Applications of Microbe-Based Nanoparticles …
349
Effect of PH
Variation in pH can regulate the size and shape of the nanoparticle as shown by
Gericke and Pinches (2006) in Verticillium luteoalbum. At pH 3, spherical-shaped
(<10.0 nm) NPs were synthesized. However, the size of the NPs increased with
well-defined shapes such as hexagons, triangles, rods and spheres up to pH 5.0. At
pH 7 and 9, small spherical as well as bigger particles with irregular and undefined
shapes were obtained (Gericke and Pinches 2006; Karbasian et al. 2008). Das et al.
(2012) reported that, pH influenced AuNPs synthesis in Rhizopus oryzae. At pH 7,
the size of the gold nanoparticles was 26 nm, whereas 250 nm were obtained at pH
2.0. Further, they observed that maximum stability was obtained at neutral, basic and
slightly acidic conditions, respectively. Similar results were reported in Penicillium
oxalicum (Du et al. 2015). Concordant results are reported for AgNPs synthesis in
several other fungi such as Epicoccum nigrum, an endophytic fungus (Qian et al.
2013), Colleotrichum sp. ALF2 (Azmath et al. 2016), Fusarium oxysporum (Birla
et al. 2013), Aspergillus oryzae MTCC 1846 (Phanjom and Ahmed 2017), Aspergillus
fumigatus BTCB10 (Shahzad et al. 2019), Isaria fumosorosea (Banu and Balasubramanian 2014), Arthroderma fulvum (Xue et al. 2016), and Sclerotinia sclerotiorum
MTCC 8785 (Saxena et al. 2016).
In another study, modulation of initial pH (5, 8 and 10) in the fungal extract of
Aspergillus terreus IF0 resulted in elongated-, triangular- and rod-shaped AuNPs.
Size range of 10–19 nm AuNPs was obtained at pH 10 (Priyadarshini et al. 2014).
Growing body of evidences has shown that microbial-based nanoparticles are also
synthesized at neutral or slightly alkaline pH. Balakumaran et al. (2015) obtained
well-dispersed and extremely stable 5–30 nm sized, spherical-shaped AgNPs at pH
7 using the endophytic fungus, Guignardia mangiferae. In another study, maximum
production of AgNPs was achieved at pH 7.2 with a concentration of 136 ppm using
Penicillium oxalicum GRS-1. The AgNPs obtained was spherical in shape with size
ranging from 10 to 40 nm (Rose et al. 2019). Similarly, Penicillium purpurogenum
synthesized spherical-shaped 8–10 nm size AgNPs at pH 8 (Nayak et al. 2011).
Optimum pH for extracellular synthesis of AgNPs synthesized from a marine fungus,
Penicillium fellutanum, was found to be pH 6 (Kathiresan et al. 2009).
Tidke et al. (2014) studied the influence of different pH on extracellular synthesis
of AuNPs in the fungus Fusarium acuminatum. Results indicated that, pH from 5 to
7 favored the AuNPs synthesis with a particle size of 8–28 nm with average size of
17 nm. In another study, pH ranging from 7 to 11 was found to be optimum for AuNPs
synthesis in Trichoderma sp. WL-Go (Qu et al. 2016). Optimum AuNPs synthesis
was observed by various workers at neutral and alkaline pH (Mishra et al. 2011a).
Synthesis of AuNPs using Shewanella algae under anaerobic condition was studied
by Konishi et al. (2007). Results suggest that, 10–20 nm of AuNPs was obtained
in periplasmic space at pH 7.0, while size of 15–200 nm on the surface at pH 2.8.
