NewBioWorld A Journal of Alumni Association of Biotechnology (2019) 1(1):9-12
RESEARCH ARTICLE
Production of Bioelectricity using Microbial Fuel Cells
Fed with Synthetically Designed Wastewater
Reena Meshram and Shailesh Kumar Jadhav*
S.o.S. in Biotechnology, Pt.
Ravishankar Shukla University, Raipur (C.G.) 492010, India.
*Email- jadhav9862@gmail.com- +917712262583
ARTICLE
INFORMATION
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ABSTRACT
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Article history:
Received
18 August 2017
Received in revised form
2 August 2018
Accepted
4 November 2018
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Microbial fuel cells
(MFCs) are the electrochemical systems that harness electron from the
reduction of organic compounds using microbes as a catalyst. 3 combinations
from 4 electrodes that are, Zn (14.9cm×4.9cm), Carbon (14cm×1.5cm), Cu
(14.9cm×4.9cm) and Al (14cm×4.5cm) were assessed . Zn-C, as an anode-cathode
combination produced maximum voltage of 1.1±0.03V and current 1.5±0.12mA. In
present study,gram negative non-fermentative staphylococcus bacterium was
isolated from a mediator-less microbial fuel cell, fed with rice bran oil
refinery wastewater operated in fed-batch manner. The isolate produced
potential of 1.01±0.01V and current of 1.24±0.03mA using synthetic
wastewater. The newly isolated bacterium has potential of generating
electricity in MFC system and may hold many possibilities with different
wastewater as well as in practical applications.
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Keywords:
Membrane-less MFC
Wastewater
Electrogenic
Non-fermentative
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Introduction
The demand
for energy is surging and the major source for energy is fossil fuel. All the
non-renewable resources including fossil fuel are limited and pose negative
effect on environment. Concerns about these raise in demand and environmental
issues, intense search for renewable, sustainable and green alternatives to
fossil fuel are growing (Logan 2004). Bio
energy, derived from renewable resources provide novel alternatives to these nature depletive resources such as bio
fuel (ethanol and biodiesel)and bio power (pyrolysis and fuel cells) etc. one of the most
efficient approaches is Microbial fuel cell (MFC). MFC are the electrochemical
systems that use biocatalysts (microorganisms) for the conversion of chemical
energy of organic matter to electrical energy under much wider environmental
conditions (Allen and Bennetto 1993; Logan 2004).MFC converts chemical energy
directly into electricity with variety of substrates, thus is more efficient.
A typical
MFC consists of conventional electrochemical system i.e. anode and cathode
electrode provided with anaerobic anode and open air cathode. Electrons move to
the cathode compartment through the external circuit, and protons migrate
through a proton exchange membrane (PEM) or agar salt bridge (Min and Logan
2004; Logan et al. 2006). In
cathode compartment, protons get combined with oxygen to oxidize into water.
Since the electrons are generated by microbial metabolism, the microbes are of
primary importance. Thus, many studies till the date have been made to search
for an efficient microorganism like Shewanella
putrefaciens (Kim et al. 1999), Geobacter
sulfurreducens (Bond and Lovley 2003), Rhodoferax ferrireducens (Chaudhuri
and Lovley 2003) and Klebsiella pneumoniae (Zhang
et al. 2009).
Rapid industrialization
leads to generation of ample amount of wastes, which contaminates the receiving
water bodies. The world is facing crucial challenges of its handling, treatment
and disposal. The MFC technology offers advantages over the conventional
wastewater treatment approaches while generating electricity. It also reduces
the amount of sludge and cost of wastewater treatment (Ahn and Logan 2010). The
literature shows that in MFCs, various wastewaters have been treated such as
sewage (Liu et al. 2004; Ahn
and Logan 2010), swine wastewater (Kim et
al. 2008), effluent from paper and pulp industry (Huang and Logan 2008),
brewery wastewater (Feng et al. 2008),
effluent from sugar industry (Abhilasha and Sharma 2009), phenolic wastewater
(Luoa et al. 2009), rice mill wastewater
(Beheraet al. 2010) and distillery
(Mohanakrishna et al. 2010). The
present work aims to study isolation of bacterial strain from rice bran oil
refinery wastewater and the feasibility of bioelectricity generation by the
bacteria using it along with different combination of electrodes in
mediator-less double chambered MFC.
Materials and methods
Sample collection
Wastewater from a local oil
refinery, Shree Sita Refiners Pvt. Ltd. Arasnara, Durg, Chhattisgarh (India) has been
used for the isolation studies. The wastewater was collected in 5 L sterile
airtight plastic containers and was stored at 4±10C for short term. Designed synthetic wastewater was used to
check the potential of isolated bacterial strain.
