Dissertation Melanie Tabea Knoll - Appendix 6.4: Detachment of biomaterial - OCT and video time lapse

In bioelectrochemical systems (BES), the conversion of chemical energy into electrical energy and vice versa can be catalyzed by electroactive microorganisms. The microorganism-electrode interaction is a key factor that can limit sufficient space-time yield required for industrial applications. Providing the organisms with an artificial scaffold that enhances this interaction compared to the naturally formed biofilm matrix can significantly improve the productivity of these systems. In the context of the dissertation, such a hybrid biomaterial was established by embedding the electroactive model organism Shewanella oneidensis in an agarose hydrogel. The possibility of detaching the hybrid biofilm material should be investigated, as the recovery of the biomaterial could be essential in future application processes and reveal the maximum number of electrons that can be supplied before the material degrades. The latter is an important parameter for the potential application of the biomaterial in bioelectrosynthesis, a process in which organisms grow on the cathode as a source of electrons and energy and where the biomaterial could have similar beneficial effects on productivity to those shown in this thesis for anodic systems. Synthetic biofilm detachment was induced by applying a negative current to a sprayed hydrogel in a BES flow cell reactor. Detachment from two electrode materials, a graphite plate and a graphite felt, was visualized using video recording and optical coherence tomography (OCT). The graphite felt resulted in partial detachment of parts of the biofilm, whereas the graphite plate resulted in complete detachment of the biomaterial as a whole.

The authors declare that a patent application for sprayable, synthetic biofilm hydrogel (patent number 102021105164.9) has been granted. Melanie Tabea Knoll and Johannes Gescher are included in the patent and declare competing interest.