Fermentation process for continuous production of succinic acid in a fibrous bed bioreactor

• Continuous succinic acid production using FBB by Actinobacillus succinogenes is first reported.
• Succinic acid concentration 55.3 g/L, productivity 2.77 g/L/h and yield 0.8 g/g were achieved with operation time over 18 days.
• Kinetic equation showed that succinic acid 60 g/L might be a critical inhibition concentration.

Succinic acid (SA) was produced from Actinobacillus succinogenes with high cell density by continuous fermentation using fibrous bed bioreactor (FBB). The effects of feeding glucose concentration, dilution rate, and pH on continuous production of SA were examined to achieve an efficient and economical bioprocess. The optimum feeding glucose concentration, dilution rate, and pH were 80 g/L, 0.05 1/h, and 6.0–6.5, respectively. A SA concentration of 55.3 ± 0.8 g/L, productivity of 2.77 ± 0.04 g/L/h, and yield of 0.8 ± 0.02 g/g were obtained, and the continuous fermentation exhibited long-term stability for as long as 18 days (440 h) with no obvious fluctuations in both SA and biomass levels. The Jerusalimsky equation for the specific rate of SA production presented the inhibition phenomenon of the product, demonstrating that 60 g/L SA might be a critical concentration in this continuous FBB system. The results obtained could be beneficial for future fermentor designs and improvements in SA production.