Precision Microbial Nanobiosynthesis: Knowledge …
91
4 Genetic Engineering and Synthetic Biology: From
a Deeper Knowledge in Microbial Nanobiosynthesis
to the Construction of Microbial ‘Nanofactories’
For a proper scale-up of the microbial nanobiosynthesis processes that make microbial nanobiosynthesis industrially worthwhile, further steps to solve some key drawbacks will be required. One of these drawbacks is the inhomogeneity in the size and
the shape of microbial-synthesized nanoparticles often reported in literature. Dispersity, i.e., the size distribution of the nanoparticle population as well as their shape
of bionanoparticles of microbial origin, is key properties that strongly influence
the nanoparticle’s behavior in fluids but also their electronic and optical properties. Thus, the control over dispersity and shape is fundamental not to limit future
applications of these fascinating materials. As described in Sect. 2, focused changes
in culture conditions, optimization and standardization of microbial culture growth
protocols can strongly contribute to the control, tuning, and to the improvement of
biosynthesized microbial nanomaterials.
Today, genetic engineering techniques provide very powerful tools to enhance the
performance of microbiological-based producing systems, while providing the identification of involved biochemical entities as well as a more complete knowledge
of metabolic networks and controlling factors involved in microbial nanobiosynthesis. The main results of research concerning the application of genetic engineering
to microbial nanobiosynthesis are summarized in Table 3. Wide arrays of genetic
engineering toolbox for gene expression control are now available. Genetic techniques like gene silencing and gene deletion that enable the downregulation of gene
expression can be useful for the identification of the specific role of a given gene(s)
and gene(s)-encoded product(s) (proteins and/or enzymes) in microbial nanobiosynthesis. Thus, these genetic approaches can be very useful for the elucidation of
metabolic pathways involved in microbial nanobiosythesis.
4.1 Microbial Synthesis of Metal Nanoparticles by Mutant
and Engineered Cells
The silver-resistant strain and AgNPs producer E. coli 116AR have been isolated
and studied by Lin et al. (2014). The deletion mutation of the gene encoding NapC
(napC), the membrane-anchored tetra-heme c-type cytochrome subunit of the
periplasmic nitrate reductase has resulted in a marked decrease in the cellular AgNPs
accumulation, thus allowing to identify the molecular mechanism behind the AgNPs
biosynthesis in E. coli 116AR (Lin et al. 2014). A novel aerobic selenite reductase
CsrF able to form Se(0) and Cr(III) NPs in the bacterium Alishewanella WH16-1
has been identified through the csrF gene disruption (Xia et al. 2018). In addition to
gene silencing and gene deletion, gene overexpression strategies are equally powerful
genetic engineering tool to identify biochemical pathways underlying microbial
91
4 Genetic Engineering and Synthetic Biology: From
a Deeper Knowledge in Microbial Nanobiosynthesis
to the Construction of Microbial ‘Nanofactories’
For a proper scale-up of the microbial nanobiosynthesis processes that make microbial nanobiosynthesis industrially worthwhile, further steps to solve some key drawbacks will be required. One of these drawbacks is the inhomogeneity in the size and
the shape of microbial-synthesized nanoparticles often reported in literature. Dispersity, i.e., the size distribution of the nanoparticle population as well as their shape
of bionanoparticles of microbial origin, is key properties that strongly influence
the nanoparticle’s behavior in fluids but also their electronic and optical properties. Thus, the control over dispersity and shape is fundamental not to limit future
applications of these fascinating materials. As described in Sect. 2, focused changes
in culture conditions, optimization and standardization of microbial culture growth
protocols can strongly contribute to the control, tuning, and to the improvement of
biosynthesized microbial nanomaterials.
Today, genetic engineering techniques provide very powerful tools to enhance the
performance of microbiological-based producing systems, while providing the identification of involved biochemical entities as well as a more complete knowledge
of metabolic networks and controlling factors involved in microbial nanobiosynthesis. The main results of research concerning the application of genetic engineering
to microbial nanobiosynthesis are summarized in Table 3. Wide arrays of genetic
engineering toolbox for gene expression control are now available. Genetic techniques like gene silencing and gene deletion that enable the downregulation of gene
expression can be useful for the identification of the specific role of a given gene(s)
and gene(s)-encoded product(s) (proteins and/or enzymes) in microbial nanobiosynthesis. Thus, these genetic approaches can be very useful for the elucidation of
metabolic pathways involved in microbial nanobiosythesis.
4.1 Microbial Synthesis of Metal Nanoparticles by Mutant
and Engineered Cells
The silver-resistant strain and AgNPs producer E. coli 116AR have been isolated
and studied by Lin et al. (2014). The deletion mutation of the gene encoding NapC
(napC), the membrane-anchored tetra-heme c-type cytochrome subunit of the
periplasmic nitrate reductase has resulted in a marked decrease in the cellular AgNPs
accumulation, thus allowing to identify the molecular mechanism behind the AgNPs
biosynthesis in E. coli 116AR (Lin et al. 2014). A novel aerobic selenite reductase
CsrF able to form Se(0) and Cr(III) NPs in the bacterium Alishewanella WH16-1
has been identified through the csrF gene disruption (Xia et al. 2018). In addition to
gene silencing and gene deletion, gene overexpression strategies are equally powerful
genetic engineering tool to identify biochemical pathways underlying microbial