- Jan Herzog - Institute of Bioprocess and Biosystems Engineering -
Over the last decade, the power infrastructure in many countries has begun to change, obtaining an increasing amount of energy from renewable sources every year. However, the power output of sources like windmills and solar panels are not constant, varying throughout the day and also being depend on the weather. For the energy transformation to succeed it is therefore key to store or convert the excess energy during peak times. In addition to storing energy in accumulators or in large pumped-storage power plants, an attractive alternative is its utilization in bioprocesses to electrochemically support microorganisms and to produce value chemicals. The Institute of Bioprocess and Biosystems Engineering (IBB) of the TUHH has developed an All-in-One electrode and corresponding smart electrochemical reactor for biosynthesis, especially for the use of CO2.
The electrode can be integrated directly in any standard bioreactor and can be autoclaved in-situ, turning any standard stirred tank reactor easily into a bioelectrochemical system (BES) (Utesch and Zeng 2018). In this set up, the fermentation broth functions as the working electrode chamber, while the counter electrode chamber is found on the inside of the AiO-electrode (see Figure 1). Extensive development and research have proven that this system, in contrary to the classic so-called H-cell BES, has advantages in many areas. Not only is its application simple but it also has a high efficiency when used for in-situ electrolysis, generating super-fine bubbles of gas. Furthermore, it does not encounter the undesired ion-transfer effect which can occur in other BES setups.
The AiO- electrode has recently been used in various microbial fermentations with industrial relevance. In glycerol fermentations with Clostridium pasteurianum, H2 generated by in-situ electrolysis inside the bioreactor in combination with different redox mediators provided a simple way of shifting product selectivity and enhancing the product yield (Utesch et al. 2019).
Furthermore, electro-fermentations with the yeast Rhodosporidium toruloides showed an improved production of microbial lipids and saturated fatty acids which both could be interesting for future production of cocoa-butter equivalents. In addition, the electrode allowed the reduction of the extracellular redox potential to under -200 mV even under strictly aerobic conditions (Arbter et al. 2019).
Currently, research with the AiO-electrode at the IBB focuses among others on CO2 fixation and the production of industrial relevant chemicals. Within the DFG SPP 2170 Interzell, the IBB in cooperation with the Institute of Microbiology and Biotechnology of the University of Ulm is developing a synthetic co-culture for the production of value chemicals from CO2 with the bacterium Acetobacterium woodii and H2 generated from the AiO-electrode. This process could contribute to the struggle against climate change by converting industrial waste gases into the value chemicals, replacing fossil based chemical feed stocks and using renewable energy sources.
Arbter P, Sinha A, Troesch J, Utesch T, Zeng A-P (2019) Redox governed electro-fermentation improves lipid production by the oleaginous yeast Rhodosporidium toruloides. Bioresource Technology
Utesch T, Sabra W, Prescher C, Baur J, Arbter P, Zeng A-P (2019) Enhanced electron transfer of different mediators for strictly opposite shifting of metabolism in Clostridium pasteurianum grown on glycerol in a new electrochemical bioreactor. Biotechnology and bioengineering 116, 1627–1643
Utesch T, Zeng A-P (2018) A novel All-in-One electrolysis electrode and bioreactor enable better study of electrochemical effects and electricity-aided bioprocesses. Eng. Life Sci. 18, 600–610