Available at www.sciencedirect.com http://www.elsevier.com/locate/biombioe Butanol production from wheat straw by simultaneous saccharification and fermentation using Clostridium beijerinckii: Part I—Batch fermentation Nasib Qureshi a,Ã , Badal C. Saha a , Ronald E. Hector a , Stephen R. Hughes b , Michael A. Cotta a a United States Department of Agriculture (USDA), 1 Agricultural Research Service (ARS), National Center for Agricultural Utilization Research (NCAUR), Fermentation Biotechnology Research Unit, 1815 N. University Street, Peoria, IL 61604, USA b USDA, ARS, NCAUR, Bioproducts & Biocatalysis Research Unit, 1815 N. University Street, Peoria, IL 61604, USA article info Article history: Received 18 December 2006 Received in revised form 22 June 2007 Accepted 5 July 2007 Available online 17 August 2007 Keywords: Butanol Acetone–butanol–ethanol (ABE) Wheat straw Clostridium beijerinckii P260 Saccharification Fermentation abstract Five different processes were investigated to produce acetone–butanol–ethanol (ABE) from wheat straw (WS) by Clostridium beijerinckii P260. The five processes were fermentation of pretreated WS (Process I), separate hydrolysis and fermentation of WS to ABE without removing sediments (Process II), simultaneous hydrolysis and fermentation of WS without agitation (Process III), simultaneous hydrolysis and fermentation with additional sugar supplementation (Process IV), and simultaneous hydrolysis and fermentation with agitation by gas stripping (Process V). During the five processes, 9.36, 13.12, 11.93, 17.92, and 21.42 g L À1 ABE was produced, respectively. Processes I–V resulted in productivities of 0.19, 0.14, 0.27, 0.19, and 0.31 g L À1 h À1 , respectively. It should be noted that Process V resulted in the highest productivity (0.31 g L À1 h À1 ). In the control experiment (using glucose), an ABE productivity of 0.30 g L À1 h À1 was achieved. These results suggest that simultaneous hydrolysis of WS to sugars and fermentation to butanol/ABE is an attractive option as compared with more expensive glucose to ABE fermentation. Further develop- ment of enzymes for WS hydrolysis with optimum characteristics similar to fermentation would make conversion of WS to butanol/ABE even more attractive. Published by Elsevier Ltd. 1. Introduction In response to rising gasoline prices, constant conflicts in the oil-supply region of the world, and depletion of fossil fuels, research and commercialization activities directed toward production of renewable fuels and chemicals such as ethanol and butanol have increased. Renewable resources including molasses, corn, whey permeate, wheat straw (WS), corn stover, corn fiber, and other agricultural byproducts have been promoted as potential feedstocks for production of fuels and chemicals. In 2006, 18.6 Â 10 6 m 3 (4.86 billion gallons) of ethanol was produced from corn in the United States for use as a liquid fuel [1]. This amount of ethanol was about 3% of gasoline that was used in the United States as transport fuel (538 Â 10 6 m 3 or 140 billion gallons) in 2006. In the United States, it has been proposed to replace 30% of gasoline by 2030 using renewable resources as substrates. Estimates suggest that up to 15% of gasoline could be replaced by ethanol using corn as a substrate. Further increase in ethanol production will require the use of biomass (WS, rice straw, switch grass, and other agricultural biomass) as substrates. Butanol is a superior fuel to ethanol [2] and an industrial solvent that can be produced from renewable resources (mentioned above) employing a number of organisms including ARTICLE IN PRESS 0961-9534/$ - see front matter Published by Elsevier Ltd. doi:10.1016/j.biombioe.2007.07.004 Ã Corresponding author. Tel.: +1 309 681 6318; fax: +1 309 681 6427. E-mail address: Nasib.Qureshi@ARS.USDA.GOV (N. Qureshi). 1 Mention of trade names or commercial products in this article is solely for the purpose of providing scientific information and does not imply recommendation or endorsement by the US Department of Agriculture. BIOMASS AND BIOENERGY 32 (2008) 168– 175