Module I - Reverse Microbial Fuel Cell (rMFC)

Overview

Genetical Approach

Reactor system

Measurement System

Mediators

Design of a electrobiochemical reactor system

To perform our cultivation experiments under well defined conditions it was necessary to design a new bioreactor system. Besides the typically controlled parameters in bioreactors like the oxygen partial pressure, pH-signal, temperature and other parameters, it was indispensable to have the possibility to energize the reactor with a defined current. That is why we decided to build an H-cell reactor. This kind of reactor consits of two compartments which are connected by a glass flange. It is possible to fix a membrane in the middle of the flange connection so that the two compartments are seperated. We used a cation selective Nafion® membrane which allowed the divison of the two compartments into an anode and cathode space.
Figure 1 shows schematically the layout of our design.

Figure 1: Planed design for a H-cell reactor: 1 cathode space with sparger for aeration and a heater coil, 2 anode space with a heater coil 3 caps for the reactor glass bodies which provide several fittings for electrodes, heating, pH- adjustment and sampling, 4 cation selective Nafion® membrane, 5 sealing ring 6 autoclavable high-temp clamp

The H-cell reactor could be used for batch fermentations and is constructed for the electron transfer via a mediator.
That is why we considered an alternative reactor design. The other reactor concept is named scalable "flow cell reactor" (FCR) and allows an continous mode of operation. In this reactor type the electron transfer must be realized by direct electron transfer. That is possible if the cells stay in direct contact to the electrode material. The electron transfer is carried out by cytochromes in the outer membrane. That is why we focused on different types of mediators and the expression of key type cytochromes. The Layout of the SFC is shown in Figure 2.

Figure 2: Planed design for a flow cell reactor (FCR). 1 porous cathode material 2 sealing ring 3 cation selective Nafion® membrane 4 hose nippel 5 porous anode material.