Precision Microbial Nanobiosynthesis: Knowledge …
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concentration; (ii) precursor(s) concentration(s); (iii) pH; and (iv) temperature. For
instance, it is widely known that environmental factors including carbon source,
pH, and temperature can strongly influence the composition of the fungal secretome
(McCotter et al. 2016).
Fungal secretome include all the proteins and enzymes secrete by fungi, for either
anchored to the cell surface or freed in the extracellular environment. Fungal secretome have been already investigated for promising biotechnological applications,
including fungi-mediated biosynthesis of nanoparticles (see Sect. 3). The optimal
conditions for the extracellular reduction of SeO 2 to Se
0 for SeNPs synthesis in the
culture broth of the fungus Trichoderma WL-Go have been recently investigated by
Diko et al. (2020). As reported in many works for different microorganisms, optimal
conditions for nanoparticles synthesis not always match with optimal conditions for
microbial growth. One example has been provided by the results obtained from a
study aimed to the identification of the optimal conditions of pH, temperature, and
NaCl concentration the bacterium P. aeruginosa RB to achieve high purity and high
synthesis rate for CdSe NPs synthesis (Ayano et al. 2015). Brooks and Lefebvre
(2017) have defined the optimal culture conditions for CdSe quantum dots (CdSe
QDs) synthesis by the yeast Saccharomyces cerevisiae BY4742. The CdSe QDs
have been produced most efficiently when S. cerevisiae cells enter into the stationary
phase, incubated for 6 h in 1 mM selenite and then incubated in fresh growth medium
containing 3 mM Cd (II). The maximum of CdSe QDs synthesis was reached at 84 h,
resulting in an increased CdSe QDs production of 70% respect to the previous works
(Brooks and Lefebvre 2017).
The work reported by Voeikova et al. (2018) has highlighted how the composition
of the nutrient medium could affect the efficiency of Ag 2 S NPs biosynthesis using the
bacterium Shewanella oneidensis MR-1. Through the use of 10 mM concentrations
for both the precursors AgNO 3 and Na 2 S 2 O 3 and the elimination of cell washing
step after the cells have grown in rich nutrient media, the production yield value
has increased up to 50–60% compared to 15–20% of a previous described protocol
(Voeikova et al. 2018). The effects of precursor concentration, temperature, and pH
of the culture supernatant on AgNPs synthesis and particle sizes have been also
described by Gurunathan et al. (2009) for E. coli strain DH5α. The optimal condition of 5 mM concentration of Ag
+ ions, temperature of 60 °C, pH 10 have shown
the maximum synthesis of AgNPs through reduction of Ag
+ ions by the culture
supernatant of E. coli DH5α.
Chen et al. (2017) have highlighted the relationships between changes in precursor
concentration and pH and the AgNPs biosynthesis in D. radiodurans, highlighting
how the tuning of such specific abiotic factors could provide control over nanoparticles morphology, composition, size, and production yield. In particular, the stationary
phase culture of D. radiodurans exposed for 2 h to 0.1 and 0.5 mM AgNO 3 has shown
about 2-times increase in AgNPs production yield compared to the control. When
the pH of the supernatant was increased from 7 to 9, the AgNPs production is also
increased by about 4 times. These results have shown that tuning of specific environmental stressors could provide control over morphology, composition, and size
of nanoparticles synthesized by D. radiodurans (Chen et al. 2017).
83
concentration; (ii) precursor(s) concentration(s); (iii) pH; and (iv) temperature. For
instance, it is widely known that environmental factors including carbon source,
pH, and temperature can strongly influence the composition of the fungal secretome
(McCotter et al. 2016).
Fungal secretome include all the proteins and enzymes secrete by fungi, for either
anchored to the cell surface or freed in the extracellular environment. Fungal secretome have been already investigated for promising biotechnological applications,
including fungi-mediated biosynthesis of nanoparticles (see Sect. 3). The optimal
conditions for the extracellular reduction of SeO 2 to Se
0 for SeNPs synthesis in the
culture broth of the fungus Trichoderma WL-Go have been recently investigated by
Diko et al. (2020). As reported in many works for different microorganisms, optimal
conditions for nanoparticles synthesis not always match with optimal conditions for
microbial growth. One example has been provided by the results obtained from a
study aimed to the identification of the optimal conditions of pH, temperature, and
NaCl concentration the bacterium P. aeruginosa RB to achieve high purity and high
synthesis rate for CdSe NPs synthesis (Ayano et al. 2015). Brooks and Lefebvre
(2017) have defined the optimal culture conditions for CdSe quantum dots (CdSe
QDs) synthesis by the yeast Saccharomyces cerevisiae BY4742. The CdSe QDs
have been produced most efficiently when S. cerevisiae cells enter into the stationary
phase, incubated for 6 h in 1 mM selenite and then incubated in fresh growth medium
containing 3 mM Cd (II). The maximum of CdSe QDs synthesis was reached at 84 h,
resulting in an increased CdSe QDs production of 70% respect to the previous works
(Brooks and Lefebvre 2017).
The work reported by Voeikova et al. (2018) has highlighted how the composition
of the nutrient medium could affect the efficiency of Ag 2 S NPs biosynthesis using the
bacterium Shewanella oneidensis MR-1. Through the use of 10 mM concentrations
for both the precursors AgNO 3 and Na 2 S 2 O 3 and the elimination of cell washing
step after the cells have grown in rich nutrient media, the production yield value
has increased up to 50–60% compared to 15–20% of a previous described protocol
(Voeikova et al. 2018). The effects of precursor concentration, temperature, and pH
of the culture supernatant on AgNPs synthesis and particle sizes have been also
described by Gurunathan et al. (2009) for E. coli strain DH5α. The optimal condition of 5 mM concentration of Ag
+ ions, temperature of 60 °C, pH 10 have shown
the maximum synthesis of AgNPs through reduction of Ag
+ ions by the culture
supernatant of E. coli DH5α.
Chen et al. (2017) have highlighted the relationships between changes in precursor
concentration and pH and the AgNPs biosynthesis in D. radiodurans, highlighting
how the tuning of such specific abiotic factors could provide control over nanoparticles morphology, composition, size, and production yield. In particular, the stationary
phase culture of D. radiodurans exposed for 2 h to 0.1 and 0.5 mM AgNO 3 has shown
about 2-times increase in AgNPs production yield compared to the control. When
the pH of the supernatant was increased from 7 to 9, the AgNPs production is also
increased by about 4 times. These results have shown that tuning of specific environmental stressors could provide control over morphology, composition, and size
of nanoparticles synthesized by D. radiodurans (Chen et al. 2017).