Part C | 20.4
522 Part C Marine Genomics
lack of material has inspired innovative chemistry that
develops new methodologies for the synthesis and modification of natural products [20.132–135]. Still, these
methodologies, realized at conventional macroscale,
are labor intensive, time consuming, and expensive. In
addition, scale-up from research to mass production remains troublesome because of the volume to surface
ratio that affects the thermal and mass transport properties of the reaction and requires readjustment in the
process at each stage of the scale-up.
Microreaction technology provides the means of
addressing those limitations. Single microfluidic devices can be used in a laboratory to reduce the cost,
time, and labor of the experiments. In addition, microfluidic technologies render easier scale-up of a reaction process from research to mass production, as
multiple devices can be used simultaneously. For example, a recent study reported the use of microfluidic systems for the synthesis of pristine [20.136]
(or 2,6,10,14-tetramethylpentadecane), a saturated isoprenoid isolated from the basking shark, Cetorhinus
maximus [20.139, 140]. The synthesis of pristane involves different steps, namely oxidation, alkylation, dehydratation, and hydrogenation. In this process, dehydration is the most challenging part. When the reaction
is performed at a gram scale, purity of the final product
does not exceed 20%, even with repeated distillation
or silica gel chromatography, which cannot be used
for kilogram-scale mass production. Using ten commercially available Comet X-01 micromixers arranged
in parallel (Fig. 20.8a), Tanaka et al. successfully performed an 8 kg-scale dehydration over 34 days in
one batch [20.136]. The solution eluted from the
micromixing system was then quenched, extracted,
and concentrated. The mixtures were quickly passed
through a short silica gel pad to remove hydrophilic byproducts. Finally, hydrogenation in the presence of 10%
Pd/C under hydrogen atmosphere provided pristane in
5055% overall yields ( 5 kg) with > 99% purity,
based on gas chromatographic analysis. In addition, the
synthetic pristane obtained with the microfluidic system
was confirmed to induce antibody production in mice
twice as efficiently as natural pristane or other synthetic
products, due to the non-negligible contamination of the
other hydrophobic compounds [20.136].
20.4.2 Marine Bacteria-Based Microrobot
Fabrication and Control
With the development of MEMS and robotics [20.141–
145], microrobotics has become the focus of attention
worldwide for its potential applications in medical diagnosis, targeted delivery, in vivo sensing, cell manipulation, and material removal in the human body [20.146–
149]. However, because of the size limitation, energy
supply is always one of the bottlenecks in the development of microrobots [20.145, 149–151]. Recently,
E. coli [20.152] and marine bacteria [20.137] have been
successfully integrated in the design of microrobots and
has been used as a propulsion system [20.151]. Obviously, the use of conventional cell culture system, such
as flasks or plates, is not the most suitable for studying the control of microrobot behavior, because of the
high surface ratio between the substrate and the bacteria. The ability to easily control biological conditions
and the dynamic fluidic environment within the system [20.150–155] makes microfluidics ideal tools for
microrobot-based studies. Quifeng et al. recently developed a microfluidic device to control and track marine
magnetotactic bacteria (MBT) ovoid MO-1 cell-based
microrobot (MBT-microrobot) [20.137]. The system is
shown in Fig. 20.7b. In this study, MO-1 bacteria were
used as a carrier system on which microbeads were attached. The control and tracking system consisted of
an inverted microscope tracking device, a set of electromagnetic coil devices embedded in the stage of the
inverted microscope brackets, and a microfluidic chip at
the center of the set of the electromagnetic coil device.
The microfluidic chip was made of PDMS and composed of a single channel with two pools, as shown in
Fig. 20.8b. The control and tracking device could manipulate the movement of the MTB-microrobots within
the microfluidic channels and trap the swimming cells
within the pools where circular magnetic fields were applied, showing the possibility to use the circular field as
a stop control system.
20.4.3 Seawater Desalination
The shortage of fresh water is one of the most important
challenges facing today’s world. Population growth, enhanced living standards, and the expansion of industrial
and agricultural activities have created unprecedented
demands on clean water supplies all over the world.
