1. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0
Available online at www.sciencedirect.com
journal homepage: www.elsevier.com/locate/he
A novel microbial fuel cell stack for continuous production
of clean energy
M. Rahimnejad a, A.A. Ghoreyshi a,*, G.D. Najafpour a, H. Younesi b, M. Shakeri c
a
Biotechnology Research Lab., Faculty of Chemical Engineering, Noshirvani University, Babol, Iran
b
Department of Environmental Science, Faculty of Natural Resources and Marine Science, Tarbiat Modares University, Noor, Iran
c
Faculty of Mechanical Engineering, Noshirvani University, Babol, Iran
article info abstract
Article history: Production of sustainable and clean energy through oxidation of biodegradable materials
Received 8 November 2011 was carried out in a novel stack of microbial fuel cells (MFCs). Saccharomyces cerevisiae as an
Received in revised form active biocatalyst was used for power generation. The novel stack of MFCs consist of four
25 December 2011 units was fabricated and operated in continuous mode. Pure glucose as substrate was used
Accepted 28 December 2011 with concentration of 30 g lÀ1 along with 200 mmol lÀ1 of natural red (NR) as a mediator in
Available online 28 January 2012 the anode and 400 mmol lÀ1 of potassium permanganate as oxidizing agent in the cathode.
Polarimetry technique was employed to analyze the single cell as well as stack electrical
Keywords: performance. Performance of the MFCs stack was evaluated with respect to amount of
Microbial fuel cell electricity generation. Maximum current and power generation in the stack of MFC were
Stack 6447 mA.mÀ2 and 2003 mW.mÀ2, respectively. Columbic efficiency of 22 percent was
Columbic efficiency achieved at parallel connection. At the end of process, image of the outer surface of
Electricity generation graphite electrode was taken by Atomic Force Microscope at magnification of 5000. The
Saccharomyces cerevisiae high electrical performance of MFCs was attributed to the uniform growth of microor-
ganism on the graphite surface which was confirmed by the obtained images.
Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights
reserved.
1. Introduction (BFCs) are a subset of fuel cells which employ active bio-
catalysts for production of bioelectricity instead of expensive
Consumption of fossil fuels has created serious threats for metal catalysts used in conventional fuel cells such as proton
human being, such as global warming and environment exchange membrane fuel cell (PEMFC). The main types of
pollution. In addition, proven reserves of fossil fuels are finite BFCs are defined by the biocatalyst used in anode compart-
and world may be faced with serious shortage of energy in ment. Microbial fuel cells (MFCs) employ living cells for
a near future. These crucial issues have encouraged oxidation of organic substrate, whereas enzymatic fuel cells
researchers to seek alternatives for conventional fossil fuels use active enzymes for the same purposes [5,6]. MFCs have
[1,2]. Fuel cells are known as renewable and environmental- been considered as new alternatives to conventional
friendly sources of energy [3]. Fuel cells are electrochemical batteries for electricity generation in power sources [7]. The
engines that convert directly the chemical energy existing in main advantage of MFCs is that they typically have long
the chemical bonds into electricity [4]. Biological fuel cells lifetimes (up to five years) [8,9]. MFCs are capable to oxidize
* Corresponding author. Tel.: þ98 111 323 4204; fax: þ98 111 321 0975.
E-mail address: aa_ghoreyshi@nit.ac.ir (A.A. Ghoreyshi).
0360-3199/$ e see front matter Copyright ª 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
doi:10.1016/j.ijhydene.2011.12.154

2. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0 5993
simple carbohydrates to carbon dioxide via biochemical The main objective of present research was to assemble
reactions [10]. a number of individual MFCs in a specially designed stack to
Recently, great attentions have been paid to MFCs due to enhance electrical output for practical applications. In this
their mild operating conditions and using variety of biode- research, a new design of MFCs stack composed of four
gradable substrates as fuel [11]. Traditional MFCs consist of anodes and three cathodes compartments were used .All
two separate compartments named as cathode and anode experiments were conducted in continuous mode at optimum
[12]. Some microorganisms such as Saccharomyces species and hydraulic residence time (HRT) as well as glucose concentra-
Escherichia coli are unable to transfer directly the produced tion determined based our pervious results [33,34]. The
electrons to anode surface [13,14]. Therefore, such bio- uniformity of electricity generation at each individual MFC
catalysts require electron shuttles in anode chamber of MFCs was investigated. The collective current and voltage produc-
[15]. The performance of MFCs mainly depend on several tion in series and parallel connections of MFCs was also
important factors, such as system architecture, electrode studied. Results of present research demonstrated that the
material, electrode surface area, bacterial species, types of novel fabricated stack was remarkably enhanced current and
organic matter, operating conditions (solution conductivity, power at optimum conditions which can be used for low
pH), and type of catholyte [14,16e20]. consumption electrical devices.