Construction of Microbial Fuel Cell
Dual-chambered H-shape MFC was
fabricated with non-reactive, microwave proof polyvinyl chloride containers
with a working volume of 750 mL. It comprises of an anode and an open air-cathode
chambers. These chambers were kept intact with the aid of adhesive material
that is M-Seal and a UPVC pipe of dimension 6.1cm × 1.3 cm was used to physically
separate them. The pipes contained agar salt bridge (sodium chloride, 10% and
agar, 5%) which acts as a proton exchange material (Momoh and Naeyor 2010; Kumar et al. 2012) (Fig. 1).The MFC
were sterilized with saturated ethanol followed by heat sterilization at 850C
for 2hr and irradiated with UV for 30 min (Kuashik and Jadhav 2017) and was
operated under anaerobic microenvironment.
Figure 1: Schematic diagram of typical two chambered
MFC
Three combinations from four
electrodes viz C (14cm×1.5cm), Zn
(14.9cm×4.9cm), Cu (14.9cm×4.9cm) and Al (14cm×4.5cm) (B. R. Instrument and equipments,
Chhattisgarh, India) were checked assuming that larger surface area of
electrode may provide larger area for biofilm formation and good electron
transfer (Prabowo et al. 2016). External copper wires along with alligator
clips were used to connect the electrodes to the digital multimeter (KUSAM-MECO
603) (Logan 2005). The anode compartments were subjected to a leak proof
sealing of joints and the exposed metal surfaces sealed with a nonconductive
epoxy to avoid corrosion (Kumar et al.
2012). The open air-cathodechamber was filled with 50mM phosphate buffer
(pH 7). In present study, oxygen was employed as the final electron acceptor
(Feng et al. 2008).
MFC Operation
The MFC setup was run in
fed-batch mode. The performance of all the MFCs was evaluated by measuring open
circuit voltage (OCV) and current. Constant voltage output was considered as
indicator of stable performance of MFC. For the isolation and electrode
optimization study, anodic chamber was filled with 750 ml of collected wastewater
sample and cathode chamber was filled with phosphate buffer. For screening of
electrogenic property of isolated bacterial strain, synthetically designed
wastewater (glucose 3.0g/l, FeCl3 25×10-3g/l, NH4Cl 0.5g/l, CaCl2 5.0×10-3g/l, K2HPO4 0.25 g/l, KH2PO4 0.25g/l, MgCl2 0.3g/l, NiSO4 16.0×10-3g/l, CuCl2 10.5×10-3 g L-1,
ZnCl2 11.5×10-3g/l, MnCl2 15.0×10-3g/l) and CoCl2 25.0×10-3g/l, with pH 7 was used (Aldrovandi et al.
2009). Anode and cathode were connected to external wiring to complete the
circuit. Voltage and current were measured via multimeter. The electrolytic
solution was exposed to oxygen present in ambient air for the reduction reaction
to occur (Feng et al. 2008; Vignesh and Rani 2012). In anode compartment,
bacterium oxidizes fuel, resulting in production of electrons and protons (Gil
et al. 2003; Gregory et al. 2004). The external circuit applied for electrons
to travel across it and protons get transferred to cathode compartment through
salt bridge. In anode compartment anaerobic micro-environment was maintained throughout
the operation (Lovely et al. 1993). All the MFCs were operated at ambient room
temperature (32 ± 20C).
Statistical Analysis
Voltage and current were recorded
in the open circuit using auto-range digital multimeter (KUSAM-MECO 603), after
each 1hour time interval for three and five consecutive days, for electrode optimization
and isolation studies respectively. All experiments were performed in
triplicate. Descriptive analysis of data and calculations were done by SPSS16
and typical values are presented.
Results and Discussion
Optimization of electrode
One of the major challenges associated
with MFCs is the cost of the electrode material. The present study elucidates
the feasibility of cheaper and easily available materials as an alternative to
expensive and sophisticated electrode material (Kim et al. 1999; Logan 2008;
Singh and Songera 2012). 3 combinations from 4 electrodes that are Zn-C, Zn- Cu and Zn-Al were checked. (Tab.1).
Zn-C electrode combination gave the maximum voltage 1.1±0.02 V and current of
1.5±0.12 mA. The low voltage and current were recorded for the Zn-Al
(0.196±0.070V and 0.311 ±0.147mA).
Table 1: Microbial fuel cell performance with rice
bran oil refinery industry wastewater using three different pair of electrode
combinations.
