Bioelectrochemical reactor

A Bioelectrochemical reactor is a type of bioreactor where bioelectrochemical processes are used to degrade/produce organic materials using microorganisms.[1] This bioreactor has two compartments: The anode, where the oxidation reaction takes place; And the cathode, where the reduction occurs. At these sites, electrons are passed to and from microbes to power reduction of protons, breakdown of organic waste, or other desired processes.[2] They are used in microbial electrosynthesis, environmental remediation, and electrochemical energy conversion. Examples of bioelectrochemical reactors include microbial electrolysis cells, microbial fuel cells, enzymatic biofuel cells, electrolysis cells, microbial electrosynthesis cells, and biobatteries.[3][4]

Principles

Electron current is inherent to 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 attempts 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 reduced. Often soluble electron acceptors are depleted in the microbial environment. The microorganism can also maximize their energy by selecting a good electron donor that can be easily metabolized. These processes are done by extracellular electron transfer (EET).[5] The theoretical free energy change (ΔG) for microorganisms relates directly to the potential difference between the electron acceptor and the donor. However, inefficiencies like internal resistance will decrease this free energy change.[6] The advantage of these devices is their high selectivity in high speed processes limited by kinetic factors.

The most commonly studied species are Shewanella oneidensis and Geobacter sulfurreducens.[7][8] However, more species have been studied in recent years.[9]

On March 25, 2013, scientists at the University of East Anglia were able to transfer electrical charge by allowing bacteria to touch a metal or mineral surface. The research shows that it is possible to 'tether' bacteria directly to electrodes.[10]

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 current generation in microorganisms. Berk and Canfield (1964) didn't build the first microbial fuel cell (MFC) until the 60's.

Currently, the investigation of bioelectrochemical reactors is increasing. These devices have real applications in fields like water treatment,[11] energy production and storage, resources production, recycling and recovery.

Applications

Water Treatment

Bioelectrochemical reactors are finding an application in wastewater treatment settings. Current activated sludge processes are energy- and cost-inefficient due to sludge maintenance, aeration needs, and energy needs. By using a bioelectrochemical reactor that utilizes the concept of trickling filtering, these inefficiencies can be addressed.[12] While processing wastewater using this reactor, nitrification, denitrification, and organic matter removal all take place simultaneously in both aerobic and anaerobic conditions using multiple different microbes located on the anode of the system. Though the processing parameters of the reactor affect the overall composition of each microbe, genus Geobacter and genus Desulfuromonas are frequently found in these applications.[12]

See also

References
  1. Krieg, Thomas; Madjarov, Joana (13 April 2018). "Reactors for Microbial Electrobiotechnology" (PDF). Adv Biochem Eng Biotechnol. 167: 231–272.
  2. Krieg T, Sydow A, Schröder U, Schrader J, Holtmann D (December 2014). "Reactor concepts for bioelectrochemical syntheses and energy conversion". Trends in Biotechnology. 32 (12): 645–55. doi:10.1016/j.tibtech.2014.10.004. PMID 25457389.
  3. Rabaey K, Angenent L, Schroder U, Keller J, eds. (2010). Bioelectrochemical systems : from extracellular electron transfer to biotechnological application. London: IWA Publishing. ISBN 978-1-84339-233-0.
  4. Kuntke P, Smiech KM, Bruning H, Zeeman G, Saakes M, Sleutels TH, et al. (May 2012). "Ammonium recovery and energy production from urine by a microbial fuel cell". Water Research. 46 (8): 2627–36. doi:10.1016/j.watres.2012.02.025. PMID 22406284.
  5. Rabaey K, Angenent L, Schroder U, Keller J, eds. (2010). Bioelectrochemical systems : from extracellular electron transfer to biotechnological application. London: IWA Publishing. ISBN 978-1-84339-233-0.
  6. 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.
  7. Krieg T, Sydow A, Schröder U, Schrader J, Holtmann D (December 2014). "Reactor concepts for bioelectrochemical syntheses and energy conversion". Trends in Biotechnology. 32 (12): 645–55. doi:10.1016/j.tibtech.2014.10.004. PMID 25457389.
  8. Liang Q, Yamashita T, Koike K, Matsuura N, Honda R, Hara-Yamamura H, et al. (November 2020). "A bioelectrochemical-system-based trickling filter reactor for wastewater treatment". Bioresource Technology. 315: 123798. doi:10.1016/j.biortech.2020.123798. PMID 32707501.
  9. Zhang X, Rabiee H, Frank J, Cai C, Stark T, Virdis B, et al. (2020-10-16). "Enhancing methane oxidation in a bioelectrochemical membrane reactor using a soluble electron mediator". Biotechnology for Biofuels. 13 (1): 173. doi:10.1186/s13068-020-01808-7. PMC 7568384. PMID 33088343.
  10. Clean Electricity from Bacteria? Researchers Make Breakthrough in Race to Create 'Bio-Batteries' Sciencedaily, March 25, 2013
  11. Liang Q, Yamashita T, Koike K, Matsuura N, Honda R, Hara-Yamamura H, et al. (November 2020). "A bioelectrochemical-system-based trickling filter reactor for wastewater treatment". Bioresource Technology. 315: 123798. doi:10.1016/j.biortech.2020.123798. PMID 32707501.
  12. Liang Q, Yamashita T, Koike K, Matsuura N, Honda R, Hara-Yamamura H, et al. (November 2020). "A bioelectrochemical-system-based trickling filter reactor for wastewater treatment". Bioresource Technology. 315: 123798. doi:10.1016/j.biortech.2020.123798. PMID 32707501.
  • Sasaki K, Morita M, Sasaki D, Hirano S, Matsumoto N, Ohmura N, Igarashi Y (January 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 S, Hasan M, Aroua MK (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 RK, Flora JR (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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