In focus: microbial fuel cells, some considerations

Abstract

The discovery by M.C. Potter in 1911 that some bacteria can generate electricity in devices called microbial fuel cells (MFCs) opened up a new opportunity in exploitation of microbes' potential; but limited interest was shown for some time. However, since the 1980's research in this area has intensified. MFCs work on the principle that electricigens can oxidise substrates in an anode chamber releasing electrons and protons. The electrons go through an external circuit to a cathode chamber, while protons travel from the anode to the cathode through a membrane that separates the two chambers. Recombination of electrons and protons in the cathodic chamber completes the circuit in presence of an oxidant, typically oxygen.MFCs have promise in a number of areas including bioremediation, electricity production, biosensing and water desalination. To enhance feasibility of MFC technology in biotechnology sectors, a number of challenges need to be overcome. These include selection/design of efficient microbes, electrodes, membranes and chambers; better understanding of the mechanism and improving the process of electron transfer from the microorganisms to the electrodes; integration of MFCs in the wastewater treatment train; extending potential of MFCs from applications in bioremediation to bioproduction; and cost-effective scale-up of the reactors.This 'In-focus' section of the Journal of Chemical Technology and Biotechnology (JCTB) covers a total of six manuscripts (two review papers 1,2 and four original research articles 3-5 ) in microbial fuel cells reporting recent developments in MFC technology.Alleviating the accumulation of xenobiotics in the environment, has been subject to extensive research. However, the use of bioelectrochemical systems (BES) in remediation is a relatively new endeavour. Fernando et al. 1 report in a comprehensive review, the history of electromicrobiology, contaminants treated by MFC, and types of BES used, addressing BES advantages. The review concludes that BES is promising for both in situ and ex situ environmental remediation applications in a sustainable manner. Gomaa et al. 3 address the mechanism of concomitant degradation of the dye Congo red and bioelectricity generation using a recombinant strain of E. coli. Their work shows that although there seems to exist a link between dye decolourisation and COD values in their reactor, the efficiency of the system for generation of electricity is low. This highlights the importance of appropriately engineered efficient strains for multiple desired outputs. In another study investigating multifunctional MFC, Gajda et al. 4 introduce a novel design of MFC exploiting metal-carbon-derived electrocatalyst to generate electricity from human urine. Their system does not require any chemical or external power addition. Wu et al. 5 describe simultaneous electricity generation and wastewater treatment using an Osmotic microbial fuel cell (OsMFC) which integrates MFC with forward osmosis. They examine ten inorganic-based draw solutes for the OsMFC syste...