Applications of Microbe-Based Nanoparticles …
353
sized rods (12%), triangle (30%), hexagonal (7%), pyramids (5%) and stars (2%)
were observed. Further, polydispersed spherical-shaped particles had size range of
2–70 nm, and the rods averaged 12–15 nm, the hexagons with 30–42 nm, the triangles
with 25–40 and 5–20 nm in star-shaped were obtained (Kumar et al. 2008). Algal
extract of Turbinaria conoides was used to synthesize small spherical-, triangleand pseudo-spherical-shaped particles AuNPs having 6–10 nm size using 1 mM
aqueous solution of gold chloride at room temperature for 24 h (Rajeshkumar et al.
2013). Similarly, in Calothrix algae, 0.1 mm AuCl 4 solution was used to synthesize
truncated-, triangular- and spherical-shaped AuNPs in the size range of 30–120 nm
at 22–25 °C for 3 days (Kumar et al. 2016). Thus, concentration of precursors can
influence the formation of nanoparticles with defined effects on size and morphology.
Effect of Enzymes
Extracellular enzymes produced by microorganisms are well documented and play
an important role as reducing agents in the production of nanoparticles. Increasing
body of evidences suggests that, the cofactors such as nicotinamide adenine dinucleotide (NADH) and reduced form of Nicotinamide adenine dinucleotide phosphate (NADPH)-dependent enzymes act as reducing agents and transfer the electrons
from NADH by NADH-reliant enzymes, which act electron carriers (Zomorodian
et al. 2016; Baymiller et al. 2017). Extracellular synthesis of AuNPs by R. capsulata was achieved by the reduction of gold by NADH-reliant reductase enzymes
(He et al. 2007). Similar enzyme machinery was used to synthesize AuNPs in
Stenotrophomonas maltophilia (Nangia et al. 2009). Sanghi et al. (2011) reported
that P. chrysosporium synthesized extracellular AuNPs using laccase enzyme and
intracellularly by ligninase within 90 min at 37 °C. Ahmad et al. (2002) reported that
F. oxysporum synthesized CdS nanoparticles via extracellular secretion of sulfate
reductases enzyme (Table 2).
Likewise, Gholami-Shabani et al. (2015) and Gholami-Shabani et al. (2016)
synthesized AuNPs using sulfite oxidoreductase enzyme in Escherichia coli and
Fusarium oxysporum. In yet another study by Gholami-Shabani et al. (2014), AgNPs
were synthesized from Fusarium oxysporum using the enzyme nitrate reductase.
Similar studies on AgNPs synthesis using the enzyme nitrate reductase and quinones
were documented in Sclerotium rolfsii (Narayanan et al. 2011), Fusarium oxysporum (Kumar et al. 2007a, b; Hamedia et al. 2017), Bacillus clausii (Mukherjee
et al. 2018), B. subtilis (Saifuddin et al. 2009), E. coli (Gurunathan et al. 2009),
Pseudomonas aeruginosa (Kumar and Mamidyala Kumar and Mamidyala 2011a, b)
and in Bacillus cereus strain HMH1 for magnetic iron oxide nanoparticle synthesis
(Fatemi et al. 2018). Also, lignin peroxidase enzyme was used in the synthesis of
spherical crystalline AuNPs (10 ± 2 nm) and amorphous-shaped SeNPs (100 ±
10 nm) in Acinetobacter sp. SW30 (Wadhwani et al. 2017). These studies established roles being played by different enzymes in the biosynthesis of nanoparticles;
thus, their modulation would influence the generation of nanoparticles.
353
sized rods (12%), triangle (30%), hexagonal (7%), pyramids (5%) and stars (2%)
were observed. Further, polydispersed spherical-shaped particles had size range of
2–70 nm, and the rods averaged 12–15 nm, the hexagons with 30–42 nm, the triangles
with 25–40 and 5–20 nm in star-shaped were obtained (Kumar et al. 2008). Algal
extract of Turbinaria conoides was used to synthesize small spherical-, triangleand pseudo-spherical-shaped particles AuNPs having 6–10 nm size using 1 mM
aqueous solution of gold chloride at room temperature for 24 h (Rajeshkumar et al.
2013). Similarly, in Calothrix algae, 0.1 mm AuCl 4 solution was used to synthesize
truncated-, triangular- and spherical-shaped AuNPs in the size range of 30–120 nm
at 22–25 °C for 3 days (Kumar et al. 2016). Thus, concentration of precursors can
influence the formation of nanoparticles with defined effects on size and morphology.
Effect of Enzymes
Extracellular enzymes produced by microorganisms are well documented and play
an important role as reducing agents in the production of nanoparticles. Increasing
body of evidences suggests that, the cofactors such as nicotinamide adenine dinucleotide (NADH) and reduced form of Nicotinamide adenine dinucleotide phosphate (NADPH)-dependent enzymes act as reducing agents and transfer the electrons
from NADH by NADH-reliant enzymes, which act electron carriers (Zomorodian
et al. 2016; Baymiller et al. 2017). Extracellular synthesis of AuNPs by R. capsulata was achieved by the reduction of gold by NADH-reliant reductase enzymes
(He et al. 2007). Similar enzyme machinery was used to synthesize AuNPs in
Stenotrophomonas maltophilia (Nangia et al. 2009). Sanghi et al. (2011) reported
that P. chrysosporium synthesized extracellular AuNPs using laccase enzyme and
intracellularly by ligninase within 90 min at 37 °C. Ahmad et al. (2002) reported that
F. oxysporum synthesized CdS nanoparticles via extracellular secretion of sulfate
reductases enzyme (Table 2).
Likewise, Gholami-Shabani et al. (2015) and Gholami-Shabani et al. (2016)
synthesized AuNPs using sulfite oxidoreductase enzyme in Escherichia coli and
Fusarium oxysporum. In yet another study by Gholami-Shabani et al. (2014), AgNPs
were synthesized from Fusarium oxysporum using the enzyme nitrate reductase.
Similar studies on AgNPs synthesis using the enzyme nitrate reductase and quinones
were documented in Sclerotium rolfsii (Narayanan et al. 2011), Fusarium oxysporum (Kumar et al. 2007a, b; Hamedia et al. 2017), Bacillus clausii (Mukherjee
et al. 2018), B. subtilis (Saifuddin et al. 2009), E. coli (Gurunathan et al. 2009),
Pseudomonas aeruginosa (Kumar and Mamidyala Kumar and Mamidyala 2011a, b)
and in Bacillus cereus strain HMH1 for magnetic iron oxide nanoparticle synthesis
(Fatemi et al. 2018). Also, lignin peroxidase enzyme was used in the synthesis of
spherical crystalline AuNPs (10 ± 2 nm) and amorphous-shaped SeNPs (100 ±
10 nm) in Acinetobacter sp. SW30 (Wadhwani et al. 2017). These studies established roles being played by different enzymes in the biosynthesis of nanoparticles;
thus, their modulation would influence the generation of nanoparticles.