Bioelectrochemical reactor

Bioelectrochemical reactors are a type of bioreactor where bioelectrochemical processes can take place. They are used in bioelectrochemical syntheses, environmental remediation and electrochemical energy conversion. Examples of bioelectrochemical reactors[1][2] include microbial electrolysis cells, microbial fuel cells and enzymatic biofuel cells and electrolysis cells, microbial electrosynthesis cells, and biobatteries. This bioreactor is divided in two parts: The anode, where the oxidation reaction takes place; And the cathode, where the reduction occurs.

History

In 1911 M. Potter described how microbial conversions could create reducing power, and thus electric current. Twenty years later Cohen (1931) investigated the capacity of bacteria to produce an electrical flow and he noted that the main limitation is the small capacity of microorganism to current generation. It took until the 60's since Berk and Canfield (1964) built the first microbial fuel cell (MFC).

Nowadays the investigation on bioelectrochemical reactors is increasing exponentially. These devices have real applications in fields like water treatment, energy production and storage, resources production, recycling and recovery.

Principles

Electron current is inherent to the microbial metabolism. Microorganisms transfer electrons from an electron donor (lower potential species) to an electron acceptor (higher potential species). If the electron acceptor is an external ion or molecule, the process is called respiration. If the process is internal, electron transfer is called fermentation. The microorganism attempt to maximize their energy gain by selecting the electron acceptor with the highest potential available. In nature mainly minerals containing iron or manganese oxides are being reduced. Often soluble electron acceptors are depleted in the microbial environment. The microorganism can also maximize their energy selecting a good electron donor which can be easily metabolized. These processes are done by extracellular electron transfer (EET).[1] The theoretical energy gain ΔG for microorganisms relates directly the potential difference between the electron acceptor and the donor. But the inefficiencies like internal resistances will decrease this energy gain.[3] The advantage of these devices is their high selectivity and in high speed processes limited by kinetic factors. The most commonly studied species are Shewanella oneidensis and Geobacter sulfurreducens. However, more species have been studied in recent years.

On March 25, 2013, scientists at the University of East Anglia were able to transfer electrical charge by letting the bacteria touch on a metal or mineral surface. The research shows that it is possible to 'tether' bacteria directly to electrodes.[4]

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See also

References
  1. Bioelectrochemical Systems: from extracellular electron transfer to biotechnological application. IWA. 2010. p. 488. ISBN 978-1843392330.
  2. Kuntke, P.; Śmiech, K. M.; Bruning, H.; Zeeman, G.; Saakes, M.; Sleutels, T. H. J. A; Hamelers, H. V. M.; Buisman, C. J. N. (2012). "Ammonium recovery and energy production from urine by a microbial fuel cell". Water Research. 46 (8): 2627–2636. doi:10.1016/j.watres.2012.02.025. PMID 22406284.
  3. Heijnen J.J.; Flickinger M.C.; Drew S.W. (1999). Bioprocess technology: fermentation, biocatalysis and bioseparation. New York: JohnWiley & Sons, Inc. pp. 267–291. ISBN 978-0-471-13822-8.
  4. Clean Electricity from Bacteria? Researchers Make Breakthrough in Race to Create 'Bio-Batteries' Sciencedaily, March 25, 2013
  • Sasaki, Kengo; Morita, Masahiko; Sasaki, Daisuke; Hirano, Shin-Ichi; Matsumoto, Norio; Ohmura, Naoya; Igarashi, Yasuo (2011). "Methanogenic communities on the electrodes of bioelectrochemical reactors without membranes". Journal of Bioscience and Bioengineering. 111 (1): 47–9. doi:10.1016/j.jbiosc.2010.08.010. PMID 20840887.
  • Ghafari, Shahin; Hasan, Masitah; Aroua, Mohamed Kheireddine (2009). "Nitrate remediation in a novel upflow bio-electrochemical reactor (UBER) using palm shell activated carbon as cathode material". Electrochimica Acta. 54 (17): 4164–71. doi:10.1016/j.electacta.2009.02.062.
  • Goel, Ramesh K.; Flora, Joseph R.V. (2005). "Sequential Nitrification and Denitrification in a Divided Cell Attached Growth Bioelectrochemical Reactor". Environmental Engineering Science. 22 (4): 440–9. doi:10.1089/ees.2005.22.440.
  • Watanabe, T; Jin, HW; Cho, KJ; Kuroda, M (2004). "Application of a bio-electrochemical reactor process to direct treatment of metal pickling wastewater containing heavy metals and high strength nitrate". Water Science and Technology. 50 (8): 111–8. doi:10.2166/wst.2004.0501. PMID 15566194.
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