Development of continuous fermentation with cell-recycle for biological succinic acid production

Abstract

Process development and its application of succinate-producing Mannheimia succiniciproducens were studied for the efficient production of succinic acid. At the first, though the experiments for the various initial glucose concentrations were performed for reduction of substrate inhibition, cell growth rates were not changed in this study. With this result, we could conclude that fed-batch cultivation was not fitted well to this strain. Second, experiments for improvement of succinic acid productivity were performed though cell immobilization to the activated carbon. Activated carbon was selected for the support because it was cost-competitive material and productivity was 40.27 g $l^{-1} h^{-1}$ at that time. However working volume was only 25 ml. This factor confirmed that succinic acid productivity can be increased depending on the scale up of cell immobilization system. At the last, continuous fermentation was performed for the improvement of succinic acid productivity. Although its volumetric productivity was 2.02 g $l^{-1} h^{-1}$, cell density was lower than that of batch because of continuous cell washout. Cell-recycle system using hollow fiber membrane was introduced to this system additionally for the higher cell density. However cell-recycle system showed drawbacks such as harmful effect due to the cell debris and membrane blocking. Because of these reasons, bleeding was added to this system and best results were acquired using this system, cell-recycle and bleeding. Volumetric productivity was 4.63 g $l^{-1} h^{-1}$, and it could be lasted for 88 h. It was the value corresponding more than 4 times higher than that of batch culture. Continuous culture and cell-recycle and bleeding system were applied to Mannheimia succiniciproducens LPK7 and its maximum volumetric productivity was 1.30 and 4.25 g $l^{-1} h^{-1}$, respectively. It was concluded that cell-recycle and bleeding system was the best system for the efficient production of succinic ...