Precision Microbial Nanobiosynthesis: Knowledge …
85
yellow, green, and blue light at 300 μmol photons m
−2 s
−1 can affect valve thickness, Si concentration, frustule diameter, foramen characteristics. All these morphological changes influence photonic properties of frustules (Su et al. 2015, 2017,
2018b). Although the controlling of biomineralization process remains a challenge,
these results could have important implication on the development of light-based
modification methods of diatom frustules. The effect on diatom frustules properties
(e.g., pore sizes and pore density) has been also explored by changing operational
parameters of experimental setup and abiotic factors as pH, salinity, pH, temperature, nutrient concentration, and precursor Si(OH) 4 concentration (Su et al. 2018a).
Townley et al. (2007) have reported alteration in pore sizes of Coscinodiscus wailesii
frustules when exposed to sublethal concentration of Ni. In diatoms, the possibility
of in vivo doping of frustules has been described through the addition of sublethal
concentrations of given precursors to the culture medium. For instance, the doping of
diatom Pinnularia sp. frustules or diatoms Thalassiosira weissflogii frustules with
titania (TiO 2 ) has been reported (Jeffryes et al. 2008a; Lang et al. 2013) as well
as the nanobiosynthesis of frustules containing Si–Ge oxides nanocomb in diatoms
Nitzschia and Pinnularia by adding Ge(OH) 4 or GeO 2 in the culture medium (Rorrer
et al. 2005; Qin et al. 2008; Jeffryes et al. 2008b, c).
The costs of culture media for microbial growth should be seriously considered
not to limit the future large-scale productions of microbial biosynthetic nanomaterials. A notable example is bacterial nanocellulose whose application in biomedical
field is still limited, mainly because of culture medium costs (Jacek et al. 2019a)
and low bacterial nanocellulose production yield. Chandrasekaran et al. (2017) have
reported a yield enhancement of bacterial nanocellulose synthesis in Gluconobacter
xylinus cultured in Super Optimal Broth, with a 50% conversion of the carbon
source to bacterial nanocellulose, compared to a 7% conversion in the traditional
Hestrin-Schramm medium. Several researches have attempted to produce bacterial
nanocellulose from various alternative low-cost substrates using agro-wastes industrial by-products. This is a case in point of the use of a white biotechnology approach
in microbial nanobiosynthesis, i.e., the microbial conversion of agro-wastes into a
value-added product like bacterial nanocellulose. The results obtained using agrowastes-based low-cost media for the production of bacterial nanocellulose have been
described in some recent works: a low-cost coconut water medium containing 1%
(v/v) acetic acid and 2% (v/v) ethanol for the thermotolerant bacterium K. xylinus
MSKU 12 (Naloka et al. 2020), vinasse 40% culture medium for K. xylinus PTCC
1734 (Barshan et al. 2019), and sugarcane molasses for K. rhaeticus (Machado et al.
2018).
Taken together, these results have provided interesting insight about how bacterial nanocellulose could be synthesized with good production yields using low-cost
media. The production of bacterial magnetosomes is characterized by some drawbacks, including specific microaerophilic growth conditions required, low yield (Yan
et al. (2017) and time-consuming purification steps (Xu et al. 2014). For different
batch, fed-batch, and semi-continuous microbial growth strategies reported in literature, O 2 concentration seemed to be one of the most important abiotic parameters
for bacterial magnetosomes production (Heyen and Schüler 2003; Sun et al. 2008;
85
yellow, green, and blue light at 300 μmol photons m
−2 s
−1 can affect valve thickness, Si concentration, frustule diameter, foramen characteristics. All these morphological changes influence photonic properties of frustules (Su et al. 2015, 2017,
2018b). Although the controlling of biomineralization process remains a challenge,
these results could have important implication on the development of light-based
modification methods of diatom frustules. The effect on diatom frustules properties
(e.g., pore sizes and pore density) has been also explored by changing operational
parameters of experimental setup and abiotic factors as pH, salinity, pH, temperature, nutrient concentration, and precursor Si(OH) 4 concentration (Su et al. 2018a).
Townley et al. (2007) have reported alteration in pore sizes of Coscinodiscus wailesii
frustules when exposed to sublethal concentration of Ni. In diatoms, the possibility
of in vivo doping of frustules has been described through the addition of sublethal
concentrations of given precursors to the culture medium. For instance, the doping of
diatom Pinnularia sp. frustules or diatoms Thalassiosira weissflogii frustules with
titania (TiO 2 ) has been reported (Jeffryes et al. 2008a; Lang et al. 2013) as well
as the nanobiosynthesis of frustules containing Si–Ge oxides nanocomb in diatoms
Nitzschia and Pinnularia by adding Ge(OH) 4 or GeO 2 in the culture medium (Rorrer
et al. 2005; Qin et al. 2008; Jeffryes et al. 2008b, c).
The costs of culture media for microbial growth should be seriously considered
not to limit the future large-scale productions of microbial biosynthetic nanomaterials. A notable example is bacterial nanocellulose whose application in biomedical
field is still limited, mainly because of culture medium costs (Jacek et al. 2019a)
and low bacterial nanocellulose production yield. Chandrasekaran et al. (2017) have
reported a yield enhancement of bacterial nanocellulose synthesis in Gluconobacter
xylinus cultured in Super Optimal Broth, with a 50% conversion of the carbon
source to bacterial nanocellulose, compared to a 7% conversion in the traditional
Hestrin-Schramm medium. Several researches have attempted to produce bacterial
nanocellulose from various alternative low-cost substrates using agro-wastes industrial by-products. This is a case in point of the use of a white biotechnology approach
in microbial nanobiosynthesis, i.e., the microbial conversion of agro-wastes into a
value-added product like bacterial nanocellulose. The results obtained using agrowastes-based low-cost media for the production of bacterial nanocellulose have been
described in some recent works: a low-cost coconut water medium containing 1%
(v/v) acetic acid and 2% (v/v) ethanol for the thermotolerant bacterium K. xylinus
MSKU 12 (Naloka et al. 2020), vinasse 40% culture medium for K. xylinus PTCC
1734 (Barshan et al. 2019), and sugarcane molasses for K. rhaeticus (Machado et al.
2018).
Taken together, these results have provided interesting insight about how bacterial nanocellulose could be synthesized with good production yields using low-cost
media. The production of bacterial magnetosomes is characterized by some drawbacks, including specific microaerophilic growth conditions required, low yield (Yan
et al. (2017) and time-consuming purification steps (Xu et al. 2014). For different
batch, fed-batch, and semi-continuous microbial growth strategies reported in literature, O 2 concentration seemed to be one of the most important abiotic parameters
for bacterial magnetosomes production (Heyen and Schüler 2003; Sun et al. 2008;