(592b) Effect of Exogenous Additives on ABE Fermentation with Clostridium Acetobutylicum

Improving butanol titer, rate, and yield remains a significant challenge in ABE fermentation with Clostridium. This study aims to enhance butanol production and yield by introducing various exogenous additives into ABE fermentation and investigating associated changes in metabolites. The impact of different initial concentrations of folic acid (which aids in nucleic acid and amino acid synthesis, enhancing overall solvent tolerance) and artificial electron carriers, such as benzyl viologen (BV), methyl viologen (MV), neutral red (NR), riboflavin (RF), anthraquinone-2-sulfonate (AQS), anthraquinone-2,6-disulfonate (AQDS), and magnetite nanoparticles, on Clostridium fermentation has been examined.

Among the various electron carriers tested, viologen dyes, specifically BV and MV, were found to significantly increase both butanol titer and yield. This enhancement was attributed to a redirection of metabolic flux towards more reduced metabolites (such as alcohols over acids) through the provision of additional reducing power. The initial concentration of BV and MV, as well as the timing of their addition during fermentation, were optimized.

Supplementation with 100 mg/L MV (added at 36 hours) and 5 mg/L BV (added at 0 hours) led to a notable increase in final butanol concentrations to 14.9 ± 0.6 g/L and 15.2 ± 0.9 g/L, respectively, compared to the control without additives (11.3 ± 0.08 g/L). Correspondingly, butanol yields were 0.26 and 0.29 g/g-glucose utilized in the MV and BV systems, respectively, compared to 0.20 g/g-glucose in the control.

Additionally, metabolic analysis was conducted to explore the effects of additives on intracellular metabolites, providing insights into the potential mechanisms underlying the role of electron carriers in butanol production.