Single MFCs were used by many researchers for the
purpose of power generation by means of pure and mixed
cultures of active biocatalysts [21e23]. A series of attempts 2. Materials and methods
has been made to improve MFCs’ performance using suitable
substrates and microorganisms by application of process 2.1. Microorganism and cultivation
optimization [16,24e26]. Maximum power density of
10.2 mW.mÀ2 was obtained by Park and Zeikus using She- The system was inoculated with pure culture of Saccharomyces
wanella putrefacians and lactate as a substrate in an MFC [13]. cerevisiae PTCC 5269. The yeast was supplied by Iranian
Power generation by a pure culture of Geobacter metal- Research Organization for Science and Technology (Tehran,
lireducens in a dual chambered MFC was investigated. It was Iran). The microorganism was grown at anaerobic condition in
found that maximum power was about the same value ob- an anaerobic jar. The prepared medium for the seed culture
tained in a mixed culture originated from wastewater consisted of glucose, yeast extract, NH4Cl, NaH2PO4, MgSO4
(38 mW.mÀ2) [27]. Cheng and his coworkers have achieved and MnSO4: 10, 3, 0.2, 0.6, 0.2 and 0.05 g.lÀ1, respectively. The
maximum power of 462 mW.mÀ2 in a cubic MFC [28]. The medium was autoclaved at 121 C and 15 psig for 20 min.
obtained results from others researchers have demonstrated The medium pH was initially adjusted to 6.5 and the
that the produced power from single MFC was too low to be inoculums were introduced into the media at ambient
used even in low consumption devices. Therefore, a number temperature. The inoculated cultures were incubated at 30 C.
of single MFC has to be connected in parallel or series to The organism was fully grown in a 100 ml flask without any
provide enough power for a specific application such as agitation for the duration of 24 h.
a vehicle or an uninterruptible power supply. Any desired
voltage or current can be obtained by series or parallel 2.2. Stacked MFCs set up
connection of a few single cells. A combination of single MFC
connected in parallel and/or series is called a fuel cell stack The cubic stack of MFCs was fabricated from Plexiglas mate-
[28,29]. rial and used for power generation in laboratory scale. Stacked
Connecting several individual cells in series adds the MFCs was assembled from four individual anodes and three
voltages, while a unique current flows through all MFCs. cathodes compartments. Schematic diagram and photo image
When several single cells are connected in parallel, the voltage of the fabricated cells are shown in Fig. 1a and b, receptively.
averages and the currents are added [29]. Wilkinson has used The volume of each chamber (anodes and cathodes chambers)
six individual cells named ‘gastrobots’ for a digester of food was 460 ml with a working volume of 350 ml. The sample port
residues [30]. Also Aelterman and his research team have used was provided for each anode chamber with wire point input
six anode and cathode in their stack. They have reported the and inlet port. The selected electrodes for all separated cell
stack in series or in parallel had increased voltage and current, were unpolished graphite plates, size of 40 Â 60 Â 1.2 mm.
