Microbial Nanobiotechnology: The Melting Pot …
7
6 What Are on Offer? Microbial Synthesis
of Nanoparticles, Control of Microbes and Applications
in Different Areas of Sub-disciplines of Microbiology
A lot of microorganisms have shown the ability to synthesize exclusive nanostructured materials, like bio-mineralized nanostructures as silicified frustules (Kröger
and Poulsen 2008), calcified coccoliths, magnetosomes (Yan et al. 2017) and organic
nanomaterials like microbial nanocellulose (Hasanin et al. 2018), exopolysaccharide
nanoparticles and bacterial nanowires (Malvankar and Lovley 2012). The microbialmediated biosynthesis of nanomaterials has been extensively explored showing many
advantages and features including: (i) synthesized nanomaterials have defined chemical composition, size and morphology, (ii) biosynthesis is performed at mild physicochemical conditions, (iii) easy handling and cultivation of microbial cells and possibility of cell culture scale-up, (iv) possibility of in vivo tuning nanomaterial characteristics by changing key parameters of cell culture operational set-up or through
genetically engineering tools (Prasad et al. 2016). In order to enable a broad applicability of microbial-mediated biosynthesis of nanomaterials as a real alternative to
‘traditional’ synthetic approaches to nanomanufacturing, many hurdles still need to
be overcome: a reduction of polydispersity of nanoparticles, a more complete characterization of biocapping layer agents, effectiveness of removal procedures of biocapping layer and nanomaterial purifications, standardization of microbial cell culture
protocols for reproducibility of nanosynthesis processes, as well as production costs
and yields.
Overreaching the challenge for the development of reliable eco-friendly nanotechnologies for nanomaterial synthesis is of utmost importance for future exploitations
of broad-impact nanostructured-based technologies and applications, like innovative optical and electrochemical (bio)sensoristic devices and therapeutic and diagnostic applications of nanostructured materials, e.g. for drug delivery, in vivo and
in vitro imaging and development of antimicrobial and anti-tumoral drugs (Kiessling
et al. 2014). The biological synthesis techniques have emerged as the biological
methods of NPs preparation involving the application of different microorganisms
and their enzymes, plant products and extracts derived from animals as shown in
Fig. 3 (Adelere and Lateef 2016; Lateef et al. 2016b; Akintayo et al. 2020). The
natural biogenic metallic nanoparticle synthesis is divided into two categories—(1)
Bioreduction: carried out by the reduction of metal ions into the biologically stable
form using microorganisms and their enzymes. The formed metallic nanostructures
are stable and inert in nature that can be safely separated from contaminated sample;
(2) biosorption carried out using a metal cation in aqueous media allows binding
with organism cell wall that further leads to the formation of stable NPs because
of cell wall or peptide interaction. It has many advantages like cost-effectiveness,
eco-friendly and easy scalability for large-scale production, and does not involve the
use of high pressure, energy, temperature and/or toxic chemicals.
7
6 What Are on Offer? Microbial Synthesis
of Nanoparticles, Control of Microbes and Applications
in Different Areas of Sub-disciplines of Microbiology
A lot of microorganisms have shown the ability to synthesize exclusive nanostructured materials, like bio-mineralized nanostructures as silicified frustules (Kröger
and Poulsen 2008), calcified coccoliths, magnetosomes (Yan et al. 2017) and organic
nanomaterials like microbial nanocellulose (Hasanin et al. 2018), exopolysaccharide
nanoparticles and bacterial nanowires (Malvankar and Lovley 2012). The microbialmediated biosynthesis of nanomaterials has been extensively explored showing many
advantages and features including: (i) synthesized nanomaterials have defined chemical composition, size and morphology, (ii) biosynthesis is performed at mild physicochemical conditions, (iii) easy handling and cultivation of microbial cells and possibility of cell culture scale-up, (iv) possibility of in vivo tuning nanomaterial characteristics by changing key parameters of cell culture operational set-up or through
genetically engineering tools (Prasad et al. 2016). In order to enable a broad applicability of microbial-mediated biosynthesis of nanomaterials as a real alternative to
‘traditional’ synthetic approaches to nanomanufacturing, many hurdles still need to
be overcome: a reduction of polydispersity of nanoparticles, a more complete characterization of biocapping layer agents, effectiveness of removal procedures of biocapping layer and nanomaterial purifications, standardization of microbial cell culture
protocols for reproducibility of nanosynthesis processes, as well as production costs
and yields.
Overreaching the challenge for the development of reliable eco-friendly nanotechnologies for nanomaterial synthesis is of utmost importance for future exploitations
of broad-impact nanostructured-based technologies and applications, like innovative optical and electrochemical (bio)sensoristic devices and therapeutic and diagnostic applications of nanostructured materials, e.g. for drug delivery, in vivo and
in vitro imaging and development of antimicrobial and anti-tumoral drugs (Kiessling
et al. 2014). The biological synthesis techniques have emerged as the biological
methods of NPs preparation involving the application of different microorganisms
and their enzymes, plant products and extracts derived from animals as shown in
Fig. 3 (Adelere and Lateef 2016; Lateef et al. 2016b; Akintayo et al. 2020). The
natural biogenic metallic nanoparticle synthesis is divided into two categories—(1)
Bioreduction: carried out by the reduction of metal ions into the biologically stable
form using microorganisms and their enzymes. The formed metallic nanostructures
are stable and inert in nature that can be safely separated from contaminated sample;
(2) biosorption carried out using a metal cation in aqueous media allows binding
with organism cell wall that further leads to the formation of stable NPs because
of cell wall or peptide interaction. It has many advantages like cost-effectiveness,
eco-friendly and easy scalability for large-scale production, and does not involve the
use of high pressure, energy, temperature and/or toxic chemicals.