344
N. B. Raj et al.
has thermodynamically controlled chemical compositions than top-down method
(Thakkar et al. 2010).
Physical and chemical methods result in controlled synthesis of NPs and can
yield large amount of NPs in shorter duration (Alkilany et al. 2015; He et al. 2015).
Regardless of the pervasive use of physical and chemical methods for NP synthesis,
growing body of evidences suggests that, there have been emerging issues such as
hazardous procedures, non-biodegradable, cumbersome, capital intensive, energy
intensive, toxic by-products, eutrophication, high monodispersity and requirement
for toxic chemicals, solvents, reducing agents, stabilizers, high temperature, metal
ions, reducing agents, pH and pressure for NP synthesis (Mallick et al. 2004). Hence,
the researchers round the globe are in quest for the ancillary route for efficient and
nature-friendly NP synthesis owing to their advantages as stated in Table 1.
2 Biological Production of Nanoparticles
Nanoparticle synthesis by biological route is a green chemistry approach that has led
to an exciting new and rational interdisciplinary branch of science with considerable
prospective due to their enriched diversity and cosmopolitan nature. Harnessing the
microorganisms for green NP synthesis is gaining impetus due to ease of synthesis,
eco-friendly in nature, unwavering, non-toxic, efficient, economical route and use
of ambient conditions for NP synthesis (Sastry et al. 2003). Different types of
nanoparticles can be synthesized using biological sources such as plants, arthropods
and various microorganisms such as algae, fungi, yeast, bacteria, actinomycetes
and viruses (Lateef et al. 2016a, b; Thakkar et al. 2010). Various parameters,
such as temperature, pH, time duration, metal ion concentration, culture medium,
biomass and inoculum age, influence the size and shape of the nanoparticle (GuilgerCasagrande and Lima 2009). Wide array of amino acids, peptides, enzymes and
organic acids synthesized by plants and microorganisms stabilizes the biological
formulation of various microbial-mediated nanostructures (Adelere and Lateef 2016;
Lateef et al. 2015a). Furthermore, NPs can be synthesized using various substrates,
and many factors are known to have effects on the biosynthesis of NPs (Camargo
et al. 2009; Vogtle et al. 2009; Swamy et al. 2015, 2018; Rudramurthy et al. 2016;
Rudramurthy and Swamy 2018) (Fig. 1).
2.1 Mechanisms of Synthesis of Nanoparticles
from Microorganisms
The actual mechanism of NP synthesis still remains skeptical. It is speculated that,
metal ions are trapped on the surface or inside the cell of an organism and are
N. B. Raj et al.
has thermodynamically controlled chemical compositions than top-down method
(Thakkar et al. 2010).
Physical and chemical methods result in controlled synthesis of NPs and can
yield large amount of NPs in shorter duration (Alkilany et al. 2015; He et al. 2015).
Regardless of the pervasive use of physical and chemical methods for NP synthesis,
growing body of evidences suggests that, there have been emerging issues such as
hazardous procedures, non-biodegradable, cumbersome, capital intensive, energy
intensive, toxic by-products, eutrophication, high monodispersity and requirement
for toxic chemicals, solvents, reducing agents, stabilizers, high temperature, metal
ions, reducing agents, pH and pressure for NP synthesis (Mallick et al. 2004). Hence,
the researchers round the globe are in quest for the ancillary route for efficient and
nature-friendly NP synthesis owing to their advantages as stated in Table 1.
2 Biological Production of Nanoparticles
Nanoparticle synthesis by biological route is a green chemistry approach that has led
to an exciting new and rational interdisciplinary branch of science with considerable
prospective due to their enriched diversity and cosmopolitan nature. Harnessing the
microorganisms for green NP synthesis is gaining impetus due to ease of synthesis,
eco-friendly in nature, unwavering, non-toxic, efficient, economical route and use
of ambient conditions for NP synthesis (Sastry et al. 2003). Different types of
nanoparticles can be synthesized using biological sources such as plants, arthropods
and various microorganisms such as algae, fungi, yeast, bacteria, actinomycetes
and viruses (Lateef et al. 2016a, b; Thakkar et al. 2010). Various parameters,
such as temperature, pH, time duration, metal ion concentration, culture medium,
biomass and inoculum age, influence the size and shape of the nanoparticle (GuilgerCasagrande and Lima 2009). Wide array of amino acids, peptides, enzymes and
organic acids synthesized by plants and microorganisms stabilizes the biological
formulation of various microbial-mediated nanostructures (Adelere and Lateef 2016;
Lateef et al. 2015a). Furthermore, NPs can be synthesized using various substrates,
and many factors are known to have effects on the biosynthesis of NPs (Camargo
et al. 2009; Vogtle et al. 2009; Swamy et al. 2015, 2018; Rudramurthy et al. 2016;
Rudramurthy and Swamy 2018) (Fig. 1).
2.1 Mechanisms of Synthesis of Nanoparticles
from Microorganisms
The actual mechanism of NP synthesis still remains skeptical. It is speculated that,
metal ions are trapped on the surface or inside the cell of an organism and are