respectively [29]. Oh and Logan have reported that the oper- Proton exchange membrane (cross-sectional area: 32 cm2) was
ation of MFCs in series connection had the risk of voltage used to separate two compartments. Table 1 shows a list of
reversal [31]. The above discussion reveals that a stack of components and the materials used for fabrication of stacked
MFCs is required to obtain higher electrical outputs. MFCs. Proton exchange membrane, Nafion 117, was subjected
Liu et al. have conducted similar research in fed batch to a course of pretreatment to take off any impurities. For this
system. They have combined two single MFCs as stack. Their purpose, it was boiled for 1 h in 3 percent H2O2, washed with
system had significantly high power outputs; where the anode deionized water, 0.5 M H2SO4, and finally washed with
and cathode were sandwiched between two proton exchange deionized water. In order to maintain a good conductivity for
membranes [32]. The polarization curves obtained in their membrane, the anode and cathode compartments were filled
experiments were almost identical for all cells; as there was with deionized water when the microbial fuel cell was not
no mass transfer limitation in their anode chamber. However, in use. NR (200 mmol.lÀ1) and potassium permanganate
fed batch system may not be suitable for continuous power (400 mmol.lÀ1) supplied by Merck Company (Darmstadt,
generation. Germany) were used as mediator and oxidizing agent,

3. 5994 i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0
Fig. 1 e Fabricated cell (a) Schematic diagram (b) cell picture. Stacked MFC (c) Schematic diagram of the stacked assembly, (d)
Stacked picture with the auxiliary equipments.
respectively. The schematic diagram, photographic images prepared media in an up-flow mode using an adjustable
and auxiliary equipments of the fabricated stacked MFC peristaltic pump (THOMAS, Germany) and the oxygen needed
systems have been shown in Fig. 1c and d. In continuous at the cathode side was provided by an air sparger.
operation, all anode chambers were continuously fed with the
2.3. Chemical and analysis
Table 1 e Basic component was used for staked MFC. All chemicals and reagents used for the experiments were
Item Materials Company analytical grades and supplied by Merck (Darmstadt, Ger-
many). The pH meter, HANA 211 (Romania) model glass-
Anode electrodes Graphite plate ENTEGRIS, INC.
FCBLK-508305-00004, USA electrode was employed to measure pH values of the
Cathode electrodes Graphite plate ENTEGRIS, INC. aqueous phase. The initial pH of the working solution was
FCBLK-508305-00004, USA adjusted by addition of diluted HNO3 or 0.1 M NaOH solutions.
Anode Chambers Plexiglas Neonperse, Iran The surface images of the graphite plate electrodes before and
Cathode chambers Plexiglas Neonperse, Iran after each experimental run were obtained by Atomic Force
Proton exchange Nafion 117 SigmaeAldrich, USA
Microscope (AFM) at magnifications of 5000 (Easyscan2 Flex
Membranes
AFM, Swiss). The sample specimen size was 1 cm  1 cm for
Connection the cells Copper wire Khazar Electric, Iran
AFM analysis. AFM images were used to demonstrate the

4. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0 5995
physical characteristics of the electrode surface and to
examine the growth of yeast on the anode surface.
Dinitrosalicylic acid [3, 5(NO2)2C6H2e2OHeCOONa.H2O]
(DNS) method was employed to detect and measure substrate
consumption using colorimetric method [35]. Before analysis,
liquid samples were filtered by a 0.45 mm syringe membrane
(Sartorius Minisart).
Polarimetry technique was adapted to analyze the cell
electrical performance. Polarization curves were obtained
using an adjustable external resistance. Power and current
were calculated based on following equations:
P ¼ IÃ E (1)
I ¼ ðE=Rext Þ (2)
where P is generated power and E measured cell voltage; Rext
Fig. 2 e Open circuit voltage produced in a first individual
denotes external resistance and I indicates produced current.
MFC (cells 1 and 2) using S. cerevisiae as the active
The online recorded current and power were normalized by the
biocatalyst and 200 mmol.lL1 NR as mediators in anode
surface area of the used membrane. Analog digital data
chamber and 200 mmol.lL1 potassium permanganate in
acquisition was fabricated to record data point in every 4 min.
cathode chamber.
