Succinic acid (SA), a four-carbon dicarboxylic acid utilized as a platform chemical for valuable industrial products, is a major fermentation product of Actinobacillus succinogenes cells, synthetized during anaerobic metabolism. In this study, cell-recycled continuous fermentation (CRCF) was carried out in order to maximize the appreciably stable biocatalytic activity of SA-producing cells and the growth-associated mode of SA biosynthesis. Stable and long operations of CRCF could be carried out through an efficient decanter system developed in our laboratory, which could effectively separate highly dense microbial cells from the outlet stream. This allowed to overcome the wash-out phenomenon encountered at relatively low dilution rates in conventional continuous fermentation systems without cell recycling. Through careful assessment of the effects of dilution rate, composition of feeding medium, and cell recycling ratio on SA yield via the CRCF process, volumetric SA productivity could be enhanced to 3.86 g/(L·h), an approximately 5.1-fold increase compared to parallel continuous fermentation without cell recycling. A higher dilution rate and a 24% increment in SA production via increased density of active cells inside the bioreactor of the CRCF system were the probable factors inducing such a considerable enhancement in volumetric SA productivity during CRCF. Since volumetric productivity is the most important parameter determining the cost-effectiveness of a given fermentation bioprocess, it is quite evident that CRCF is a promising alternative to conventional batch or continuous fermentation without cell recycling for mass production of SA.

琥珀酸（SA）是一种四碳二羧酸，用作有价值的工业产品的平台化学品，是琥珀酸放线杆菌的主要发酵产物。厌氧代谢过程中合成的细胞。在这项研究中，进行了细胞循环连续发酵（CRCF），以最大程度地提高SA生产细胞的明显稳定的生物催化活性和SA生物合成的生长相关模式。CRCF的稳定和长期运行可以通过我们实验室开发的高效de析器系统进行，该系统可以有效地将高密度微生物细胞与出口流分离。这允许克服常规连续发酵系统中以相对低的稀释率遇到的冲洗现象，而无需细胞再循环。通过仔细评估稀释率，进料培养基组成和细胞循环比对CRCF工艺对SA产量的影响，可以将SA的体积生产率提高到3.86 g /（L·h），与没有细胞回收的平行连续发酵相比，增加了约5.1倍。通过增加CRCF系统​​生物反应器内部活性细胞的密度，SA产生更高的稀释率和24％的SA产量是导致CRCF期间体积SA生产率显着提高的可能因素。由于容积生产率是决定给定发酵生物过程成本效益的最重要参数，因此，很明显，CRCF是常规分批发酵或连续发酵的有希望的替代方法，无需进行细胞回收即可大规模生产SA。通过增加CRCF系统​​生物反应器内部活性细胞的密度，SA产生更高的稀释率和24％的SA产量是导致CRCF期间体积SA生产率显着提高的可能因素。由于容积生产力是决定给定发酵生物过程成本效益的最重要参数，因此很明显，CRCF是有希望的替代传统批量发酵或连续发酵而无需大量回收SA来大规模生产SA的方法。通过增加CRCF系统​​生物反应器内部活性细胞的密度，SA产生更高的稀释率和24％的SA产量是导致CRCF期间体积SA生产率显着提高的可能因素。由于容积生产力是决定给定发酵生物过程成本效益的最重要参数，因此很明显，CRCF是有希望的替代传统批量发酵或连续发酵而无需大量回收SA来大规模生产SA的方法。