Anodic electro‐fermentation: Anaerobic production of L‐Lysine by recombinant Corynebacterium glutamicum

Abstract

Microbial electrochemical technologies (MET) are promising to drive metabolic processes for the production of chemicals of interest. They provide microorganisms with an electrode as an electron sink or an electron source to stabilize their redox and/or energy state. Here, we applied an anode as additional electron sink to enhance the anoxic metabolism of the industrial bacterium Corynebacterium glutamicum through an anodic electro-fermentation. In using ferricyanide as extracellular electron carrier, anaerobic growth was enabled and the feedback-deregulated mutant Corynebacterium glutamicum lysC further accumulated L-lysine. Under such oxidizing conditions we achieved L-lysine titers of 2.9 mM at rates of 0.2 mmol/L/hr. That titer is comparable to recently reported L-lysine concentrations achieved by anaerobic production under reductive conditions (cathodic electro-fermentation). However unlike other studies, our oxidative conditions allowed anaerobic cell growth, indicating an improved cellular energy supply during anodic electro-fermentation. In that light, we propose anodic electro-fermentation as the right choice to support C. glutamicum stabilizing its redox and energy state and empower a stable anaerobic production of L-lysine.

Characterization of a membrane‐separated and a membrane‐less electrobioreactor for bioelectrochemical syntheses

“…Glucose was consumed over a period of 25 hr and concentrations of up to 70 mM lactate, 10 mM succinate, and 2 mM lysine were produced in the system (Figure b). Specific production rates were 1.7 mmol/g CDW /h lactate, 0.25 mmol/g CDW /h succinate, and 0.047 mmol/g CDW /h lysine, which are in the same range as in the 350 ml system (1.5 mmol/g CDW /h lactate, 0.25 mmol/g CDW /h succinate and 0.076 mmol/g CDW /h lysine) previously reported by Vassilev et al ().…”

“…Finally, the anaerobic bioelectrochemical production of lysine and organic acids using C. glutamicum was performed in the reported electrobioreactor. Comparable results to another electrobioreactor were achieved providing that the designed electrobioreactor is suitable for bioelectrochemical production of chemicals (Vassilev et al, ).…”

“…Previous works showed that anaerobic conversion of glucose to lactate, succinate, and lysine with an engineered C. glutamicum is enhanced by the application of an anode as an external electron acceptor and 1.5 mM ferricyanide used as a mediator (Vassilev et al, ). These investigations were done in self‐made electrobioreactors with a working volume of 350 ml (Lai et al, ; Vassilev et al, ). The counter electrode was separated by a cation exchange membrane and products were in the bulk phase of the electrobioreactor.…”

“…The procedure was described in detail elsewhere (Vassilev et al, ). Briefly, the electrobioreactor was equipped with assembly 2 and operated as described above.…”

Small Current but Highly Productive Synthesis of 1,3‐Propanediol from Glycerol by an Electrode‐Driven Metabolic Shift in Klebsiella pneumoniae L17

“…The interaction between microbes and a carbon electrode has been reported to alter the microbial intracellular redox balance, shifting the conversion process towards a more reduced or oxidized state . Previous studies have shown that electrode‐based regulation triggered a change in the metabolic (carbon) fluxes, and concurrently produced more reduced/oxidized metabolites, such as 3‐hydroxypropionic acid, l ‐lysine, and acetoin . EF provides a potential platform to further improve the titer and yield, particularly for targeted oxidized/reduced products in biochemical reactions, which are difficult to achieve through conventional fermentation …”