ReviewMicrobial catalyzed electrochemical systems: A bio-factory with multi-facet applications
Graphical abstract
Introduction
Microbial catalyzed electrochemical systems (MCES) have emerged as a potential alternative to conventional energy sources for sustainable production of energy and value added products by using microorganisms as biocatalyst. The concept of remodelling microbial metabolism to recover energy and value added products by degradation of organic matter is a flexible and sustainable platform (Venkata Mohan et al., 2013a, Venkata Mohan et al., 2013b, Wang and Ren, 2013). Microbes generally carry out their metabolic activities by utilizing available substrates and generate reducing equivalents [protons (H+) and electrons (e−)]. These e− and H+ move via a series of redox components/carriers (NAD+, FAD, FMN, etc.,) towards an available terminal electron acceptor (TEA), thus generating proton motive force which inturn facilitates generation of energy rich phosphate bonds that are useful for the microbial growth and subsequent metabolic activities. Electrons (e−) in reduced substrate (e.g., carbohydrates, organic acids, etc.) initiate an “electric circuit” that closes the loop with an e− sink furnished by a final electron acceptor (Venkata Mohan et al., 2013b). The function of a MCES is based on harnessing the available electrons by introducing electrodes, as intermediary electron acceptors. Anode chamber, resembles a biofactory that facilitates the generation of reducing equivalents through a series of bio-electrochemical redox reactions under anaerobic microenvironment (Logan, 2010, Zhou et al., 2012, Alister et al., 2012, Venkata Mohan et al., 2007, Venkata Mohan et al., 2008a, Venkata Mohan et al., 2008b, Venkata Mohan et al., 2013a, Venkata Mohan et al., 2013b). MCES are being used to harvest bioelectricity, to remediate complex pollutants in wastewater, to produce various forms of value added products, etc., either in the anode chamber, cathode chamber or in combination (Venkata Mohan et al., 2013a, Venkata Mohan et al., 2013b, Wang and Ren, 2013, Li et al., 2013, Huang et al., 2011). MCES can be customized to achieve multiple-tasks as required due to its feasibility to integrate biodegradation, electrolytic dissociation and electrochemical oxidation/reduction processes in the presence of the solid electron acceptor (anode and cathode) (Venkata Mohan et al., 2009). Essential function of all MCES depends on the electron transfer mechanism and cascade of redox reactions.
Microbial catalyzed electrochemical systems (MCES) based on their functional utility can be broadly classified into microbial fuel cell (MFC), bioelectrochemical treatment system (BET), bioelectrochemical system (BES) and microbial electrolysis cell (MEC) (Sfig. 1). MFC has garnered significant interest in both basic and applied research due to its potential to harness clean energy (Cheng and Logan, 2007, Venkata Mohan et al., 2007, Venkata Mohan et al., 2008a, Venkata Mohan et al., 2008b). MFC has documented its potential to harness electric current from a wide range of soluble or dissolved complex organic wastes/wastewater and renewable biomass as substrate and therefore helps to offset the operational cost of effluent treatment (Venkata Mohan et al., 2013a, Venkata Mohan et al., 2013b, Mohanakrishna et al., 2010a, Mohanakrishna et al., 2010b). MFCs are being viewed as viable and effective treatment units in addition to bioelectricity generation and therefore can be termed as bioelectrochemical treatment (BET) system when the primary focus is towards treatment (Venkata Mohan et al., 2009; Huang et al., 2013, Li et al., 2013, Liu et al., 2014, Velvizhi and Venkata Mohan, 2011). Product recovery is another alternative, where applied potential is used to produce various value added products through microbial electrolysis cell (MEC) and microbial electrosynthesis (MES) process (Rabaey and Rozendal, 2010, Lenin Babu et al., 2013, Venkata Mohan and Lenin Babu, 2011). In the case of MEC, the H+ produced in the anode chamber migrates to the cathode and gets reduced to form H2 in the presence of an e− arrived from the anode, under the influence of a small applied voltage. This facilitates the crossing of endothermic activation energy barrier to form H2 gas. In addition to hydrogen, various other value added products like ethanol, butanol, succinate, etc., can be synthesized at the cathode by applying a small input of voltage (Gong et al., 2013, Marshall et al., 2013, Rabaey and Rozendal, 2010).
In this perspective, the present review delineates the function of Microbial catalyzed electrochemical systems (MCES) pertaining to product recovery and wastewater treatment. Significant development and sustainable research has been reported on BES till date (Sfig. 2). As per the ISI web of knowledge, reports on MCES were sparce from 1998 to 2010, however considerable impact has been noticed henceforth. The first investigation on BET was reported in 1994, but a consistent progress was only observed from 2007 onwards. Microbial electrolysis cells (MEC) which debuted in the year 2006 have been emerging as a potential and useful process for effective biohydrogen production from different substrates. MCES represents a new and promising biological approach for solving the environmental pollution problem and energy crisis with a unified approach. The present review also discusses about exo-electron transfer machinery to understand the electron transfer mechanism in MCES.
