Chemoorganotrophic electrofermentation by Cupriavidus necator using redox mediators

Unraveling the Electron Transfer in Cupriavidus necator – Insights Into Mediator Reduction Mechanics

“…The BES reactor was used in the configuration already described before. [12] In brief, a polished graphite rod (Graphite 24, Germany) with a length of 80 mm and a diameter of 7 mm (geometrical surface area of 18 cm 2 ), held in place by a PTFE rod, served as the working electrode inside the 300 mL DASGIP stirred tank reactor. It was paired with a stainless-steel mesh electrode (1.4404, mesh size 0.1 mm, wire diameter 0.065 mm, Jaera GmbH + Co.KG, Germany) with a geometrical surface area of 20 cm 2 , functioning as the counter electrode.…”

“…Determination of the redox state of the RM in the BES was performed as described before. [12,63] In short, the extinction of the characteristic wavelengths of ferricyanide (320/420 nm) were monitored offline with a spectrophotometer. Reduced ferricyanide does not absorb at 420 nm and can therefore be distinguished from the oxidized form.…”

“…It has already been recognized, that C. necator can interact with ferricyanide and various other mediators. [10][11][12][13] The specific interaction site that engages with ferricyanide or any other mediator in C. necator still remains unclear. The MET process has further been demonstrated with the polymeric redox mediator poly(2-methacryloyloxyethyl phosphorylcholine-co-vinylferrocene) in the presence of oxygen as the main electron acceptor.…”

“…[17] In C. necator, the so far reached current densities via MET are insufficient to replace O 2 entirely. [12] Therefore, methods to enhance mediator reduction rates are needed. A significant bottleneck for MET is the cell membrane itself.…”