Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2007
Publication Date: 9/1/2007
Citation: Ezeji, T.C., Qureshi, N., Blaschek, H.P. 2007. Production of acetone butanol (AB) from liquefied corn starch, a commercial substrate, using Clostridium beijerinckii coupled with product recovery by gas stripping. Journal of Industrial Microbiology and Biotechnology. 34:771-777. Interpretive Summary: Butanol, a superior liquid fuel to ethanol, can be produced from corn and other agricultural crops using bacterial cultures such as Clostridium beijerinckii or C. acetobutylicum. However, currently it is produced by petrochemical route which is more economical than biological route. Currently, 2.6 billion pounds of butanol are produced in the United States from petrochemicals. In order to produce butanol economically from corn, we developed a process where liquefied corn starch and corn steep liquor (CSL, an economical nutrient source) were used. In this process, butanol was produced in different types of bioreactors and recovered using economical recovery techniques (gas stripping). Using this newly developed process, process efficiency was improved >400%. Bioconversion of liquefied corn starch and CSL in combination with simultaneous product recovery would bring biological production of butanol closer to commercialization. United States corn growers, transportation industry, automobile industry, and U.S. public would benefit from this research.
Technical Abstract: A potential industrial substrate (liquefied corn starch) and nutrients (corn steep liquor, CSL) have been employed for acetone butanol (and ethanol) (AB or ABE) production. Fermentation of liquefied corn starch (60 gL**-1) supplemented with 5.6-6.4% (v/v) CSL solution in a batch process resulted in the production of 18.4 gL**-1 of ABE, comparable to the glucose-yeast extract based medium (control experiment, 18.6 gL**-1 ABE). This suggested that both liquefied corn starch and CSL were successfully utilized by Clostridium beijerinckii BA101 for butanol production. However, the presence of sodium metabisulfite (Na2S2O5) in both liquefied corn starch and CSL is a significant problem as it completely inhibited C. beijerinckii BA101 growth at concentrations >0.5 gL**-1. When ABE was recovered by gas stripping from the fed-batch reactor containing saccharified liquefied corn starch, 81.3 gL**-1 ABE was produced as compared to 18.6 gL**-1 in the control experiment. In this integrated system, 225.8 gL**-1 glucose (487% of control) was consumed. In the absence of product removal, it was not possible for C. beijerinckii BA101 to utilize >46.4 gL**-1 glucose. These studies suggested that it is possible to produce higher levels of ABE (>400%) in a fed-batch reactor containing this commercial substrate and nutrient source (CSL) when the system is integrated with product recovery. These studies are expected to bring butanol production closer to commercialization.