RESEARCH AND REVIEWS: JOURNAL OF MICROBIOLOGY AND BIOTECHNOLOGY Microbial Fuel Cells- A Boon or a Ban

Microbial fuel cells utilises waste carbohydrates as fuel. It has the property of not utilising a catalyst or proton exchange membrane and it is thus eco-friendly for treating wastes. Biological fuel cell converts chemical energy directly into electrical energy. They are in light because they act in very mild conditions such as ambient temperature, pressure, and inexpensive catalysts i.e. microorganisms or enzymes. The cell uses manure sludge in the anode compartment and aqueous salt solutions which contain dissolved oxygen. The position of both anode and cathode highly influences fuel cell power performances. There are two types of microbial fuel cell i.e. mediated fuel cell and mediator less fuel cells. The maximum power densities obtained with the cell was 4.21 W/m2. Researchers have also reported of a mediated fuel cell utilising a yoghurt bacteria and methylene blue as mediator. A maximum power density of more than 13 W/m2 is generated. Enriched anodic biofilms have generated power densities of as high as 6.9 W/m2. A drawback with redox enzymes in MFCs is that they cannot take part in direct transfer of electrons with conducting supports hence use mediator are used for the electrical connection of the biocatalyst and the electrode. Several methods are utilised to functionalise the electrode surface with layers consisting of redox enzymes, electro catalysts and biocatalysts that promote electrochemical transformation at the electrode interface. Microorganisms that require a mediator do not have electrochemically active surface proteins to transfer electrons to anode electrode. MFCs that do not use mediator require some more carbohydrates to functions. Metal reducing bacteria example Geobacteraceae family and shewanella genus are mainly used for this type of mediator less fuel cell.