Integration of Succinic Acid and Ethanol Production With Potential Application in a Corn or Barley Biorefinery

Production of succinic acid from glucose by Escherichia coli strain AFP184 was studied in a batch fermentor. The bases used for pH control included NaOH, KOH, NH₄OH, and Na₂CO₃. The yield of succinic acid without and with carbon dioxide supplied by an adjacent ethanol fermentor using either corn or barley as feedstock was examined. The carbon dioxide gas from the ethanol fermentor was sparged directly into the liquid media in the succinic acid fermentor without any pretreatment. Without the CO₂ supplement, the highest succinic acid yield was observed with Na₂CO₃, followed by NH₄OH, and lowest with the other two bases. When the CO₂ produced in the ethanol fermentation was sparged into the media in the succinic acid fermentor, no improvement of succinic acid yield was observed with Na₂CO₃. However, several-fold increases in succinic acid yield were observed with the other bases, with NH₄OH giving the highest yield increase. The yield of succinic acid with CO₂ supplement from the ethanol fermentor when NH₄OH was used for pH control was equal to that obtained when Na₂CO₃ was used, with or without CO₂ supplementation. The benefit of sparging CO₂ from ethanol fermentation on the yield of succinic acid demonstrated the feasibility of integration of succinic acid fermentation with ethanol fermentation in a biorefinery for production of fuels and industrial chemicals.