Microbial production of electricity is an important form of bioenergy since Microbial Fuel cells (MFC) offer the possibility of extracting electric current from a wide range of organic wastes and renewable biomass. Factors affecting the MFC operational effectiveness are the MFC design and the bacterial metabolism and electron transfer. The purpose of this study is to identify species which are responsible for electricity generation so as to build a suitable consortium and to investigate the relative efficiencies between the microbial consortiums. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a MFC with synthetic media as a substrate increased the output from an initial level of 34 mA to a maximal level of 363 mA. Scanning electron microscope image indicated the enhanced microbial biofilm deposition over the electrode which were not initially detected in the community

Arti Yadav

Dimpal Parida

Muralidharan Ayyappan

Ramya Mohandass

English

Nature Precedings

CONSORTIUM BUILDING FOR PEM MFC USING  
SYNTHETIC MEDIA AS SUBSTRATE 
Dimpal Parida, Arti Yadav and A. Muralidharan*  
School of Bioengineering, SRM University, Chennai 603203, India 
muralifly@hotmail.com 
 
Abstract: Microbial production of electricity is an important form of bioenergy since Microbial Fuel cells 
(MFC) offer the possibility of extracting electric current from a wide range of organic wastes and renewable 
biomass. Factors affecting the MFC operational effectiveness are the MFC design and the bacterial metabolism 
and electron transfer. The purpose of this study is to identify species which are responsible for electricity 
generation so as to build a suitable consortium and to investigate the relative efficiencies between the microbial 
consortiums. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment 
of a MFC with synthetic media as a substrate increased the output from an initial level of 34 mA to a maximal 
level of 363 mA. Scanning electron microscope image indicated that the enhanced microbial biofilm deposition 
over the electrode which were not initially detected in the community.  
Keywords: microbial fuel cell; proton exchange membrane; microbial consortium; electricigens 
Introduction 
MFCs are bioelectrochemical systems which convert biomass into electricity through the metabolic activity of 
the microorganisms. Electrons produced by the bacteria from the substrate are transferred to the anode under 
anoxic conditions and flow to the cathode linked by a conductive material containing a resistor. The electron 
donor can be a reduced product of microbial metabolism that facilitates electron transfer by accepting electrons 
from the microbes and donating them to the anode. The cathode may be exposed to the air or submerged in 
aerobic water. Protons released from oxidation of the organic matter migrate to the cathode through a cation-
selective membrane that limits diffusion of oxygen into the anode chamber. Electrons, protons and oxygen 
combine at the cathode surface to form water. 
Current generation in microbial fuel cells (MFCs) is dependent on the presence of exoelectrogenic bacteria that 
oxidize organic matter and transfer electrons to the anode (Logan, 2008). Pure exoelectrogenic cultures have 
been tested as inoculums for MFCs, but the power densities generated were usually lower than those obtained 
using a mixed culture in the same MFC (Ishii et al., 2008), although some pure cultures produced power 
densities equal to or higher than those of the mixed culture (Nevin et al., 2008).   
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A microbial consortium is two or more microbial groups living symbiotically as one could find in activated 
sludge basins, biofilms found on various soil and aquatic ecosystems. Microbial consortia are efficient at 
degrading complex organic wastes than single strains of organisms. 
The term electricigen was coined to make a clear distinction in the mechanisms of power production in 
microbial fuel cells (Lovley, 2006). Electricigens are microorganisms that conserve energy to support growth by 
completely oxidizing organic compounds to carbon dioxide with direct electron transfer to the anodes of 
microbial fuel cells.  Electricity production with electricigens has a number of advantages which include high 
coulombic efficiency.  
In this study several sets of microbial consortium has been built which was then inoculated in synthetic media 
which produced varying current output. 
Materials and Methods 
The PEM MFC reactor set up consists of two 1000 ml (14 cm length) plastic container, one for anodic and the 
other one for cathodic chamber. Both the chambers are separated from each other by a cation exchange 
membrane (Nafion 117, Dupont & Co. USA). The PEM membrane was connected with the two chambers by 
union and blanches with a length of 7cm. Three carbon electrodes were used in each chamber. The anodic 
chamber contains synthetic media as well as the inoculated cultures which form the consortium. The cathodic 
chamber is filled with water. The transfer of electron takes place externally through circuit and internally 
through potential difference created by oxygen gradient. 
Synthetic media (Composition per litre) 
8800 mg NaCl, 3000 mg NaHCO3, 275 mg CaCl2, 1500 mg KH2PO4, 2200 mg K2HPO4, 10 mg FeSO4.7H2O, 
1.0 mg ZnCl2, 500 mg NH4Cl, 2.0 mg KCl, 0.1 mg H3BO3, 180 mg MgSO4.7H2O, 1mg EDTA, 450 mg 
(NH4)2SO4. To this medium, a carbon source (glucose 2000 mg) was added. The autoclaved media was filled in 
the anodic chamber of the MFC.  
Consortium Building 
Five sets of microbial consortium have been built for PEM MFC. The microbes were taken in different 
combination and used in synthetic media PEM MFC which showed relative efficiency of power output. All 
microorganisms were procured from MTCC, IMTECH, India. 
Set 1  
Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhii  and  
Staphylococcus aureus                               
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Set 2  
Pseudomonas aeruginosa, Alcaligenes faecalis, Enterococcus gallinarum, Aeromonas hydrophila, Escherichia 
coli and Enterococcus  faecalis 
Set 3  
Klebsiella pneumonia, Enterococcus faecalis, Enterococcus gallinarum, Staphylococcus aureus, Escherichia 
coli and Obligatory aerobe Bacillus subtilis 
Set 4 
Proteus vulgaris, Alcaligenes faecalis, Enterococcus gallinarum, Lactobacillus ferment, Lactobacillus 
plantarum and Aeromonas hydrophila                                                                                                               
Set 5 
Staphylococcus epidermis, Enterobacter aerogenes, Enterococcus  faecalis, Alcaligenes faecalis, Enterococcus 
gallinarum and Aeromonas hydrophila 
These sets of microbial cultures were taken and grown in LB/NB and incubated overnight in a shaker. The well 
grown cultures were inoculated in synthetic media of anodic chamber of PEM MFCs.                                                                       
SEM analysis using FEI Quanta 200 FEG 
Scanning electron microscopy was done to view the biofilm deposition over carbon electrode surface.  
Results and Discussions 
All MFCs were kept in room temperature of 37oC for a period of 30 days and the readings were recorded at the 
interval of 24h. 
 
