Nanotechnology in Bioprocess Development …
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2014). These microorganisms are able to utilize organic matter such as lignocellulosic wastes, food wastes, municipal wastes, and animal manure during dark fermentation (Han et al. 2011). The application of nanoparticles for the improvement of
dark fermentative biohydrogen production has been reported in several studies as
shown in Table 3. Many of these efforts have yielded positive and desirable results.
A plausible explanation for increased biohydrogen yields is due to the ability of
nanoparticles to improve the process buffering capacity, which in turn stimulates and
enhances the activity of hydrogenase enzymes and substrate hydrolysis (Han et al.
2011). The addition of nanoparticles has shown to enhance the hydrogen-producing
metabolic pathways such as acetate and butyrate reactions, hydrolysis and acidification processes. For instance, the study by Han et al. (2011) supplemented haematite
nanoparticles at 200 mg/L as a bioactive to a bacterial mixed culture (pH 6.0, at
35 °C), and this resulted in a 30% improvement in the hydrogen yield (Table 3). The
authors attributed this increase to enhanced metabolic activities that favour hydrogen
formation pathways (Han et al. 2011).
Furthermore, Wimonsong and Nitisoravut (2015) investigated the activity of nanoporous activated carbon (NAC) in batch fermentative biohydrogen production (using
sucrose-fed anaerobic mixed bacteria culture, at 37 °C). The nanoporous activated
carbon resulted in low concentration of butyric acid with 77% absorption capacity,
thereby increasing the buffering capacity of the system (Wimonsong and Nitisoravut
2015). This invariably improves the physiological state and fermentative activities
of biohydrogen producing microbes that lead to high hydrogen yield in the system
(Wimonsong and Nitisoravut 2015). Moreover, the effects of silver nanoparticles
concentration (0–200 nmol/L) on glucose-fed and pre-treated mixed bacteria culture
in an anaerobic batch reactor were investigated and revealed a 61.45% improvement
in fermentative hydrogen production at 20 nmol/L silver nanoparticles (Zhao et al.
2013). In another study, MCM41 nanoparticles with or without a functional group
influenced syngas fermentation in a system for biohydrogen production (Haiyang
et al. 2010). Findings from the aforementioned study showed that biohydrogen yield
was enhanced by a twofold in the present of 0.6 wt% of the MCM41 nanoparticles functionalized with 5% molar ratio of mercaptopropyl group (Haiyang et al.
2010). The enhanced hydrogen yield was due to improved CO-water mass transfer
(water–gas shift was biologically and effectively mediated) through the addition of
the functionalized MCM41 nanoparticles (Haiyang et al. 2010). Similarly, in a recent
study, Vi et al. (2017) optimized fermentative biohydrogen-producing conditions
of substrate concentration, pH and FeSO 4 nanoparticle concentration. Cumulative
biohydrogen yield of 3.50 g/L was achieved at optimized setpoints of 27.63 g/L,
6.10, and 0.063 g/L, for substrate concentration, pH, and FeSO 4 NP concentration,
respectively. Additional studies on the influence of different nanoparticles on biohydrogen production are summarized in Table 3 (Hydrogen yield: Highest H 2 yield in
mol H 2 /mol substrate, Nanoporous activated carbon: NAC, Nickel-graphene: Ni-C).
171
2014). These microorganisms are able to utilize organic matter such as lignocellulosic wastes, food wastes, municipal wastes, and animal manure during dark fermentation (Han et al. 2011). The application of nanoparticles for the improvement of
dark fermentative biohydrogen production has been reported in several studies as
shown in Table 3. Many of these efforts have yielded positive and desirable results.
A plausible explanation for increased biohydrogen yields is due to the ability of
nanoparticles to improve the process buffering capacity, which in turn stimulates and
enhances the activity of hydrogenase enzymes and substrate hydrolysis (Han et al.
2011). The addition of nanoparticles has shown to enhance the hydrogen-producing
metabolic pathways such as acetate and butyrate reactions, hydrolysis and acidification processes. For instance, the study by Han et al. (2011) supplemented haematite
nanoparticles at 200 mg/L as a bioactive to a bacterial mixed culture (pH 6.0, at
35 °C), and this resulted in a 30% improvement in the hydrogen yield (Table 3). The
authors attributed this increase to enhanced metabolic activities that favour hydrogen
formation pathways (Han et al. 2011).
Furthermore, Wimonsong and Nitisoravut (2015) investigated the activity of nanoporous activated carbon (NAC) in batch fermentative biohydrogen production (using
sucrose-fed anaerobic mixed bacteria culture, at 37 °C). The nanoporous activated
carbon resulted in low concentration of butyric acid with 77% absorption capacity,
thereby increasing the buffering capacity of the system (Wimonsong and Nitisoravut
2015). This invariably improves the physiological state and fermentative activities
of biohydrogen producing microbes that lead to high hydrogen yield in the system
(Wimonsong and Nitisoravut 2015). Moreover, the effects of silver nanoparticles
concentration (0–200 nmol/L) on glucose-fed and pre-treated mixed bacteria culture
in an anaerobic batch reactor were investigated and revealed a 61.45% improvement
in fermentative hydrogen production at 20 nmol/L silver nanoparticles (Zhao et al.
2013). In another study, MCM41 nanoparticles with or without a functional group
influenced syngas fermentation in a system for biohydrogen production (Haiyang
et al. 2010). Findings from the aforementioned study showed that biohydrogen yield
was enhanced by a twofold in the present of 0.6 wt% of the MCM41 nanoparticles functionalized with 5% molar ratio of mercaptopropyl group (Haiyang et al.
2010). The enhanced hydrogen yield was due to improved CO-water mass transfer
(water–gas shift was biologically and effectively mediated) through the addition of
the functionalized MCM41 nanoparticles (Haiyang et al. 2010). Similarly, in a recent
study, Vi et al. (2017) optimized fermentative biohydrogen-producing conditions
of substrate concentration, pH and FeSO 4 nanoparticle concentration. Cumulative
biohydrogen yield of 3.50 g/L was achieved at optimized setpoints of 27.63 g/L,
6.10, and 0.063 g/L, for substrate concentration, pH, and FeSO 4 NP concentration,
respectively. Additional studies on the influence of different nanoparticles on biohydrogen production are summarized in Table 3 (Hydrogen yield: Highest H 2 yield in
mol H 2 /mol substrate, Nanoporous activated carbon: NAC, Nickel-graphene: Ni-C).