan et al. 2007; Garbisu and
Alkorta 2001). Various prokaryotes as well as eukaryotes remove harmful heavy
metal ions, because of different natural abilities to biosorb, which provides them
differing tolerance at 10–20 mg/L of metal ions because of their mobility, solubility
and bioavailability potential (Gadd and White 1993; Gawali et al. 2014; Gomes et al.
2013; Goyal et al. 2003). A new technique biosorption has been explored for the
elimination of toxic metals from contaminated sites which is dependent on the metal
binding capability of various biological materials.
There is a need to isolate bacterial strains with new metabolic capabilities to start
both biochemical and genetical degradation pathways. Bacillus (Hamer 1986;
Hameed 2006), Pseudomonas (Huckle et al. 1993; Huston et al. 2002) and Streptomyces (Infante et al. 2014; Jain et al. 2012) are powerful metal sorbent bacteria.
Biosorption in mixtures that change qualitatively and quantitatively is based on two
methods – active and passive, which are metabolism-independent and metabolismdependent (Jain and Bhatt 2014), respectively – and depends on biomass variety, its
origin, possibility and processing type. In addition to biosorption, certain other
advantageous processes like ion exchange, complexation, precipitation, adsorption,
siderophores, biosurfactants, oxidation-reduction (redox), biomethylation, metalbinding cysteine-rich peptides, metallothioneins (MTs), glutathione (GSH), natural
phytochelatins (PCs) and synthetic phytochelatin (EC20) as well as the “cell-surface
display” system remediate heavy metals. There is a requirement to improve these
techniques for the remediating heavy metals for the welfare of mankind (Gupta et al.
2016; Thakare et al. 2021)
12.3 Microbial Diversity and Bioremediation
Bioremediation employ microbes to eliminate, counteract, or detoxify contaminants
from the polluted environment. There are various studies concerning the characterization of the bacterial population, their reaction to contaminants, recognition of
genes required for degradation, and a lot of others (Das 2014). According to various
reports, the presence of a large number of unidentified microbes assisting in bioremediation of polluted environment can be detected only through the strategies which
do not depend upon culture (Marzorati et al. 2010). Gene analysis of 16S rRNA has
changed the way of detecting the microbial variety in the natural environment
through both culture-dependent and culture-independent strategies (Das et al.
2014). No standard method is available for evaluating environmental microflora
for application in bioremediation practices, although polyphasic strategies are
employed widely for studying microbial variety in the environment. Molecular
biology techniques are widely used in studying microbial ecology. In fact, a clear
understanding of the function of metal-resistant genes from the different microbial
population is required before their use in polluted environments (Dash and Das
12 Remediation of Heavy Metals Through Genetically Engineered Microorganism
319