Optimization of Succinic Acid Production from Sweet Potato Powder by Actinobacillus succinogenes

In order to raise yields and reduce production costs, the fermentation medium of succinic acid production by Actinobacillus succinogenes from sweet potato powder. First, the effects of sweet potato powder concentration, MgCO₃ concentration, liquefaction enzyme dose, saccharifying enzyme dose, nitrogen source concentration and fermentation time on succinic acid production were investigated by single factor experiments in this study. Then, the optimum values of the parameters were obtained by orthogonal experiment design. Finally, the optimal fermentation conditions were amplified by 2 L stirred bioreactor. The results showed that mixed nitrogen source (yeast powder:corn steep liquor=1:2) was used as a proper nutrient in the succinic acid production from sweet potato powder. The formula optimization results showed that the important parameters were sweet potato powder, MgCO₃, liquifying enzyme dose, glucoamylase dose and mixed nitrogen source. The optimum condition was as follows: Sweet potato powder 115 g/L, MgCO₃ 60 g/L, liquifying enzyme dose 0.008 KUN-S/g substrate, glucoamylase dose 3.09 AGU/g substrate, mixed nitrogen source 33 g/L. Succinic acid yield reached 69.89 g/L at the optimal condition, which was increased by 64.60% compared to that before optimization (42.46 g/L). Approximately 71.42 g/L of succinic acid content with a yield of 79.87% and a productivity of 0.99 g/(L·h) was obtained after 72 h in a 2 L bioreactor. Therefore, sweet potato powder could be a promising feedstock for the economical and efficient production of succinic acid through fermentation by A. succinogenes.