Precision Microbial Nanobiosynthesis: Knowledge …
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nanobiosynthesis as well as very useful strategies to increase microbial nanomaterials production yield and/or to control the size and morphological features of
nanomaterials. These gene overexpression strategies can include both homologous
expression in the same original microorganism and heterologous expression in a
different host microorganism.
The study of Shao et al. (2018) has shown how the biosynthesis CdSe QDs can
be improved through the genetic modification of regulation mechanism in the Se
metabolic flux of yeast S. cerevisiae. First, through gene silencing it has been demonstrated that met6 gene encoding methionine synthase involved in the selenocysteineto-selenomethionine pathway regulates the intracellular biosynthesis of CdSe QDs
in yeast S. cerevisiae. Then, the overexpression of the met6 gene in S. cerevisiae cells
has increased CdSe QDs production yield compared to the wild type strain, 41.6 ±
3.1 nmol CdSe QDs per 50 mL of medium and 13.1 ± 3.6 nmol CdSe QDs per
50 mL, respectively (Shao et al. 2018). Elahian et al. (2017) have selected a strain
of the yeast Pichia pastoris with Mut
+ phenotype and they have overexpressed the
cyb5r gene, a metal-resistant gene encoding NADH-cytochrome b5 reductase. The
recombinant P. pastoris has shown the production of stable 70–180 nm-sized spherical AgNPs and SeNPs. In a later paper, Elahian et al. (2020) have used the cyb5r
gene overexpression to produce a recombinant strain of P. pastoris able to biosynthesize 100 nm-sized, monodispersed spherical AuNPs and PdNPs. The maximum
81.23 mg/g Au biosorption capacity was reached only after the first stages of fermentation and the maximum 493.35 mg/g Pd biosorption coincided with trophophase,
i.e., the phase in the active growth of a culture in which primary metabolites are
formed.
The rapid development of genomics in the past decade has broadened boundaries
of biosynthetic and metabolic potential of engineered microorganisms. The heterologous expression using genetically engineered prokaryotic and eukaryotic microbial
hosts has made available cellular biomachineries called ‘microbial chassis’ able
to perform scalable and cost-effective biosynthesis of a wide variety of proteins,
enzymes, pharmaceuticals, therapeutic and industrially valuable products. A ‘microbial chassis’ can be defined as host microorganism that supports both the expression
of the inserted genetic components, like cluster of genes or operons and the function of the genetically encoded biochemical components involved in biosynthetic
pathways of interest for given biotechnological application (Kent and Dixon 2020).
In order to produce improved nanomaterials of microbial origin, the adoption
of suitable microbial chassis could have a remarkable future impact in the field of
metabolic engineering and synthetic biology for microbial nanobiosynthesis. Microbial strains of the model bacterium E. coli with available full sets of genetic manipulation tools have been reported in many works as microbial chassis for the biosynthesis
of nanoparticles. In the recombinant E. coli R189, Kang et al. (2008) have obtained the
intracellular synthesis of fluorescent and water-soluble PC-coated CdSNPs through
the overexpression of the gene coding phytochelatins synthase from the yeast
Schizosaccharomyces pombe and the gene coding γ-glutamylcysteine synthetase,
that synthesize the phytochelatins precursor glutathione. The yeast S. pombe has the
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nanobiosynthesis as well as very useful strategies to increase microbial nanomaterials production yield and/or to control the size and morphological features of
nanomaterials. These gene overexpression strategies can include both homologous
expression in the same original microorganism and heterologous expression in a
different host microorganism.
The study of Shao et al. (2018) has shown how the biosynthesis CdSe QDs can
be improved through the genetic modification of regulation mechanism in the Se
metabolic flux of yeast S. cerevisiae. First, through gene silencing it has been demonstrated that met6 gene encoding methionine synthase involved in the selenocysteineto-selenomethionine pathway regulates the intracellular biosynthesis of CdSe QDs
in yeast S. cerevisiae. Then, the overexpression of the met6 gene in S. cerevisiae cells
has increased CdSe QDs production yield compared to the wild type strain, 41.6 ±
3.1 nmol CdSe QDs per 50 mL of medium and 13.1 ± 3.6 nmol CdSe QDs per
50 mL, respectively (Shao et al. 2018). Elahian et al. (2017) have selected a strain
of the yeast Pichia pastoris with Mut
+ phenotype and they have overexpressed the
cyb5r gene, a metal-resistant gene encoding NADH-cytochrome b5 reductase. The
recombinant P. pastoris has shown the production of stable 70–180 nm-sized spherical AgNPs and SeNPs. In a later paper, Elahian et al. (2020) have used the cyb5r
gene overexpression to produce a recombinant strain of P. pastoris able to biosynthesize 100 nm-sized, monodispersed spherical AuNPs and PdNPs. The maximum
81.23 mg/g Au biosorption capacity was reached only after the first stages of fermentation and the maximum 493.35 mg/g Pd biosorption coincided with trophophase,
i.e., the phase in the active growth of a culture in which primary metabolites are
formed.
The rapid development of genomics in the past decade has broadened boundaries
of biosynthetic and metabolic potential of engineered microorganisms. The heterologous expression using genetically engineered prokaryotic and eukaryotic microbial
hosts has made available cellular biomachineries called ‘microbial chassis’ able
to perform scalable and cost-effective biosynthesis of a wide variety of proteins,
enzymes, pharmaceuticals, therapeutic and industrially valuable products. A ‘microbial chassis’ can be defined as host microorganism that supports both the expression
of the inserted genetic components, like cluster of genes or operons and the function of the genetically encoded biochemical components involved in biosynthetic
pathways of interest for given biotechnological application (Kent and Dixon 2020).
In order to produce improved nanomaterials of microbial origin, the adoption
of suitable microbial chassis could have a remarkable future impact in the field of
metabolic engineering and synthetic biology for microbial nanobiosynthesis. Microbial strains of the model bacterium E. coli with available full sets of genetic manipulation tools have been reported in many works as microbial chassis for the biosynthesis
of nanoparticles. In the recombinant E. coli R189, Kang et al. (2008) have obtained the
intracellular synthesis of fluorescent and water-soluble PC-coated CdSNPs through
the overexpression of the gene coding phytochelatins synthase from the yeast
Schizosaccharomyces pombe and the gene coding γ-glutamylcysteine synthetase,
that synthesize the phytochelatins precursor glutathione. The yeast S. pombe has the