Structure function relationship of electroactive biofilms in microbial fuel and electrolysis cells
This proposal aims at identifying generic process and design rules that allow for the development and application of optimized electroactive biofilms in anode reactions. Hence, we will study the correlation between surface chemistry, biofilm formation and architecture as well as current production in bioelectrochemical systems. Moreover, the effect of electron shuttles on the development and activity of anode biofilms as well as their long-term stability will be studied. The ability of microbes in these electroactive biofilms to use electrodes as the terminal electron acceptor of their respiratory chain can be used in wastewater treatment plants for the sustainable removal of organic carbon or in anode-assisted fermentations. The effectiveness of both systems depends on the achievable current density. However, there is still a lack of fundamental knowledge regarding the effect of electrode-materials and their surface chemistry on electroactive biofilm formation. Moreover, we do not know the architecture of an efficient electroactive biofilm and whether the integration of sustainable electron shuttles in these biofilms can lead to higher current densities over longer periods of time. We suggest that it is possible to identify, study and define general design rules for efficient anode-based processes that are congruent to a wide range of applications. Therefore, we will strive to understand the limitations of anode-based processes and formulate design rules for the evolution of anode biofilms.Professor Stom and his research group (Russia) will study the effects of surface chemistry, surfactants, the degree of hydrophilicity and hydrophobicity, polarization of electrodes and electric field on the kinetics, stability and physiology of biofilm formation on the anode electrodes. The group of Professor Gescher (Germany) will develop methods for integrating mediator molecules into a biofilm matrix in order to obtain higher current densities through thicker active biofilms. Moreover, the group will study the long-term activity of anodic biofilm-catalysts and reasons for process heterogeneities. Both tasks will be evaluated in terms of current production, as well as in by assessing biological activity in various areas of the biofilm. The results will be combined in both groups and will be evaluated by application in wastewater treatment systems (Professor Stom's group), as well as in anode fermentation processes (Professor Gescher's group). Compared to control biofilms, long-term stability and functional activity will be evaluated using anoxic fluorescent markers, transcriptomic and metagenomic analysis, as well as, by the rate of elimination of carbon and the formation of metabolites products. Finally, based on the results achieved during the first 28 months, both research groups will jointly design a scalable reactor to study the applicability of the developed design rules under real(istic) conditions.