Enhancement of anaerobic lysine production in Corynebacterium glutamicum electrofermentations

It has been suggested that application of electric potential can affect lysine producing fermentations, although experimental evidence is lacking. To study this hypothesis we used the lysine producer Corynebacterium glutamicum ZW04, and we exposed it to 12 different conditions regarding anaerobic gas environment, applied electrode potential (cathodic, open circuit, anodic), redox mediator and nitrate presence. The gas environment was found to play a major role, with CO₂ leading to double the lysine concentrations and yields when compared to N₂. Electrode potentials also played a major role, with reductive conditions doubling the titers and increasing the yields of lysine up to 4 times. Addition of the redox mediator anthraquinone-2-sulfonate (AQ2S) under the presence of CO₂ and reductive conditions led to additional doubling of the titers, although the yields were not altered considerably. This study demonstrates for the first time that cathodic electrode conditions combined with CO₂ and AQ2S as a redox mediator can significantly improve both the yields and the titers of lysine production of a C. glutamicum lysine producing strain, reaching levels that have only been achieved under aerobic conditions.