MICROBIAL FUEL CELLS: Can a microbe make electricity from bad wine??
A team of scientists in India demonstrates that a microbe can act as a biocatalyst in a microbial fuel cell and produce electricity. An observation that may bring a breakthrough in green technology...
Fuel cells are devices that produce electricity electrochemically from many different chemicals, such as hydrogen gas and methanol, through catalytic oxidation of the fuel at the positive terminal (anode) and chemical reduction at the negative terminal (cathode). The chemical fuel cell requires metal catalysts at the anode compartments, which are responsible for the oxidation of the fuel and generation of electrons. Microbial fuel cells(MFC) contain microorganisms in the anode compartment. These microorganisms biologically oxidize the organic matter and transfer electrons to the anode compartment. This technology provide a green and environmental friendly, renewable bioelectricity generation from molecules, such as carbohydrates and proteins, as well as complex mixture of organic matter present in human, animal and food-processing waste waters.
{Microbial fuel cell constructed with a microorganism isolated from sugar industry effluent, (D. Prasad, T.K. Sivaram, Sheela Berchmans and V. Yegnaraman, Journal of Power Sources, 160(2006) 991-996)}
We have identified a species of yeast (Hansenula anomala) which can act as a biocatalyst in a microbial fuel cell and produce electricity. The interesting fact about this yeast is that it can undergo direct electron transfer with the anode thereby transferring the electrons generated during metabolism to the anode directly. Glucose is used as the fuel for the MFC. Different types of MFCs are being tried in our lab-batch cells, flow cells, coaxial type cells etc (See photographs). Presently the output is relatively lower compared to chemical fuel cells. There are many issues to be solved such as proper choice of electrode materials, imternal resistance of MFCs, Coulombic efficiency of the electron transfer reactions and scaling up issues.
(Direct electron transfer with yeast cells and construction of a mediatorless fuel Cell, D.Prasad, S.Arun, M.Murugesan, S.Padmanaban, R.S.satyanarayanan, Sheela Berchmans and V.Yegnaraman, Biosensors and Bioelectronics, 22(2007)2604-2610)
Acetobactor aceti, is a ubiquitous microorganisms that are well adapted to sugar and ethanol rich environments. A.aceti form part of the complex natural microbial flora of grapes and wine. The wine industry waste water loaded with unfermented sugars and improperly fermented acetic acid (vinger). Along with this, we can introduce the Gluconobacter roseus for effective utilization of unfermented sugars into alcohol. It can be further converted into acetic acid by the action of A.aceti. The mixture of cell cultures improve the metabolic degradation very effectively. Hence bad wine can produce electricity with the help of these two microorganisms. (R. Karthikeyan, K. Sathishkumar, M. Murugesan, Sheela Berchmans, and V. Yegnaraman Bioelectrocatalysis of Acetobacter aceti and Gluconobacter roseus for Current Generation Environ.Sci.Technol.,2009,43(22)8684-8689).
A thought towards future!!
Glucose on complete oxidation gives rise to 24 electrons. Oxidation of 1 mole of glucose corresponds to 24 faradays of electricity. If we can identify a microorganism that can effectively oxidize glucose and transfer the electrons efficiently to anode, we can revolutionize the energy sector by producing sweet batteries and can even dream of replacing petrol filling stations with glucose filling stations.