Effectively converting carbon dioxide into succinic acid under mild pressure with Actinobacillus succinogenes by an integrated fermentation and membrane separation process

The aim of the present study is to develop an effective bioprocess for converting CO2 into succinic acid (SA) with Actinobacillus succinogenes by an integrated fermentation and membrane separation process. CO2 could be effectively converted into SA using NaOH as the neutralizer under the completely closed exhaust pipe case with self-circulation of CO2 in the bioreactor. Meanwhile, the optimal CO2 partial pressure was 0.4 bar. In addition, a 300 kDa ultrafiltration (UF) membrane was preferred for constructing the membrane bioreactor. Moreover, a high conductivity was toxic to the cells during SA biosynthesis. After removing the high concentration salts by in-situ membrane filtration, the SA productivity and CO2 fixation rate increased by 39.2% compared with the batch culture, reaching 1.39 g·L−1·h−1 and 0.52 g·L−1·h−1 respectively. Furthermore, nanofiltration (NF) was suitable for purifying the SA and recovering the residual substrates in the UF permeate for the next fermentation.