Study on reduction of carbon dioxide to produce acetic acid and butyric acid by microbial electrosynthesis with response surface analysis

In this study, we investigated the use of graphene modified carbon felt as a cathode in microbial electrosynthesis (MES) and its impact on the accumulation of acetic acid and butyric acid. Our experimental results show that when the cathodic potential of MES was set to - 0.80 V, the maximum accumulation of acetic acid was 250.04 mg & BULL;L-1, the maximum accumulation of butyric acid was 84.87 mg & BULL;L-1, and the total Coulombic efficiency was 85.31%. By using a response surface model, we were able to determine the optimal reaction conditions for MES, which included a temperature of 29.8 celcius, cathode potential of - 0.78 V, and reaction time of 5.3 d. Under these conditions, the maximum coulombic efficiency was 92.3%, with an error between the predicted and experimental values of less than 3.5%. To further understand the impact of graphene modified carbon felt electrodes on MES, we analyzed the microbial community structure on the surface of MES before and after 10 days of reaction using high-throughput sequencing technology. Our results show that Clostridium accounted for 23.50% of the total flora in the inoculated sludge, and its abundance reached 51.90% of the total flora after 10 days of reaction. The functional annotation of KEGG gene in Clostridium revealed that it contains genes encoding Ack and Buk, which are involved in the synthesis of organic acids, suggesting that these genes play a key role in the formation of acetic acid and butyric acid.