Measurements were carried out at variable resistances
imposed to the MFC. The current in the MFC was automatically
calculated and recorded dividing the obtained voltage by the
resistance in data logger. When the MFC was operated in
specified resistance. Then, the system provides power calcu-
continuous mode, the concentration of glucose in the feed
lation by multiplication of voltage and current. The provisions
tank solution was kept constant (30 g.lÀ1). HRT was fixed at
were provided for online observation of polarization curve
6.7 h by means of peristaltic pump in each anode chamber.
showing the variation of power density and MFC voltage with
The HRT was measured from the volume of medium and the
respect to current. The online system had the ability to operate
input flow rate to the anode compartment.
automatically or manually. While it operates in auto-mode, the
assembled relays were able to regulate automatically the
resistances. Voltage of MFC was amplified and then data were
transmitted to a microcontroller by an accurate analog to 3. Results and discussion
digital converter. The microcontroller was also able to send the
primary data to a computer by serial connection. In addition, Batch mode of operation is necessary to determine the best
a special function of MATLAB software (7.4, 2007a, Math Works, operating conditions to achieve maximum electrical output.
US) was used to store and display synchronically the obtained The optimum conditions for power generation in a single cell
data. The power, current and voltage were automatically MFC was found in our recent research [35]. To test the
recorded by the computer connected to the system. reproducibility of the results, batch mode of operation was
Columbic efficiency (CE) was calculated by division of total replicated at the predetermined condition. After inoculation
coulombs obtained from the cell by theoretical amount of
1000 300
coulombs that can be produced from glucose (Eq. (3)): Voltage
À Á Power
250
CE ¼ Cp =CT Â 100 (3) 800
Voltage (mV)
Power (mW.m-2)
Total coulombs are obtained by integrating the current 200
variation over time (Cp), where CT is the theoretical amount of 600
coulombs that can be produced from carbon source. For 150
continuous flow through the system, CE can be calculated on 400
the basis of generated current at steady state conditions as 100
follows [23]: 200
50
CE ¼ MI=FbqDS (4)
0 0
0 200 400 600 800 1000
In Eq. (4), F is Faraday’s constant; b is the number of moles of
Current (mA.m-2)
electrons produced per mole of substrate (24 mol of electrons
were produced in glucose oxidation in anaerobic anode Fig. 3 e Results of batch operated MFC with 30 g.lL1 glucose
chamber); S is the substrate concentration; q is flow rate of as the substrate. power density and voltage as function of
substrate and M is the molecular weight of used substrate current density in a cubic MFC (cell 1 and 2) using S.
(M ¼ 180.155 g.molÀ1) [36,37]. cerevisiae as the active biocatalyst, 200 mmol.lL1 NR as
In batch mode of operation, polarization curves were ob- mediators and 400 mmol.lL1 potassium permanganate as
tained at steady state condition while setting an adjustable oxidizing agent.

5. 5996 i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0
1200 600 oxidizer in anode and cathode, respectively. The initial volt-
Voltage ages for all individual cells were nearby 330 mV, which
current
1000 500 confirmed the reproducibility of electrical output with respect
to our previous experiments. Continuous generation of elec-
Power (mW.m-2)
Voltage (mV)
800 400 trons and protons along with substrate consumption by the
biocatalyst, led to enhancement of bioelectricity production.
600 300
The time required to reach steady state is quiet different for
systems using various substrates, concentration and micro-
400 200
organism. Fig. 2 depicts MFC performance in terms of OCV
improvement with respect to time. The cell voltage gradually
200 100
increased and reached to 847 mV after 38 h. The data were
0 0
recorded for duration of 75 h of operation.
0 500 1000 1500 2000 2500 The fabricated stack was operated in batch mode at room
Current (mA.m-2) temperature (25 Æ 1 C). Then, performance of the microbial
fuel cell was evaluated by the polarization curve. Once all
Fig. 4 e Results of continuous operated MFC with 30 g.lL1
individual cells have stabilized at maximum steady voltage,
glucose as the substrate. power density and voltage as
the polarization curves were obtained using an adjustable
function of current density in a cubic MFC (cells 1 and 2)
external resistance to determine variation of voltage with
using S. cerevisiae as the active biocatalyst, 200 mmol.lL1 NR
respect to current density. Fig. 3 demonstrates polarization
as mediators, 400 mmol.lL1 potassium permanganate as
curve for the first MFC (between chambers 1 and 2). The
oxidizing agent and 6.7 h HRT.