Fig. 1:  Relative efficiencies between five sets of consortia 
Among all the consortia built, set 2 consortia showed maximum current output.  
 
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CFU for set 2 with different microbial load 
CFU were calculated for set 2 of 10-6 dilution for day 5 with varying microbial concentration of 1, 2 and 3 ml.  
Table 1:   Number of colonies at 10-6 dilution on day 5 for set 2 MFC 
                          MFC set up                    No of colonies 
                              Set 2(A)                        3.3 × 107 
                              Set 2 (B)                        5.6× 107 
                              Set 2 (C)                      16.5× 107 
 
Day 21 (275 mA)                              Day 21 (307 mA)                             Day 21 (363 mA) 
                         
Set 2 PEM MFC with 1 ml culture  Set 2 PEM MFC with 2 ml culture Set 2 PEM MFC with 3 ml culture 
 
Fig. 2: Comparative analysis of set 2 PEM MFC with varying microbial load. 
Fig. 3:  Relative efficiencies between MFC set 2 with different microbial concentrations. 
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Table 2: Consolidated readings  
                        MFC  Consortium  Set up Maximum current ( µA) 
                         Consortium 1                                                                   128 
                         Consortium 2 198 
                         Consortium 2(A) 275 
                         Consortium 2(B) 307 
                         Consortium 2(C) 363 
                         Consortium 3 079 
                         Consortium 4 152 
                         Consortium 5 134 
 
Fig. 4: Bar diagram representing maximum current output for each consortium 
 
SEM analysis 
Fig. 5: SEM image of plain anode                     Biofilm deposition over anode  
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Conclusion 
Under present investigation, enrichment by repeated transfer of a bacterial consortium harvested from the anode 
compartment of a MFC using synthetic media as a substrate increased the output from an initial level of 34 mA 
to a maximal level of 369 mA. This result was obtained with an average loading rate of 1g of glucose liter/day. 
MFCs operated using mixed cultures achieve greater power densities than those with pure cultures. Thus, 
different microbial consortiums give varying current output. There has been an increase in recent years in the 
number of reports of microorganisms that can generate electrical current in microbial fuel cells. Further studies 
would be necessary to optimize the electricity production from this synthetic media PEM MFC. Efforts should 
be made to maximize the transport of electrons from bacteria to the electrode surface by identifying efficient 
electricigens.  
References 
Logan BE (2008) Microbial Fuel Cells. John Wiley and Sons, Inc., Hoboken, New Jersey. p. 200. 
Ishii S, Watanabe K, Yabuki S, Logan BE, Sekiguchi Y (2008) Comparison of electrode reduction  activities of 
Geobacter sulfurreducens and an enriched consortium in an air-cathode microbial fuel cell Appl Environ 
Microbiol 74: 7348–7355. 
Nevin KP, Richter H, Covalla SF, Johnson JP, Woodard TL, Orloff AL, Jia H, Zhang M, Lovley DR (2008) 
Power output and Coulombic efficiencies from biofilms of Geobacter sulfurreducens comparable to mixed 
community microbial fuel cells Environ Microbiol 10: 2505–2514. 
Lovley DR (2006) Bug juice: harvesting electricity with microorganisms. Nature Rev Microbiol 4: 497–508. 
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Bug juice: harvesting electricity with microorganisms. Nature Rev Microbiol 4: 497–508. N a t u r e P r e c e d i n g s : h d l : / n p r e

Microbial Fuel Cells.

Power output and Coulombic efficiencies from biofilms of Geobacter sulfurreducens comparable to mixed community microbial fuel cells

Consortium Building For PEM MFC Using Synthetic Media As Substrate

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Consortium Building For PEM MFC Using Synthetic Media As Substrate

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