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T. I. Shaheen et al.
Ag-NPs. While the free amino acid groups possibly served as a capping agent for
Ag-NPs.
Jain et al. (2011) reported a two-step presumptive mechanism for mycosynthesis
of Ag-NPs. In the first step, the reduction of bulk silver ions to silver nanoparticles
was done by a 32 kDa protein, which might be a reductase secreted by A. flavus. In
the latter step, Ag-NPs were covered by a 35 kDa protein of enzyme that capped NPs
and confers stability. This phenomenon was confirmed by Durán and Seabra (2012)
that reported the presence of two extracellular proteins with molecular weight of 21
and 24kDa in the biomass filtrate of F. oxysporum during the mycosynthesis of metal
oxide NPs. The actual mechanism of mycosynthesis of NPs, however, is still not
fully understood. According to Mukherjee et al. (2001), in intracellular synthesis,
metal nanoparticles are synthesized below the cell surface, which is probably due to
the metal ions reduction by enzymes present in the cell membrane. Mycosynthesis
proceeds firstly by the metal ions entrapment on the fungal cell surface, which occurs
due to the electrostatic interaction between metal ions and lysine residues (Riddin
et al. 2006). The second step involved reduction of metal ions enzymatically, which
leads to agglomeration and formation of NPs.
The fungal cell wall carbohydrates also play a major role in the metal ions reduction (Yadav et al. 2015). Some researchers suggested a linkage among the size of
mycosynthesized NPs with sub-cellular spot, where the intracellular mycosynthesis
NPs size was smaller than those gained by extracellular means (Ovais et al. 2018).
Because the intracellular approach for NPs synthesis occurred on the fungal cell
wall, the harvest techniques become harsh and hence the expense of NPs mycosynthesis rises (Molnár et al. 2018). Thus, the extracellular approach is believed to be an
important design for NPs mycosynthesis (Qin et al. 2020). Finally, the mechanism of
mycosynthesis of NPs utilizing fungi cells is necessarily needed to be better understood, as the NPs mycosynthesis could be affected by various factors and hence may
lower the reproducibility of the mycosynthesis.
5 Factors That Affect Mycosynthesis of NPs
There are numerous factors that can influence the mycosynthesis process for NPs as
fungal biomass, temperature, precursor concentrations and time contact, pH and the
presence of certain enzymes (Fig. 3). Adjusting the size and shape of metal nanomaterials has been achieved either by controlling of environmental conditions or by
shifting the functional molecules responsible for the reduction, capping and stabilizing NPs (Ma et al. 2017; Mohamed et al. 2019). Improving the reaction conditions
for mycosynthesis of NPs, such as pH, incubation period, aeration, temperature, salt
concentration, mixing ratio, redox conditions and irradiation have been extensively
investigated (Fouda et al. 2018; Liang et al. 2019; Saxena et al. 2016). Size and
shape of NPs depend on the chemical and physical factors during mycosynthesis
which, in turn, influence the orientation of metal clusters during growth leading to
form different shapes with different sizes. Of these factors are the optimum metal
T. I. Shaheen et al.
Ag-NPs. While the free amino acid groups possibly served as a capping agent for
Ag-NPs.
Jain et al. (2011) reported a two-step presumptive mechanism for mycosynthesis
of Ag-NPs. In the first step, the reduction of bulk silver ions to silver nanoparticles
was done by a 32 kDa protein, which might be a reductase secreted by A. flavus. In
the latter step, Ag-NPs were covered by a 35 kDa protein of enzyme that capped NPs
and confers stability. This phenomenon was confirmed by Durán and Seabra (2012)
that reported the presence of two extracellular proteins with molecular weight of 21
and 24kDa in the biomass filtrate of F. oxysporum during the mycosynthesis of metal
oxide NPs. The actual mechanism of mycosynthesis of NPs, however, is still not
fully understood. According to Mukherjee et al. (2001), in intracellular synthesis,
metal nanoparticles are synthesized below the cell surface, which is probably due to
the metal ions reduction by enzymes present in the cell membrane. Mycosynthesis
proceeds firstly by the metal ions entrapment on the fungal cell surface, which occurs
due to the electrostatic interaction between metal ions and lysine residues (Riddin
et al. 2006). The second step involved reduction of metal ions enzymatically, which
leads to agglomeration and formation of NPs.
The fungal cell wall carbohydrates also play a major role in the metal ions reduction (Yadav et al. 2015). Some researchers suggested a linkage among the size of
mycosynthesized NPs with sub-cellular spot, where the intracellular mycosynthesis
NPs size was smaller than those gained by extracellular means (Ovais et al. 2018).
Because the intracellular approach for NPs synthesis occurred on the fungal cell
wall, the harvest techniques become harsh and hence the expense of NPs mycosynthesis rises (Molnár et al. 2018). Thus, the extracellular approach is believed to be an
important design for NPs mycosynthesis (Qin et al. 2020). Finally, the mechanism of
mycosynthesis of NPs utilizing fungi cells is necessarily needed to be better understood, as the NPs mycosynthesis could be affected by various factors and hence may
lower the reproducibility of the mycosynthesis.
5 Factors That Affect Mycosynthesis of NPs
There are numerous factors that can influence the mycosynthesis process for NPs as
fungal biomass, temperature, precursor concentrations and time contact, pH and the
presence of certain enzymes (Fig. 3). Adjusting the size and shape of metal nanomaterials has been achieved either by controlling of environmental conditions or by
shifting the functional molecules responsible for the reduction, capping and stabilizing NPs (Ma et al. 2017; Mohamed et al. 2019). Improving the reaction conditions
for mycosynthesis of NPs, such as pH, incubation period, aeration, temperature, salt
concentration, mixing ratio, redox conditions and irradiation have been extensively
investigated (Fouda et al. 2018; Liang et al. 2019; Saxena et al. 2016). Size and
shape of NPs depend on the chemical and physical factors during mycosynthesis
which, in turn, influence the orientation of metal clusters during growth leading to
form different shapes with different sizes. Of these factors are the optimum metal