P18: Importance of CO2 supply for enhanced production of succinic acid in Actinobacillus succinogenes fermentations

Succinic acid, a four-carbon dicarboxylic acid, is produced as a major fermentation product during anaerobic metabolism by the bacterial cells of Actinobacillus succinogenes. Succinic acid is used in a wide range of applications such as surfactants, detergents, green solvents, food and pharmaceutical industries. During the intensive course of strain improvement, biosynthetic capability of succinic acid was observed to be significantly enhanced in almost all of the mutant strains, when CO₂ gas was optimally supplied into the fermentation broth. Therefore, in order to develop a strategy to enhance CO₂ gas mass transfer rate(k_La) in 5L stirred-tank bioreactor fermentations, the enzyme of carbonic anhydrase was supplemented as a medium component into the production medium. Notably, about 95 g/L of succinic acid was obtained in the fermentation process with an optimal amount of carbonic anhydrase, about 40% higher productivity compared to the parallel process with no supplement of the enzyme. In this paper, we will also present the medium optimization data obtained using the efficient statistical methods, such as full factorial design (FFD), steepest ascent methods (SAM) followed by response surface methods (RSM).