Succinic acid production and CO2 fixation using a metabolically engineered Escherichia coli in a bioreactor equipped with a self-inducing agitator

A 5-L bioreactor equipped with a self-induction agitator was applied to a two-stage culture of Escherichia coli NZN111 for succinic acid production in a mineral salts medium. CO2 was cycled inside this reactor and a sufficient CO2 transfer rate was maintained with the elimination of CO2 wasted by ventilation. In the anaerobic stage, much less supplemental CO2 was required at pH 6.3 compared to that at pH 7.0, and the succinate yield increased. The performances of succinate production were little changed when compared to a process with CO2 sparging indicating that use of the self-inducing agitator reduced CO2 waste. The succinate production process was further coupled with ethanol fermentation by using the CO2 produced from ethanol fermentation. This integrated system demonstrated that both succinate and bioethanol can be effectively produced while the emission of the CO2 formed during ethanol fermentation can be greatly reduced.