Submitted to: Applied Biochemistry and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/11/2010
Publication Date: 10/1/2010
Citation: Nghiem, N.P., Hicks, K.B., Johnston, D., 2010. Integration of succinic acid and ethanol production with potential application in a corn or barley biorefinery. Applied Biochemistry and Biotechnology: 162(7):1915. Interpretive Summary: The objective of this research is to develop a biorefinery where fuels and industrial chemicals are produced from renewable resources instead of petroleum-based feedstocks. The fuel in this case is ethanol and the chemical is succinic acid. Succinic acid is a compound that can be used as starting material for production of many important industrial chemicals and consumer products with a potential total annual market of more than $1 billion. The current technology for production of succinic acid is using maleic anhydride or maleic acid, which are petroleum-based feedstocks. We developed an integrated process where some of the carbon dioxide gas produced in corn/barley ethanol fermentation could be used for succinic acid production by a fermentation process using glucose, which can be generated from renewable resources such as corn starch or cellulosic biomass. We demonstrated that the carbon dioxide produced in ethanol fermentation could be used directly without any clean-up needed to remove possible impurities such as oil and moisture. The results clearly demonstrated the feasibility of a biorefinery where a by-product of a process (carbon dioxide gas in ethanol fermentation) can be used to benefit another process (succinic acid production). The incorporation of the carbon dioxide gas from ethanol fermentation into the succinic acid molecule does not stop at its economic benefits. It also has important environmental impacts since it helps remove significant quantities of this greenhouse gas from the atmosphere.
Technical Abstract: 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 pre-treatment. 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 for production of fuels and industrial chemicals. 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.