Succinic Acid Production With <i>Actinobacillus succinogenes</i> –Influence of an Electric Potential on the Intercellular NADH/NAD ⁺ Balance

Bioelectrochemical systems (BESs) offer a sustainable method for chemical production, including the enhanced production of succinic acid. By combining fermentation with BES, it could be possible to achieve sustainable succinic acid production and CO₂ fixation using <i>Actinobacillus succinogenes</i>. In literature, the potential application of BES is commonly associated with increased succinate yields, as it is expected to enhance the availability of NADH, thereby influencing the intracellular nicotinamide adenine dinucleotide (NADH/NAD⁺) balance. However, it remains unclear whether BES can improve NADH regeneration and achieve higher NADH/NAD⁺ ratios across all growth phases of <i>A. succinogenes</i>. This study investigates the impact of an applied electrical potential on the intracellular NADH/NAD⁺ ratio during an electrochemical-assisted fermentation process. Using an adapted high-performance liquid chromatography method with a Supelcosil LC-18-T column, it was demonstrated that NADH availability in BES, particularly during the stationary growth phase, improved by up to 1.98-fold compared to the control. This enhancement in reducing power led to a succinate yield of 0.747 ± 0.01 g g^-1, representing a 15.65% increase compared to a fermentation without electrochemical assistance. These findings support the expectation that the use of BES could enhance the competitiveness of bio-based succinate production.