maximum generated power and current density were
241 mW.mÀ2 and 930 mA.mÀ2, respectively. Similar results for
other cells in stack were recorded; the obtained data are
of 30 g lÀ1 glucose in anode chamber with S. cerevisiae, data summarized in Table 1.
logger was set to record open circuit voltage (OCV) until Once stable voltage was established in each cell, the
steady state condition. An infinite resistance was used to batch operation was switched to continuous mode. In
obtain OCV in batch mode in presence of 200 mmol lÀ1 of NR continuous operation, the prepared substrate was injected
and 400 mmol lÀ1 of potassium permanganate as mediator and from the feed tank to anode compartment with a defined
1400 600 1200 600
Voltage Voltage
1200 current current
500 1000 500
Power (mW.m-2)
1000
Power (mW.m-2)
400
Voltage (mV)
800 400
Voltage (mV)
800
300 600 300
600
200 400 200
400
200 100 200 100
0 0 0 0
0 500 1000 1500 2000 2500 0 500 1000 1500 2000 2500
Current (mA.m-2) Current (mA.m-2)
Chamber 3 and 4 Chamber 2 and 3
1200 500 1200 600
Voltage Voltage
current current
1000 1000 500
400
Power (mW.m-2)
Power (mW.m -2)
Voltage (mV)
800 800 400
Voltage (mV)
300
600 600 300
200
400 400 200
100
200 200 100
0 0 0 0
0 500 1000 1500 2000 2500 3000 0 500 1000 1500 2000 2500 3000
Current (mA.m-2) Current (mA.m-2)
Chamber 6 and 7 Chamber 4 and 5
Fig. 5 e Results of continuous operated MFC with 30 g.lL1 glucose as the substrate. Power density and voltage as function of
current density in different individual cells. Experiment condition was similar to Fig. 4.

6. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0 5997
performance of MFCs stack with parallel connection was also
Table 2 e Optimum condition obtained from each
individual cell without feeding. investigated by polarization curve. Fig. 6 depicts variation
of voltage and power density as function of current density
Single cell Pmax Imax in Pmax OCV at S.S. condition
(polarization curve). The maximum current and power
number (mW.mÀ2) (mA.mÀ2) (mV)
density for parallel connection were 2003 mW.mÀ2 and
1e2 241 630 847 6447 mA.mÀ2, respectively. MFCs stack operated continuously
2e3 246 645 850
for duration of 3 days and polarization data indicated that the
3e4 243 639 849
power generation was stable.
4e5 244 641 849
5e6 244 644 851 OCV represents the highest voltage which is obtained in an
6e7 235 621 841 MFC. In an actual condition, there is a resistance in external
circuit. In order to obtain close circuit voltage, a 1 KU resis-
tance was fixed in external circuit and the system worked
flow rate (HRT of 6 h). Substrate with initial glucose at this situation for the period of 148 h. Fig. 7 shows the close
concentration of 30 g.lÀ1 and the same mediator and oxidizer circuit voltage and generated power was stable like open
concentration were continuously transferred through circuit voltage for the entire period of operation. Table 3
uniform flow distributors by means of peristaltic pump. compares results obtained for stacked MFCs in this work
Effect of HRT on performance of continuous MFC was with the similar works reported in literature for different
investigated in our previous research [33]. Polarization data substrates and microorganisms.