Mishra et al. (2011b) reported that at pH 2, a highly acidic condition did not favor
the synthesis of AuNPs in Penicillium brevicompactum. However, maximum yield
and a size of 100 nm were observed at pH 6 and 8. Beyond pH 8, slight increase
in the size (200 nm) and decrease in AuNPs synthesis was observed. Also, purified
349
Effect of PH
Variation in pH can regulate the size and shape of the nanoparticle as shown by
Gericke and Pinches (2006) in Verticillium luteoalbum. At pH 3, spherical-shaped
(<10.0 nm) NPs were synthesized. However, the size of the NPs increased with
well-defined shapes such as hexagons, triangles, rods and spheres up to pH 5.0. At
pH 7 and 9, small spherical as well as bigger particles with irregular and undefined
shapes were obtained (Gericke and Pinches 2006; Karbasian et al. 2008). Das et al.
(2012) reported that, pH influenced AuNPs synthesis in Rhizopus oryzae. At pH 7,
the size of the gold nanoparticles was 26 nm, whereas 250 nm were obtained at pH
2.0. Further, they observed that maximum stability was obtained at neutral, basic and
slightly acidic conditions, respectively. Similar results were reported in Penicillium
oxalicum (Du et al. 2015). Concordant results are reported for AgNPs synthesis in
several other fungi such as Epicoccum nigrum, an endophytic fungus (Qian et al.
2013), Colleotrichum sp. ALF2 (Azmath et al. 2016), Fusarium oxysporum (Birla
et al. 2013), Aspergillus oryzae MTCC 1846 (Phanjom and Ahmed 2017), Aspergillus
fumigatus BTCB10 (Shahzad et al. 2019), Isaria fumosorosea (Banu and Balasubramanian 2014), Arthroderma fulvum (Xue et al. 2016), and Sclerotinia sclerotiorum
MTCC 8785 (Saxena et al. 2016).
In another study, modulation of initial pH (5, 8 and 10) in the fungal extract of
Aspergillus terreus IF0 resulted in elongated-, triangular- and rod-shaped AuNPs.
Size range of 10–19 nm AuNPs was obtained at pH 10 (Priyadarshini et al. 2014).
Growing body of evidences has shown that microbial-based nanoparticles are also
synthesized at neutral or slightly alkaline pH. Balakumaran et al. (2015) obtained
well-dispersed and extremely stable 5–30 nm sized, spherical-shaped AgNPs at pH
7 using the endophytic fungus, Guignardia mangiferae. In another study, maximum
production of AgNPs was achieved at pH 7.2 with a concentration of 136 ppm using
Penicillium oxalicum GRS-1. The AgNPs obtained was spherical in shape with size
ranging from 10 to 40 nm (Rose et al. 2019). Similarly, Penicillium purpurogenum
synthesized spherical-shaped 8–10 nm size AgNPs at pH 8 (Nayak et al. 2011).
Optimum pH for extracellular synthesis of AgNPs synthesized from a marine fungus,
Penicillium fellutanum, was found to be pH 6 (Kathiresan et al. 2009).
Tidke et al. (2014) studied the influence of different pH on extracellular synthesis
of AuNPs in the fungus Fusarium acuminatum. Results indicated that, pH from 5 to
7 favored the AuNPs synthesis with a particle size of 8–28 nm with average size of
17 nm. In another study, pH ranging from 7 to 11 was found to be optimum for AuNPs
synthesis in Trichoderma sp. WL-Go (Qu et al. 2016). Optimum AuNPs synthesis
was observed by various workers at neutral and alkaline pH (Mishra et al. 2011a).
Synthesis of AuNPs using Shewanella algae under anaerobic condition was studied
by Konishi et al. (2007). Results suggest that, 10–20 nm of AuNPs was obtained
in periplasmic space at pH 7.0, while size of 15–200 nm on the surface at pH 2.8.
Mishra et al. (2011b) reported that at pH 2, a highly acidic condition did not favor
the synthesis of AuNPs in Penicillium brevicompactum. However, maximum yield
and a size of 100 nm were observed at pH 6 and 8. Beyond pH 8, slight increase
in the size (200 nm) and decrease in AuNPs synthesis was observed. Also, purified