Contrast-and-comparison paragraph by Oxana Koshova

Microbial fuel cells: principles of organization and prospects of use

When starting to work with microbial fuel cells (MFCs), the specific characteristics of different cells must be taken into consideration. There are two types of microbial cells – mediator and mediator-less MFCs. Both of them share the same structure: anode and cathode chambers filled with electrolyte and divided by the cation-selective membrane. But the electron transfer from microbial cells of the first type to the electrode is facilitated by mediators such as thionine, methyl viologen, or neutral red; while mediator-less MFCs use electrochemically active bacteria for that purpose. In contrast to the mediator-less MFCs, mediator cells are not safe enough or easily accessible because most of the mediators available are expensive and toxic. At the same time, these devices are well-known and thoroughly examined. Mediator-less MFCs, on the other hand, are a much more recent development and due to this the factors that affect optimum operation, such as the bacteria used in the system, the type of ion membrane, and the system conditions are not particularly well-understood. So the type of microbial cell should be selected carefully according to the peculiarities of the investigation or practical use.

Reference:

http://en.wikipedia.org/wiki/Microbial_fuel_cell