were obtained when the stable voltage output was estab- Based on obtained data, columbic efficiency (CE) for the
lished in continuous mode (after 3 days). Polarization curve parallel and series connections were 22 and 6.5 percent. Low
for the first MFC is shown in Fig. 4. The maximum generated CE may be due to the breakdown of sugars by the microor-
current and power density were 2100 mA.mÀ2 and ganism resulted in production of some intermediate prod-
490 mW.mÀ2, respectively. ucts that may play a significant role in decrease of CE
Polarization curves for other individual MFCs were plotted [38,39]. Aelterman et al. have achieved CE of 12.4 and 77.8
in Fig. 5. The polarization curves obtained for different single percent in series and parallel connections, receptively. They
MFCs indicated that the maximum current density and power have used 6 units of MFC in their stack; acetate as substrate
density for all individual cells were almost similar. However, and ulterex as the proton exchange membrane [29]. Differ-
the generated power and current in the last cell (cell 6 and 7) ences in CE of the parallel and series connected stacks were
was slightly less than the others. This may be attributed to reported [29]. Since both types of stacks operated at the
insufficient flow distribution inside the last cell (also see the same HRT; the difference in CE values was caused by the
reported values of power density in Table 2). higher current generated in parallel connection compared to
Combining appropriate number of single fuel cells may that of series connection. Thus, connection of MFCs in
provide adequate power source. In present work, four anodes series to form a stack of MFCs may not allow high current
and three cathodes chambers were connected to each other to densities [29]. The obtained results from the stacked MFCs
make a stack of MFCs. All anodes, except the first and last also proved its potential for scale up to achieve higher
anode (cells 1 and 7), were connected with two cathodes. To electrical outputs.
enhance voltage or current, all individual cells were con- AFM technique has been widely applied to provide elec-
nected in series and parallel, respectively. These special trode surface and morphological information. The outer
configurations led to OCV of 3230 and 1005 mV for series surfaces of the anode electrode before and after experiments
connection and the parallel connection, respectively. The were examined with AFM. Fig. 8 depicts the AFM images of the
shape and surface characteristic of the anode electrode
1200 2500
Voltage
1000 current
2000
Power (mW.m-2)
Voltage (mV)
800
1500
600
1000
400
500
200
0 0
0 2000 4000 6000 8000 10000
Current (mA.m-2)
Fig. 6 e Results of parallel staked MFC with initial 30 g.lL1
glucose as the substrate. Power density and voltage as Fig. 7 e Close circuit voltage and produced power from
function of current density in different individual cells. staked MFC at parallel mode with 1 KU resistances in
Other experimental conditions were similar to Fig. 4. external circuit for 148 h.

7. 5998 i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0
Table 3 e Production of bioelectricity in stacked MFC with different configuration were used.
Substrate Type Number Number Maximum Microorganisms Reference
of anode of cathode produced power
Sodium acetate H-type 2 2 460 mw.mÀ2 Mixed culture [31]
Glucose Cubic 2 2 256 mW Mixed culture [32]
Sodium acetate Cubic 6 6 258 W.mÀ3 Mixed culture [29]
Acetate Glucose H-type 2 2 460 mW.mÀ2 Mixed culture [31]
Brewery wastewater Tubular 2 2 1.2 W.mÀ3 Mixed culture [40]
Glucose Cubic 4 3 2003 mW.mÀ2 Pure culture This work
Fig. 8 e AFM images from outer surface of anode electrode before (a) and after (b) using in anode compartment.

8. i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0 5999
(graphite). A small piece of electrode (1 Â 1cm) before use in [2] Strik D, Terlouw H, Hamelers H, Buisman C. Renewable
anode chamber was analyzed by AFM. Two and three- sustainable biocatalyzed electricity production in
dimensional images of the graphite anode surface before a photosynthetic algal microbial fuel cell (PAMFC). Appl
Microbiol Biotechnol 2008;81:659e68.
and after use with magnification 5000 are shown in Fig. 8a and
[3] Wen Q, Wu Y, Cao D, Zhao L, Sun Q. Electricity generation
b. The obtained image demonstrated the microorganisms and modeling of microbial fuel cell from continuous beer
have well grown and formed uniform biofilm on all anode brewery wastewater. Bioresource Technol 2009;100:4171e5.
surfaces. This factor justifies the uniform electrical perfor- [4] Steele BCH, Heinzel A. Materials for fuel-cell technologies.
mance of all units. Nature 2001;414:345e52.
The main objective of present research was to achieve [5] Minteer SD, Liaw BY, Cooney MJ. Enzyme-based biofuel cells.
a suitable current and power for the application in small Curr Opin Biotechnol 2007;18:228e34.