Zn-Cu
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Zn-C
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Zn-Al
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Voltage
(V)
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Current (mA)
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Voltage (V)
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Current (mA)
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Voltage (V)
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Current (mA)
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0.9031±0.010
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1.251±0.034
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1.128±0.06
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1.728±0.051
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0.057±0.030
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0.099±0.015
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0.876±0.020
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0.980±0.023
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1.099±0.015
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1.317±0.035
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0.249±0.040
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0.242±0.006
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0.876±0.030
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0.779±0.009
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1.032±0.021
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1.462±0.063
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0.283±0.011
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0.593±0.042
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Each setup was repeated 3 times and typical
values are presented as mean±SE.
Isolation of bacteria from anode biofilm
The bacterial strains were
isolated from rice bran oil refinery industry wastewater. Wastewater was
serially diluted using distilled water to make series from 10-1 to
10-9. The dilutions were inoculated on plates containing nutrient
agar medium and incubated for 48 h. Different mixed bacterial colonies were
observed. Bacterial colonies were pure cultured by streak plate method and on
the basis of morphology different types of bacterial strain were observed. The
isolates were characterized on the basis of cultural and physiological
characteristics. The isolates were named as WRS-1 to WRS-7 (in which W stands
for wastewater, R for rice industries and S for the name of the industry from
where wastewater was collected. Present communication reports about one of the
isolate WRS-1. The isolate WRS-1 is found to be gram negative staphylococcus
bacterium and was further subjected to various biochemical characterizations (Fig.
2 and Tab. 2).
Table 2: Biochemical
characterization of newly isolated bacterium WRS-1.
Biochemical Test
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Result
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Lactose Fermentative Test
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Negative
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Dextrose Fermentative Test
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Negative
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Sucrose Fermentative Test
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Negative
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Triple Sugar Iron Agar Test (H2S
Production)
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Negative
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Starch Hydrolysis
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Negative
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Urease Test
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Positive
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Methyl Red
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Negative
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Voges-Proskauer
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Negative
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Indol
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Negative
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Citrate Utilization
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Positive
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Catalase Test
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Positive
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Figure 2: Positive biochemical testes performed by newly
isolated bacterium WRS-1
Bioelectricity production by bacterial isolate WRS-1
The isolate WRS-1 produced near
about 1.105±0.006V and current of 1.252± 0.005mA in mediator-less MFCs using
synthetically designed wastewater (Figure 03). This pattern might be due to
high organic load and easy availability range of organic material in synthetic
wastewater, for growth of bacterial isolate.
Figure 3:
Bioelectricity production from bacterial isolate WRS-1 in mediator-less MFC fed
with synthetically designed wastewater
In an overall mechanism, the
bacterium utilizes organic components of wastewater for their metabolic
activities and generates redox-active molecules that lead to shuttling of
electrons between reduced and oxidized compounds. In anode chamber, oxidation
of fuel takes place which results in generation of electrons (Bond and Lovley
2003). These electrons are further transferred to Zn anode causing the
oxidation of Zn (Zn is converted to Zn2+)when electrons are
discharged and transferred through the external wires (Meshram and Jadhav2017).
The electrons pass across the external load to reach the cathode chamber.
Meanwhile, ambient air is employed as oxygen source at the cathode chamber
where final reduction reaction occurs. Oxygen gets electrochemically reduced
due to movement of H+ ion from anode to cathode through the proton
exchange material and ultimately forming water on the cathode side (Kaushik and
Jadhav2017).
This is assumed that transfer of
electron takes place via physical contact between bacterial cell membrane or a
membrane organelle with the fuel cell anode, because no external redox
mediators have been applied to the electrochemical system that could help in
accomplishing the electron transfer between the cell and anode. It is reported
that release of electrochemically active redox enzymes specifically present in
Cytochromes of outer membrane of intact bacterial cells allow transfer of
electrons to external solid electron acceptor in MFC (Prasad et al. 2007; Bond
and Lovley2003).
Conclusion
Microbial fuel cells (MFCs) are
promising electrochemical systems for direct harvesting of electron from range
of organic compounds. Zn-C electrode combination as anode and cathode is
effective for electricity production. In present study, gram negative
non-fermentative staphylococcus bacterium was isolated which was found to be
electrogenic. The isolate may also be used in many practical applications such
as clearance of organically loaded wastewater from different industrial
effluents.
Conflict of interest
Authors had no conflict of interest.
Acknowledgement
Authors are thankful to
the University Grants Commission, New Delhi (India) for providing financial
support to the scholar under NET-Junior Research Fellowship scheme; and the Department of
Science and Technology, New Delhi for financial support through DIST-FIST
scheme to support to School of Studies in Biotechnology, Pt. Ravishankar Shukla
University, Raipur (C.G.)
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