Nowadays, nearly half a billion people in 31 different countries, mainly in Africa and the Middle East,
suffer from water shortage. In 2025, this will grow to
four billion people in 48 countries [20.156, 157]. Converting seawater, which represents about 97% of the
total water resources on Earth, into freshwater may
provide the solution to the worldwide water-shortage
problem. However, current desalination methods, such
522 Part C Marine Genomics
lack of material has inspired innovative chemistry that
develops new methodologies for the synthesis and modification of natural products [20.132–135]. Still, these
methodologies, realized at conventional macroscale,
are labor intensive, time consuming, and expensive. In
addition, scale-up from research to mass production remains troublesome because of the volume to surface
ratio that affects the thermal and mass transport properties of the reaction and requires readjustment in the
process at each stage of the scale-up.
Microreaction technology provides the means of
addressing those limitations. Single microfluidic devices can be used in a laboratory to reduce the cost,
time, and labor of the experiments. In addition, microfluidic technologies render easier scale-up of a reaction process from research to mass production, as
multiple devices can be used simultaneously. For example, a recent study reported the use of microfluidic systems for the synthesis of pristine [20.136]
(or 2,6,10,14-tetramethylpentadecane), a saturated isoprenoid isolated from the basking shark, Cetorhinus
maximus [20.139, 140]. The synthesis of pristane involves different steps, namely oxidation, alkylation, dehydratation, and hydrogenation. In this process, dehydration is the most challenging part. When the reaction
is performed at a gram scale, purity of the final product
does not exceed 20%, even with repeated distillation
or silica gel chromatography, which cannot be used
for kilogram-scale mass production. Using ten commercially available Comet X-01 micromixers arranged
in parallel (Fig. 20.8a), Tanaka et al. successfully performed an 8 kg-scale dehydration over 34 days in
one batch [20.136]. The solution eluted from the
micromixing system was then quenched, extracted,
and concentrated. The mixtures were quickly passed
through a short silica gel pad to remove hydrophilic byproducts. Finally, hydrogenation in the presence of 10%
Pd/C under hydrogen atmosphere provided pristane in
5055% overall yields ( 5 kg) with > 99% purity,
based on gas chromatographic analysis. In addition, the
synthetic pristane obtained with the microfluidic system
was confirmed to induce antibody production in mice
twice as efficiently as natural pristane or other synthetic
products, due to the non-negligible contamination of the
other hydrophobic compounds [20.136].
20.4.2 Marine Bacteria-Based Microrobot
Fabrication and Control
With the development of MEMS and robotics [20.141–
145], microrobotics has become the focus of attention
worldwide for its potential applications in medical diagnosis, targeted delivery, in vivo sensing, cell manipulation, and material removal in the human body [20.146–
149]. However, because of the size limitation, energy
supply is always one of the bottlenecks in the development of microrobots [20.145, 149–151]. Recently,
E. coli [20.152] and marine bacteria [20.137] have been
successfully integrated in the design of microrobots and
has been used as a propulsion system [20.151]. Obviously, the use of conventional cell culture system, such
as flasks or plates, is not the most suitable for studying the control of microrobot behavior, because of the
high surface ratio between the substrate and the bacteria. The ability to easily control biological conditions
and the dynamic fluidic environment within the system [20.150–155] makes microfluidics ideal tools for
microrobot-based studies. Quifeng et al. recently developed a microfluidic device to control and track marine
magnetotactic bacteria (MBT) ovoid MO-1 cell-based
microrobot (MBT-microrobot) [20.137]. The system is
shown in Fig. 20.7b. In this study, MO-1 bacteria were
used as a carrier system on which microbeads were attached. The control and tracking system consisted of
an inverted microscope tracking device, a set of electromagnetic coil devices embedded in the stage of the
inverted microscope brackets, and a microfluidic chip at
the center of the set of the electromagnetic coil device.
The microfluidic chip was made of PDMS and composed of a single channel with two pools, as shown in
Fig. 20.8b. The control and tracking device could manipulate the movement of the MTB-microrobots within
the microfluidic channels and trap the swimming cells
within the pools where circular magnetic fields were applied, showing the possibility to use the circular field as
a stop control system.
20.4.3 Seawater Desalination
The shortage of fresh water is one of the most important
challenges facing today’s world. Population growth, enhanced living standards, and the expansion of industrial
and agricultural activities have created unprecedented
demands on clean water supplies all over the world.
Nowadays, nearly half a billion people in 31 different countries, mainly in Africa and the Middle East,
suffer from water shortage. In 2025, this will grow to
four billion people in 48 countries [20.156, 157]. Converting seawater, which represents about 97% of the
total water resources on Earth, into freshwater may
provide the solution to the worldwide water-shortage
problem. However, current desalination methods, such