[6] Rahimnejad M, Mokhtarian N, Najafpour G, Daud W,
electrical devices. As a demonstration, ten LED lumps and one
Ghoreyshi A. Low voltage power generation in a biofuel cell
digital clock used the fabricated stacked MFC as power source using anaerobic cultures. World Appl Sci J 2009;6:1585e8.
and both devices were successfully operated for the duration [7] Lyon DY, Buret F, Vogel TM, Monier JM. Is resistance futile?
of 2 days. changing external resistance does not improve microbial fuel
cell performance. Bioelectrochem 2010;78:2e7.
[8] Moon H, Chang I, Kim B. Continuous electricity production
4. Conclusion from artificial wastewater using a mediator-less microbial
fuel cell. Bioresour Technol 2006;97:621e7.
[9] Kim B, Chang I, Cheol Gil G, Park HS, Kim HJ. Novel BOD
A new stack of MFCs was designed, fabricated and operated
(biological oxygen demand) sensor using mediator-less
successfully in continuous mode of operation to enhance the microbial fuel cell. Biotechnol Lett 2003;25:541e5.
power generation. The system used pure glucose as substrate [10] Bond DR, Lovley D. Evidence for involvement of an electron
at concentration of 30 g lÀ1 and S. cerevisiae, as biocatalyst. shuttle in electricity generation by Geothrix fermentans.
Potassium permanganate was used as oxidizing agent in Appl Environ Microbiol 2005;71:2186.
cathode chamber to enhance the voltage. NR as electron [11] Picioreanu C, Katuri K, Van Loosdrecht M, Head I, Scott K.
Modelling microbial fuel cells with suspended cells and
mediator with low concentration (200 mmol.lÀ1) was selected
added electron transfer mediator. J Appl Electrochem 2010;
as electron mediator in anode side. The produced current and
40:151e62.
power by a single MFC was not sufficient for practical appli- [12] Rahimnejad M, Jafari T, Haghparast F, Najafpour GD,
cations even for use in low consumption electrical devices. Ghoreyshi AA. Nafion as a nanoproton conductor in
Therefore, the electrical outputs were enhanced using a novel microbial fuel cells. Turkish J Eng Env Sci 2010;34:289e92.
combination of four single MFCs in series and parallel [13] Park DH, Zeikus J. Electricity generation in microbial fuel
connection as a stacked MFCs. The obtained results from cells using neutral red as an electronophore. Appl Environ
Microbiol 2000;66:1292.
present study demonstrated that MFCs with anodes and
[14] Najafpour G, Rahimnejad M, Mokhtarian N, Daud W,
cathodes sandwiched between two proton exchange Ghoreyshi A. Bioconversion of whey to electrical energy in
membranes can be used as stack of MFCs. The maximum a biofuel cell using Saccharomyces cerevisiae. World Appl Sci J
voltage was 3230 mV for the series connection, with initial 2010;8:1e5.
glucose concentration of 30 g.lÀ1. Since, most of small elec- [15] Gil G, Chang I, Kim B, Kim M, Jang J, Park H, et al. Operational
trical devices required high currents rather than high voltage; parameters affecting the performance of a mediator-less
microbial fuel cell. Biosens Bioelectron 2003;18:327e34.
therefore parallel connections are preferred in this regard. The
[16] Logan BE, Regan JM. Microbial fuel cells-challenges and
maximum received power and current density based on peak
applications. Environ Sci Technol 2006;40:5172e80.
point in polarization curve were 2003 mW.mÀ2 and [17] He Z, Angenent L. Application of bacterial biocathodes in
6447 mA.mÀ2, respectively. The results indicated almost microbial fuel cells. Electroanalysis 2006;18:2009e15.
similar electrical performances for all individual cells which [18] Feng Y, Yang Q, Wang X, Logan B. Treatment of carbon fiber
showed a uniform power generation in the system. The result brush anodes for improving power generation in air-cathode
of study also demonstrated that the scale up of the system is microbial fuel cells. J Power Sources 1841-1844;195.
[19] Liu Z, Liu J, Zhang S, Su Z. Study of operational performance
possible by the use of more number of single MFC in stack.
and electrical response on mediator-less microbial fuel cells
fed with carbon-and protein-rich substrates. Biochem Eng J
2009;45:185e91.