Section snippets
Extracellular electron transporting machinery
Transfer of electrons from bacteria to electrode is the primary process that occurs in a MCES. There are three possible ways viz., direct contact, electron shuttling via mediators and through electrically conductive appendages (nanowires/pilin) by which a bacterium can communicate with external electron acceptors (Coursolle et al., 2010; Jiang et al., 2013; Boesen and Nielsen, 2013). Bacteria may exploit one or more of the above mechanisms to transfer electrons extracellularly. In direct
Microbial fuel cell (MFC)
In MFC, an electrical circuit will be established between e– source (bacterial metabolism of substrate) and the e– sink (oxygen)/TEA by placing electrode as an intermediary e– acceptor. It facilities harnessing of bioenergy in the form of bioelectricity by the development of a potential due to the flow of electrons through the circuits. This mechanism facilitates harnessing of energy in the form of bioelectricity during the MFC operation. MFCs facilitate direct conversion of substrate to
Bioelectrochemical treatment system (BET)
MFCs have been conceived and intensively studied as a promising technology for treatment of wastewater which is termed as bioelectrochemical treatment (BET). BET is gaining prominence because it facilitates sustainable wastewater treatment with simultaneous energy generation (Venkata Mohan et al., 2009, Mohanakrishna et al., 2010b, Huang et al., 2011, Aulenta et al., 2013, Velvizhi et al., 2014, Liu et al., 2014). During BET operation, there exists a possibility of integrating diverse
Microbial electrolysis cell (MEC)
Microbial electrolysis cells (MECs) emerged as an alternative route to H2 production from renewable resources (Venkata Mohan and Lenin Babu, 2011, Lenin Babu et al., 2013, Venkata Mohan et al., 2013a). MEC is similar to MFC, but an external potential is applied to facilitate e− and H+ to cross the endothermic barrier to form H2 gas. The H+ migrate to the cathode and get reduced to form H2 in presence of e− travelling from the anode under applied voltage. Standard redox potential for the
Engineering efficient exo-electrogenic strains
Performance of the microbial catalyzed electrochemical systems like MFC, BET, MES, etc., is dependent on the efficiency of the electron transfer machinery. Power output (in MFC), quantity of pollutant treated (in BET) and nature of value added product synthesized (in MES) depends on the electron flux manifested by the bacteria (Venkata Mohan et al., 2013a). Thus it is very important to study the extra cellular electron transfer mechanisms so that losses can be minimized. Generally there are
Current challenges and future perspectives
Research on MCES has been intensified over the the past decade and still requires considerable research inputs from various fields like engineering, microbiology, biochemistry material sciences, electrochemistry, etc. for achieving its full potential for optimizing various parameters affecting its performance. Genetic manipulation of specific proteins involved in electron transfer can help increase the electron transfer by the biocatalyst. Synergistic interaction between the MCES components and
Acknowledgements
The authors wish to thank The Director, CSIR-IICT for encouragement. S.V.M. acknowledges Department of Biotechnology (DBT), Government of India for providing research grant in the framework of National Bioscience Award 2012 (BT/HRD/NBA/34/01/2012(VI)). G.V. and K.V.K. duly acknowledge CSIR for providing research fellowships.
References (93)
- et al.
Mixotrophic operation of photo-bioelectrocatalytic fuel cell under anoxygenic microenvironment enhances the light dependent bioelectrogenic activity
Bioresour. Technol.
(2012) - et al.
A novel sediment microbial fuel cell with a biocathode in the rice rhizosphere
Bioresour. Technol.
(2012) - et al.
Ammonia treatment of carbon cloth anodes to enhance power generation of microbial fuel cells
J. Electrochem. Commun.
(2007) - et al.
Ecologically engineered submerged and emergent macrophyte based system: an integrated eco-electrogenic design for harnessing power with simultaneous wastewater treatment
Ecol. Eng.
(2013) - et al.
Rhizosphere mediated electrogenesis with the function of anode placement for harnessing bioenergy through CO2 sequestration
Bioresour. Technol.
(2012) - et al.
Spontaneous electrochemical removal of aqueous sulfide
Water. Res.
(2008) - et al.
Operation of a bioelectrochemical system as a polishing stage for the effluent from a two-stage biohydrogen and biomethane production process
Biochem Engg J.
(2014) - et al.
Long-term investigation of microbial fuel cells treating primary sludge or digested sludge
Bioresour. Technol.
(2013) - et al.
Bioanodes/biocathodes formed at optimal potentials enhance subsequent pentachlorophenol degradation and power generation from microbial fuel cells
Bioelectrochemistry
(2013) - et al.
Microbial fuel cell type biosensor for specific volatile fatty acids using acclimated bacterial communities
Biosens. Bioelectron.
