350
N. B. Raj et al.
lignin peroxidase enzyme from Acinetobacter sp. SW 30 was used to synthesize
spherical crystalline AuNPs (10 ± 2 nm particle size) and amorphous SeNPs (100
± 10 nm particle size). The enzyme had maximum activity at pH 2 and temperature of 40 °C (Wadhwani et al. 2017). In addition, Quester et al. (2013) biosynthesized AuNPs using Neurospora crassa at 60 °C under various pH conditions.
Results indicated that AuNPs synthesized displayed different shapes like triangles,
hexagons, pentagons and sizes 10–200, 6–23, 3–12 nm at pH values of 3, 5.5 and 10,
respectively. Shewanella algae synthesized 10–20 nm size AuNPs at pH 7. However,
large size nanoparticles with variable size were observed at lower pH (He et al.
2007; Konishi et al. 2007). Similar results were reported in Enterobacter (Sinha and
Khare 2012). Conversely, contrasting results were reported in Escherichia coli and
Desulfovibrio desulfuricans (Deplanche and Macaskie 2008). These results attest
to the influence of pH on the morphology and sizes of nanoparticles during microbial synthesis, thus necessitating a careful choice of pH for the biofabrication of
nanoparticles.
Effect of Temperature
Temperature plays a pivotal role in controlling the activity of the fungus (Dhillon
et al. 2012). Ahluwalia et al. (2014) synthesized AgNPs with a size range of 51.10 nm
from the culture filtrate of Trichoderma harzianum within 4 h at 40 °C. However,
there was no increase in rate of reaction from 10 to 30 °C. In Fusarium oxysporum,
ideal temperature for AgNPs synthesis was 40–60 °C, and a particle size of 21 and
40 nm was produced (Birla et al. 2013). Phanjom and Ahmed (2017) studied the
influence of different temperature (10, 30, 50, 70 and 90 °C) on AgNPs synthesis
in Aspergillus oryzae MTCC 1846. Results indicated that increase in temperature
affected the particle size and reduced the rate of the AgNPs synthesis. Sphericalshaped AgNPs with particle size of 4–9 nm diameter were obtained at 90 °C within
20 min, whereas the size and rate of the reaction increased from 5 to 24 nm and
up to 6 h with reduction in temperature. According to Xue et al. (2016) in a report
on Arthroderma fulvum, temperature of 55 °C resulted in the synthesis of spherical
AgNPs with a size of 20.56 nm in diameter at the substrate concentration of 1.5 mM,
alkaline pH and reaction time of 10 h. Saxena et al. (2016) also observed temperature
of 80 °C resulted in enhanced spherical-shaped AgNPs synthesis with a range of 10–
15 nm in size in Sclerotinia sclerotiorum MTCC 8785. In Rhizopus stolonifer, AgNPs
with size of 2.86, 25.89 and 48.43 nm were synthesized at various temperatures of
40, 20 and 60 °C (Abdel Rahim et al. 2017). According to Shahzad et al. (2019),
Aspergillus fumigatus BTCB10 synthesized AgNPs of 322.8 nm at 25 °C and the
size increased to 1073.45 nm at 55 °C.
Spheroidal AuNPs with a diameter ranging between 5 and 10 nm at 75 and 100 °C
were synthesized using the culture filtrate of phytopathogenic fungus Botrytis cinerea
(Castro et al. 2013). Spherical- and polycrystalline-shaped, 15–40 nm-sized AuNPs
were synthesized in Gordonia amarae using 2 mM chloroauric acid (HAuCl 4 ) at
pH 10.0 and 90 °C for 20 min (Bennur et al. 2016). In another study, a spherical-,
N. B. Raj et al.
lignin peroxidase enzyme from Acinetobacter sp. SW 30 was used to synthesize
spherical crystalline AuNPs (10 ± 2 nm particle size) and amorphous SeNPs (100
± 10 nm particle size). The enzyme had maximum activity at pH 2 and temperature of 40 °C (Wadhwani et al. 2017). In addition, Quester et al. (2013) biosynthesized AuNPs using Neurospora crassa at 60 °C under various pH conditions.
Results indicated that AuNPs synthesized displayed different shapes like triangles,
hexagons, pentagons and sizes 10–200, 6–23, 3–12 nm at pH values of 3, 5.5 and 10,
respectively. Shewanella algae synthesized 10–20 nm size AuNPs at pH 7. However,
large size nanoparticles with variable size were observed at lower pH (He et al.
2007; Konishi et al. 2007). Similar results were reported in Enterobacter (Sinha and
Khare 2012). Conversely, contrasting results were reported in Escherichia coli and
Desulfovibrio desulfuricans (Deplanche and Macaskie 2008). These results attest
to the influence of pH on the morphology and sizes of nanoparticles during microbial synthesis, thus necessitating a careful choice of pH for the biofabrication of
nanoparticles.
Effect of Temperature
Temperature plays a pivotal role in controlling the activity of the fungus (Dhillon
et al. 2012). Ahluwalia et al. (2014) synthesized AgNPs with a size range of 51.10 nm
from the culture filtrate of Trichoderma harzianum within 4 h at 40 °C. However,
there was no increase in rate of reaction from 10 to 30 °C. In Fusarium oxysporum,
ideal temperature for AgNPs synthesis was 40–60 °C, and a particle size of 21 and
40 nm was produced (Birla et al. 2013). Phanjom and Ahmed (2017) studied the
influence of different temperature (10, 30, 50, 70 and 90 °C) on AgNPs synthesis
in Aspergillus oryzae MTCC 1846. Results indicated that increase in temperature
affected the particle size and reduced the rate of the AgNPs synthesis. Sphericalshaped AgNPs with particle size of 4–9 nm diameter were obtained at 90 °C within
20 min, whereas the size and rate of the reaction increased from 5 to 24 nm and
up to 6 h with reduction in temperature. According to Xue et al. (2016) in a report
on Arthroderma fulvum, temperature of 55 °C resulted in the synthesis of spherical
AgNPs with a size of 20.56 nm in diameter at the substrate concentration of 1.5 mM,
alkaline pH and reaction time of 10 h. Saxena et al. (2016) also observed temperature
of 80 °C resulted in enhanced spherical-shaped AgNPs synthesis with a range of 10–
15 nm in size in Sclerotinia sclerotiorum MTCC 8785. In Rhizopus stolonifer, AgNPs
with size of 2.86, 25.89 and 48.43 nm were synthesized at various temperatures of
40, 20 and 60 °C (Abdel Rahim et al. 2017). According to Shahzad et al. (2019),
Aspergillus fumigatus BTCB10 synthesized AgNPs of 322.8 nm at 25 °C and the
size increased to 1073.45 nm at 55 °C.
Spheroidal AuNPs with a diameter ranging between 5 and 10 nm at 75 and 100 °C
were synthesized using the culture filtrate of phytopathogenic fungus Botrytis cinerea
(Castro et al. 2013). Spherical- and polycrystalline-shaped, 15–40 nm-sized AuNPs
were synthesized in Gordonia amarae using 2 mM chloroauric acid (HAuCl 4 ) at
pH 10.0 and 90 °C for 20 min (Bennur et al. 2016). In another study, a spherical-,