BUTANOL PRODUCTION FROM CORN FIBER XYLAN USING CLOSTRIDIUM ACETOBUTYLICUM

Authors: Qureshi, Nasib; Li, Xin Liang; Hughes, Stephen; Saha, Badal; Cotta, Michael

Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2006
Publication Date: 5/30/2006
Citation: Qureshi, N., Li, X., Hughes, S.R., Saha, B.C., Cotta, M.A. 2006. Butanol production from corn fiber xylan using Clostridium acetobutylicum. Biotechnology Progress. 22:673-680.

Interpretive Summary: Acetone butanol ethanol (AB or ABE, or butanol) are products of microbial fermentation. In this fermentation, the culture produces up to 25 g/L AB from sugars in the ratio of 3:6. Butanol, which is a major product of this fermentation, is a useful fuel and chemical and can be produced from glucose, corn, molasses, whey permeate, and wood sugars. Approximately 5 billion lb/year of AB are produced in the US from petrochemical sources. In order to make the process of butanol/AB production more environmentally friendly and economical, substrates such as wood and agricultural byproducts (corn fiber, etc.) could be used. For this reason, attempts were made to produce AB from corn fiber arabinoxylan (CFAX) or hemicellulose (corn fiber component). In order to be able to produce AB from CFAX, the culture was supplemented with xylanase enzymes. Further, a process was developed where CFAX hydrolysis, fermentation, and recovery of ABE were performed in a single reactor. This process appears to be the most economical method to produce AB from lignocellulosic materials. As a result of this research, US corn growers/farmers would benefit from the developed process.

Technical Abstract: Acetone butanol ethanol (ABE) were produced from corn fiber arabinoxylan (CFAX) and CFAX sugars (glucose, xylose, galactose, and arabinose) using Clostridium acetobutylicum P260. In mixed sugar (glucose, xylose, galactose, and arabinose) fermentation, the culture preferred glucose and arabinose over galactose and xylose. Under the experimental conditions, CFAX (60 g/L) was not fermented until either 5 g/L xylose or glucose plus xylanase enzyme were added to support initial growth and fermentation. In this system, C. acetobutylicum produced 9.60 g/L ABE from CFAX and xylose. This experiment resulted in a yield and productivity of 0.41 and 0.20 g/L.h, respectively. In the integrated hydrolysis, fermentation, and recovery process, 60 g/L CFAX and 5 g/L xylose produced 24.67 g/L ABE and resulted in a higher yield (0.44) and a higher productivity (0.47 g/L.h). CFAX was hydrolyzed by xylan hydrolyzing enzymes, and ABE were recovered by gas stripping. This investigation demonstrated that integration of hydrolysis of CFAX, fermentation to ABE, and recovery of ABE in a single system is an economically attractive process. It is suggested that the culture be further developed to hydrolyze CFAX and utilize all xylan sugars simultaneously. This would further increase productivity of the reactor.