Acknowledgments [20] Liu H, Logan B. Electricity generation using an air-cathode
single chamber microbial fuel cell in the presence and
absence of a proton exchange membrane. Environ Sci
The authors wish to acknowledge Biotechnology Research
Technol 2004;38:4040e6.
Center, Noshirvani University of Technology (Babol, Iran) for [21] Rabaey K, Lissens G, Siciliano S, Verstraete W. A microbial
the facilities provided to accomplish the present research. fuel cell capable of converting glucose to electricity at high
rate and efficiency. Biotechnol Lett 2003;25:1531e5.
[22] Chung K, Okabe S. Continuous power generation and
references microbial community structure of the anode biofilms in
a three-stage microbial fuel cell system. Appl Microbiol
Biotechnol 2009;83:965e77.
[1] Lovley D. Microbial fuel cells: novel microbial physiologies [23] Logan B, Hamelers B, Rozendal R, SchroDer U, Keller J,
¨
and engineering approaches. Curr Opin Biotechnol 2006;17: Freguia S, et al. Microbial fuel cells: methodology and
327e32. technology. Environ Sci Technol 2006;40:5181e92.

9. 6000 i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y 3 7 ( 2 0 1 2 ) 5 9 9 2 e6 0 0 0
[24] Rezaei F, Richard T, Brennan RA, Logan B. Substrate- extra cation exchange membrane. Biotechnol Letters 2008;
enhanced microbial fuel cells for improved remote power 30:1017e23.
generation from sediment-based systems. Environ Sci [33] Rahimnejad M, Ghoreyshi A, Najafpour G, Jafary T. Power
Technol 2007;41:4053e8. generation from organic substrate in batch and continuous
[25] Logan B. Microbial fuel cells. LibreDigital; 2008. flow microbial fuel cell operations. Appl Energy 2011;88:
[26] Kim N, Choi Y, Jung S, Kim S. Effect of initial carbon sources 3999e4004.
on the performance of microbial fuel cells containing Proteus [34] Najafpour G, Rahimnejad M, Ghoreyshi A. Enhancement of
vulgaris. Biotechnol Bioeng 2000;70:109e14. microbial fuel cell for electrical 1 output using mediators and
[27] Min B, Cheng S, Logan B. Electricity generation using oxidizing agents. Energy Sources Part A 2011;33:2239e48.
membrane and salt bridge microbial fuel cells. Water Res [35] Thomas L, Chamberlin G. Colorimetric chemical analytical
2005;39:1675e86. methods. Salisbury, England: The Tintometer Ltd; 1980.
[28] Cheng S, Liu H, Logan B. Increased power generation in 85e87.
a continuous flow MFC with advective flow through the [36] Oh S, Logan B. Proton exchange membrane and electrode
porous anode and reduced electrode spacing. Environ Sci surface areas as factors that affect power generation in
Technol 2006;40:2426e32. microbial fuel cells. Appl Microbiol Biotechnol 2006;70:162e9.
[29] Aelterman P, Rabaey K, Hai P, Boon N, Verstraete W. [37] Allen R, Bennetto H. Microbial fuel-cells. Appl Biochem
Continuous electricity generation at high voltages and Biotechnol 1993;39:27e40.
currents using stacked microbial fuel cells. Environ Sci [38] Huang L, Logan B. Electricity production from xylose in fed-
Technol 2006;40:3388e94. batch and continuous-flow microbial fuel cells. Appl
[30] Wilkinson S. “Gastrobots”dbenefits and challenges of Microbiol Biotechnol 2008;80:655e64.
microbial fuel cells in FoodPowered robot applications. [39] Huang L, Logan B. Electricity generation and treatment of
Autonomous Robots 2000;9:99e111. paper recycling wastewater using a microbial fuel cell. Appl
[31] Oh S, Logan B. Voltage reversal during microbial fuel cell Microbiol Biotechnol 2008;80:349e55.
stack operation. J Power Sources 2007;167:11e7. [40] Zhuang L, Zhou S. Substrate cross-conduction effect on the
[32] Liu Z, Liu J, Zhang S, Su Z. A novel configuration of performance of serially connected microbial fuel cell stack.
microbial fuel cell stack bridged internally through an Electrochem Commun 2009;11:937e40.