(2013)
Review nutrients removal and recovery in bioelectrochemical systems: a review
Bioresour. Technol.
Endocrine disruptive estrogens role in electron transfer: bio-electrochemical remediation with microbial mediated electrogenesis
Bioresour. Technol.
Catalytic response of microbial biofilms grown under fixed anode potentials depends on electrochemical cell configuration
Chem. Eng. J.
Influence of catholyte pH and temperature on hydrogen production from acetate using a two chamber concentric tubular microbial electrolysis cell
Int. J. Hydrogen Energy
MFC-cascade stacks maximise COD reduction and avoid voltage reversal under adverse conditions
Bioresour. Technol.
Influence of graphite flake addition to sediment on electrogenesis in a sediment-type fuel cell
Bioresour. Technol.
Animal carcass wastewater treatment and bioelectricity generation in up-flow tubular microbial fuel cells: effects of HRT and non-precious metallic catalyst
Bioresour. Technol.
Bio-electrochemical treatment of distillery wastewater in microbial fuel cell facilitating decolorization and desalination along with power generation
J. Hazard. Mater.
Utilizing acid-rich effluents of fermentative hydrogen production process as substrate for harnessing bioelectricity: an integrative approach
Int. J. Hydrogen. Energy.
Enhanced performance of sulfate reducing bacteria based biocathode using stainless steel mesh on activated carbon fabric electrode
Bioresour. Technol.
Positive anodic poised potential regulates microbial fuel cell performance with the function of open and closed circuitry
Bioresour. Technol.
Microaerophilic microenvironment at biocathode enhances electrogenesis with simultaneous synthesis of polyhydroxyalkanoates (PHA) in bioelectrochemical system (BES)
Bioresour. Technol.
Reductive degradation of chloramphenicol using bioelectrochemical system (BES): a comparative study of abiotic cathode and biocathode
Bioresour. Technol.
High rate membrane-less microbial electrolysis cell for continuous hydrogen production
Int. J. Hydrogen Energy
Biocatalyst behaviour under self-induced electrogenic microenvironment in comparison with anaerobic treatment: evaluation with pharmaceutical wastewater for multi-pollutant removal
Bioresour. Technol.
Electrogenic activity and losses under increasing organic load of recalcitrant pharmaceutical wastewater
Int. J. Hydrogen. Energy.
Anoxic bio-electrochemical system for treatment of complex chemical wastewater with simultaneous bioelectricity generation
Bioresour. Technol.
Dehydrogenase activity in association with poised potential during biohydrogen production in single chamber microbial electrolysis cell
Bioresour. Technol.
Enhanced wastewater treatment efficiency through microbial catalyzed oxidation and reduction: synergistic effect of biocathode microenvironment
Bioresour. Technol.
Sustainable power generation from floating macrophytes based ecological microenvironment through embedded fuel cells along with simultaneous wastewater treatment
Bioresour. Technol.
Bioelectricity generation from chemical wastewater treatment in mediatorless (anode) microbial fuel cell (MFC) using selectively enriched hydrogen producing mixed culture under acidophilic microenvironment
Biochem. Engg. J.
Bioelectricity production from wastewater treatment in dual chambered microbial fuel cell (MFC) using selectively enriched mixed microflora: effect of catholyte
Bioresour. Technol.
Biocatalyzed electrochemical treatment of real field dairy wastewater with simultaneous power generation
Biochem. Eng. J.
Bioelectricity enhancement via overexpression of quorum sensing system in Pseudomonas aeruginosa-inoculated microbial fuel cells
Biosens. Bioelectron.
Treating refinery wastewaters in microbial fuel cells using separator electrode assembly or spaced electrode configurations
Bioresour. Technol.
Pyridine degradation in the microbial fuel cells
J Hazard Mater.
Electricity generation from cattle dung using microbial fuel cell technology during anaerobic acidogenesis and the development of microbial populations
Waste Manage.
Scalable microbial fuel cell (MFC) stacks for continuous real wastewater treatment
Bioresour. Technol.
Rhodopseudomonas palustris purple bacteria fed Arthrospira maxima cyanobacteria: demonstration of application in microbial fuel cells
RSC Adv.
Electrochemical stimulation of microbial cis-dichloroethene (cis-DCE) oxidation by an ethene-assimilating culture
New Biotechnol.
CARD-FISH analysis of a TCE dechlorinating biocathode operated at different set potentials
New Biotechnol.
Molecular dissection of bacterial nanowires
mBio
Bioelectrochemical perchlorate reduction in a microbial fuel cell
Environ. Sci. Technol.
Removal of selenite from wastewater using microbial fuel cells
Biotechnol. letters.
Electricity generation from polyalcohols in single-chamber microbial fuel cells
Biosens. Bioelectron.
Induced catabolic bio-electrohydrolysis of complex food waste by regulating external resistance for enhancing acidogenic biohydrogen production
Bioresour. Technol.
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