Biomedical Engineering Reference
In-Depth Information
Notwithstanding all these potential applications, low power output remains the
most challenging obstacle to their practical use. The involvement of a capacitor in
an MFC power system is considered a possible solution, enabling continuous
energy storing while being intermittently discharged at higher voltage. This raises
the need for development and cooperation in disciplines such as biology and
materials.
3.2.2 MFC Biosensors
The impacts of the ambient environment (such as organic types and content,
toxicants, pH, and temperature) on the activities of microorganisms can be
reflected by their metabolism and proliferation in MFCs, which would ultimately
alter the current generation. Therefore, an MFC can offer valuable real-time
information on the rate and nature of biodegradation process, and has been
proposed to work as a sensitive biosensor for environmental and bioprocess
monitoring [
107
]. It possesses several potential advantages over conventional
biosensors, such as high sensitivity and accuracy, applicability for remote or
dangerous sites, and self-sustained operation. Chang et al. [
108
] invented an MFC
sensor in which the current signal generated by the MFC was amplified to sen-
sitively reflect the biochemical oxygen demand in a continuous mode. An MFC
biosensor for in-situ assessment of microbial activity was also recently explored
[
109
]. In addition to monitoring, it should be noted that the capability of bacteria
to donate electrons to an external circuit with a controllable resistance may ulti-
mately make the MFC process amenable to real-time control. These are relatively
new but highly promising areas of MFC application for which research interest is
also rising in China, although relevant reports are still scarce to date.
3.2.3 Driving Synthesis Processes
How to utilize in situ the limited electrical power generated from MFCs is an
important issue for MFC development. Aside from their potential use as power
sources for low-power devices and biosensors, several studies have demonstrated
that it is also possible to use this energy to drive other bioprocesses. One such
bioprocess could be microbial electrosynthesis: the synthesis process catalyzed by
active microorganisms in microbial electrochemical cells, which is capable of
producing a variety of useful chemical compounds such as hydrogen, ethanol,
methane, and H
2
O
2
in a cost-effective way [
110
]. Usually, a small amount of
energy is needed to drive the thermodynamically unfavorable reactions, which
necessitates an external power supply. One way to address this is utilizing
bioelectricity from MFCs. Sun et al. [
4
] designed a microbial electrolysis
cell (MEC)-MFC coupled system, in which an MFC was used as an assistant
power source to drive H
2
production in an MEC. Without any external power
supply, considerable hydrogen production was achieved in this coupled system.
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