Submitted to: Review Article
Publication Type: Review article
Publication Acceptance Date: 7/20/2004
Publication Date: 10/1/2004
Citation: Ezeji, T.C., Qureshi, N., Blaschek, H.P. 2004. Butanol fermentation research: upstream and downstream manipulations. The Chemical Record. 4:305-314. Interpretive Summary:
Technical Abstract: An overview of advances in acetone-butanol fermentation research is presented with specific reference to the history of acetone-butanol fermentation, genetic manipulation of the butanol-producing Clostridium beijerinckii NCIMB 8052, as well as upstream and downstream processing. Butanol is a superior fuel to ethanol and can be used in internal combustion engines. Butanol fermentation is an old process and is second to ethanol in importance. In this article, specific reference is made to the development of the hyperamylolytic, hyper-"butanolagenic" C. beijerinckii BA101 strain. Amylolytic enzyme (starch hydrolyzing) production by C. beijerinckii BA101 was 1.8- and 2.5-fold greater than that of the C. beijerinckii NCIMB 8052 strain (parental strain) grown in starch and glucose, respectively. We confirmed the presence of a phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) associated with cell extracts of C. beijerinckii BA101 by glucose phosphorylation by PEP and ATP-dependent glucose phosphorylation. It was found that C. beijerinckii BA101 was defective in PTS activity and that it compensates for this defect with enhanced glucokinase activity, resulting in an ability to transport and utilize glucose during the solventogenic stage. The principal problem associated with acetone-butanol fermentation by C. beijerinckii or C. acetobutylicum is butanol toxicity/inhibition to the culture. To solve this problem, we have attempted various alternative in situ/online techniques of butanol removal including membrane-based systems such as pervaporation, liquid-liquid extraction, and gas stripping. We found that gas stripping and pervaporation appear to be the most promising of the in situ acetone-butanol fermentation and recovery techniques but, in terms of cost-effective industrial applications, gas stripping appears to be the most promising. It is anticipated that these developments will make butanol production an economically viable process thus benefiting U.S. farmers and the consumers.