THE EFFECTS OF REDUCING POWER FROM METAL CARBONATES ON SUCCINIC ACID PRODUCTION USING ACTINOBACILLUS SUCCINOGENES

Bio-succinic acid was first commercialized in 2012 and has a potential to hit $ 15 billion market. Higher conversion or yield in this case, allow bio-succinic acid to be more competitive and could potentially take over the market of other intermediate compound. Redox state of the fermentation medium is reported to have an effect on the metabolic flux and in Actinobacillus succinogenes, one of the best succinic acid producers. It has a direct impact on succinate yield. Therefore, carbonates with different reducing power, CaCO3, NaHCO3, MgCO3, ZnCO3 and (NH4)2CO3 were employed to investigate the effect of their reducing power on succinate yield from glucose. Results showed that a more reducing carbonate, CaCO3 promoted the metabolic flux of A. succinogenes to produce higher reductive metabolite (succinate) to regain its intracellular redox balance. Calcium has a reducing power of 2.87 relative to hydrogen. Ammonium carbonate has an oxidizing power of 0.27, or a negative reducing power relative to hydrogen. Therefore, CaCO3 with a stronger reducing power had a higher succinate yield of 0.68 g/g than (NH4)2CO3 with only 0.14 g/g. On the other hand, MgCO3 had the highest final succinate concentration due to the overall higher sugar consumption by A. succinogenes.