Energizing microbes with redox mediators for new bioproductions

In many bioprocesses a broad bioproduct portfolio can currently only be obtained when microorganisms can access oxygen as an electron acceptor. For numerous target substances, however, oxygen is detrimental to product stability and the bioprocess operation. The central aim of e-MICROBe is to innately couple microbial metabolism and electrochemistry via a self-secreted soluble electron mediator to achieve efficient oxygen independent energy metabolism and to directly steer and control metabolism and product formation. This will require creating entirely new physiological traits for production and utilization of redox mediators to generate cellular energy. Thereby, mediators can either act as electron discharge shuttle to enable electro-respiration at an anode or they are employed as inorganic energy donor to deliver electrons from a cathode into the metabolism. We will clarify the underlying reaction pathways in known environmental microorganisms and re-engineer the energy metabolism of common biotech hosts. Thereby, we will switch cellular energy generation from aerobic respiration to anaerobic anodic electro-respiration or from hydrogen consumption as autotrophic electron donor to cathodic electron consumption. The latter process will provide a mechanism to store electrical energy in microbial products. For a new level of in situ insight into microbial energy metabolism, a novel micro-scale bioelectrochemical reactor coupled to microscopic observation and high performance analysis will be developed. With this technique two fundamental concepts for future mediator-based bioprocesses will be evaluated: An all-in-one strategy where one cell is generating the mediators and the targeted product as well as a co-culture system, whereby one cell produces the mediators and a partner cell utilizes them for electro-respiration and product formation. This concept will lay the foundation for a plug-and-play exchange of biotech strains in a mediator-producing co-culture system.