Bacterial colonies on electrode surfaces – known as electro-active biofilms – can generate electricity or, when supplied with electricity, produce valuable chemical products through microbial electrosynthesis. This opens up opportunities for renewable and environmentally friendly biotechnological processes. While some electro-active bacteria are able to form compact biofilms with high cell density within a short amount of time – resulting in high production rates – others can only form a low colony density and need significantly longer to develop their biofilms. In order to make these bacteria accessible for biotechnological applications, thicker and denser biofilms need to be produced. Since these electro-active bacteria are not able to do this on their own, the development of artificial biofilms represents a promising approach. To achieve this, electro-active bacterial cells are embedded into gels, which still allow for substrates and products to get in or out, while fixating the bacterial colonies onto the electrode. This increases biofilm compactness, boosts productivity, and shortens the time required for biofilm formation on the electrode.  

Another challenge for biotechnological applications of these bioelectrochemical systems is the stable long-term operation. One promising way forward is the development of continuous processes. In such systems, fresh nutrients and gases are continuously supplied while products are simultaneously removed. This creates stable, steady process conditions and allows for important process parameters to be precisely controlled. Such conditions enable the determination of important reaction kinetic data. These describe the dependency of reaction rates on different system parameters such as substrate or product concentrations. To date, little knowledge of such correlations is available in the field of bioelectrochemistry.

In this project, the research focus is on the bacterium Clostridium ljungdahlii, a well-studied organism for microbial electrosynthesis. It is able to use electricity and CO₂ from gaseous streams, converting them into valuable chemicals such as acetic acid and ethanol. Reaction kinetic data are used to develop kinetic models that describe and link the bacterial processes with the electrochemical processes. Such models are essential to predict the performance of bioelectrochemical processes and ultimately contribute to the improvement of these systems and make them useable on a larger scale.