The literature review provides the relevant information
regarding the MFC technology and will give the reader a comprehensive
understanding of its design, function and potential commercial use in the real
world. This outlines the various aspects of the technology and will explore its
feasibility in industrial applications based on the latest research and
experiments conducted by other researchers in this area.  

2.1 Microbes  

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Firstly, in order to understand the fundamental function of
the MFC, it is important to have a grasp in some of the basic functions of the
bacteria. In essence, bacteria breakdown organic matter and release energy in
the process. Extra attention will be paid to certain bacteria which have the
ability to generate electricity and to transfer electron effectively in the
anode2. This type of bacteria is called Exoelectrogens3, “exo-“for exocellular
and “electrogens” based on the ability to directly transfer electrons to a
chemical or material that is not the immediate electron acceptor. There are
many anaerobic bacteria that can only transfer electrons to soluble compounds
such as nitrate or sulphate (not cell synthesised) that can diffuse across the
cell membrane and into the cell. Exoelectrogenic bacteria are the most suited
to function within an MFC due to their ability to transport electrons outside
of the cell. 

This type of bacteria is useful in mediator-less MFC, a MFC
system which do not require a ‘mediator’ to assist in electron transfer. Some
mediators include, thionin, sulphate/sulphide methylene blue, pyocyanin etc.,
as well as others. 5 

These exoelectrogens can be sourced in a number of places,
according to Du et al, they are found in soil, marine sediment, waste water,
fresh water sediment and activated sludge, which are rich with these
microorganisms.5

A list of tested mediator-less bacteria and their associated
substrates are listed in Table