Monday, April 19, 2010
12-07

Integration of succinic acid and ethanol production with potential application in a corn or barley biorefinery

Nhuan P. Nghiem, Kevin B. Hicks, and David B. Johnston. Crop Conversion Science and Engineering, Eastern Regional Research Center, Agricultural Research Service, USDA, 600 E Mermaid Ln, Wyndmoor, PA 19038

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 CO2 supplied by an adjacent ethanol fermentor using either corn or barley as feedstock was examined. The CO2 gas from the ethanol fermentor was sparged directly into the succinic acid fermentor. Without the CO2 supplement, the highest succinic acid yield was observed with Na2CO3, followed by NH4OH, and lastly by 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. Because CO2 from the ethanol fermentation will be used and sequestered in the succinic acid molecule, rather than using externally-provided Na2CO3, it is possible that life cycle green house gas production will be reduced in the integrated system over that produced by the two systems running independently.     

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