8.4 Biological Elements for Green Synthesis
8.4.1 Bacteria
In the recent studies, it was investigated that research has very much focused on
prokaryotic microorganisms for the purpose of metallic nanoparticle production.
Because of their large numbers as well as their capability to settle in extreme
environmental situation, bacteria are considered as a favorable candidate for investigation. Further, they have a rapid growing capability and are simple to manipulate
and economical to cultivate (Iravani et al. 2014). Bacteria are identified for intra- as
well as extracellular formation of organic with inorganic compounds. In order to
illustrate this, inorganic materials like magnetic nanoparticles are synthesized by
magnetotactic bacteria (Grasso et al. 2019). Likewise, calcium carbonate and nanogypsum layers are synthesized with S-layer bacteria (Madakka et al. 2018). In
response to the toxicity of metals, a few bacteria evolve a resistance that helps to
diminish them into metal nanoparticles (Niño-Martínez et al. 2019; Gahlawat and
Choudhury 2019). On the contrary, a variety of metal ions, usually within the
d-block transition metals (V, Ti, Cr, Co, Ni, Cu, Zn, Tb, W, Ag, Cd, Au, Hg), and
a couple of other metals and metalloids in groups 13–16 belonging to the periodic
table (Al, Ga, Ge, As, Se, Sn, Sb, Te, Pb, and Bi) are lethal to bacteria and examined
for their antimicrobial properties.
Among the noble metallic nanoparticles, silver nanoparticles (AgNPs) are the
predominant choice for responding to a range of medical issues owing to their
chemical biocompatibility, inertness, oxidation, resistance, and wide spectrum of
antimicrobial activity amidst a varied range of bacteria and fungi (Lee and Jun 2019).
Also, silver is well recognized for its biocidal characteristics, and it has an efficient
antimicrobial activity in the presence of Gram-positive and Gram-negative bacteria,
together with extremely resistant strain Staphylococcus aureus (Vila Domínguez
et al. 2020).
Correspondingly, various copper and copper alloys have established similar
function against other pathogenic bacteria particularly epidemic methicillin-resistant
Staphylococcus aureus (EMRSA), Escherichia coli O157:H7, Listeria
monocytogenes, and vancomycin-resistant Enterococci (Warnes and Keevil 2011).
In recent times, researchers have made several trials to make use of microorganisms as a promising and eco-friendly means for the production of metallic
nanoparticles. A variety of microbes have the ability to reduce the silver ions
(Ag
+ ) to produce silver nanoparticles (Dakal et al. 2016; Hamouda et al.
2019a, b). The first known evidence of a bacterium employed to synthesize silver
nanoparticles (AgNPs) was recorded using the Pseudomonas stutzeri AG259 strain
isolated from a silver mine (Rajora et al. 2016; Gahlawat and Choudhury 2019).
Recently, Saravanan et al., in 2017, exemplified the synthesis of AgNPs by utilizing
bacterial exopolysaccharide (EPS) both as a reducing and as a stabilizing agent.
These EPS-stabilized AgNPs have utility in an eco-friendly and a cheaper strategy
for the degradation of harmful azo dyes with potential applications in textile
190
T. Singh et al.
8.4.1 Bacteria
In the recent studies, it was investigated that research has very much focused on
prokaryotic microorganisms for the purpose of metallic nanoparticle production.
Because of their large numbers as well as their capability to settle in extreme
environmental situation, bacteria are considered as a favorable candidate for investigation. Further, they have a rapid growing capability and are simple to manipulate
and economical to cultivate (Iravani et al. 2014). Bacteria are identified for intra- as
well as extracellular formation of organic with inorganic compounds. In order to
illustrate this, inorganic materials like magnetic nanoparticles are synthesized by
magnetotactic bacteria (Grasso et al. 2019). Likewise, calcium carbonate and nanogypsum layers are synthesized with S-layer bacteria (Madakka et al. 2018). In
response to the toxicity of metals, a few bacteria evolve a resistance that helps to
diminish them into metal nanoparticles (Niño-Martínez et al. 2019; Gahlawat and
Choudhury 2019). On the contrary, a variety of metal ions, usually within the
d-block transition metals (V, Ti, Cr, Co, Ni, Cu, Zn, Tb, W, Ag, Cd, Au, Hg), and
a couple of other metals and metalloids in groups 13–16 belonging to the periodic
table (Al, Ga, Ge, As, Se, Sn, Sb, Te, Pb, and Bi) are lethal to bacteria and examined
for their antimicrobial properties.
Among the noble metallic nanoparticles, silver nanoparticles (AgNPs) are the
predominant choice for responding to a range of medical issues owing to their
chemical biocompatibility, inertness, oxidation, resistance, and wide spectrum of
antimicrobial activity amidst a varied range of bacteria and fungi (Lee and Jun 2019).
Also, silver is well recognized for its biocidal characteristics, and it has an efficient
antimicrobial activity in the presence of Gram-positive and Gram-negative bacteria,
together with extremely resistant strain Staphylococcus aureus (Vila Domínguez
et al. 2020).
Correspondingly, various copper and copper alloys have established similar
function against other pathogenic bacteria particularly epidemic methicillin-resistant
Staphylococcus aureus (EMRSA), Escherichia coli O157:H7, Listeria
monocytogenes, and vancomycin-resistant Enterococci (Warnes and Keevil 2011).
In recent times, researchers have made several trials to make use of microorganisms as a promising and eco-friendly means for the production of metallic
nanoparticles. A variety of microbes have the ability to reduce the silver ions
(Ag
+ ) to produce silver nanoparticles (Dakal et al. 2016; Hamouda et al.
2019a, b). The first known evidence of a bacterium employed to synthesize silver
nanoparticles (AgNPs) was recorded using the Pseudomonas stutzeri AG259 strain
isolated from a silver mine (Rajora et al. 2016; Gahlawat and Choudhury 2019).
Recently, Saravanan et al., in 2017, exemplified the synthesis of AgNPs by utilizing
bacterial exopolysaccharide (EPS) both as a reducing and as a stabilizing agent.
These EPS-stabilized AgNPs have utility in an eco-friendly and a cheaper strategy
for the degradation of harmful azo dyes with potential applications in textile
190
T. Singh et al.