ABE fermentation from enzymatic hydrolysate of NaOH-pretreated corncobs Kai Gao, Lars Rehmann* Department of Chemical and Biochemical Engineering, Western University, 1151 Richmond Street, London, Ontario N6A5B9, Canada article info Article history: Received 23 August 2013 Received in revised form 27 February 2014 Accepted 1 March 2014 Available online xxx Keywords: Clostridium saccarobutylicum ABE fermentation Corncobs NaOH pretreatment Enzymatic hydrolysis abstract Acetone butanol ethanol (ABE) was produced from enzymatic-hydrolyzed corncobs by Clostridium saccharobutylicum DSM 13864. Pretreatment of corncobs was carried out with 0.5 mol L 1 NaOH followed by enzymatic hydrolysis. The yield of total reducing sugars was 917 g kg 1 pretreated (de-lignified) and washed corncobs. The hydrolysate was used without sediments removal for ABE fermentation. A solvent production of 19.44 g L 1 with 12.27 g L 1 butanol was obtained from 55.22 g L 1 sugars, resulting in an ABE yield of 350 g kg 1 and a production rate of 0.54 g L 1 h 1 . A control experiment using 55.3 g L 1 mixed sugars resulted in an ABE production of 16.81 g L 1 with 10.26 g L 1 butanol, cor- responding to an ABE yield of 300 g kg 1 and a production rate of 0.47 g L 1 h 1 , indicating that the enzymatic hydrolysates may contain stimulating compounds that can improve the ABE fermentation. ª 2014 Elsevier Ltd. All rights reserved. 1. Introduction Looking beyond corn-based ethanol, there has been renewed interest in fermentative production of butanol. Butanol is a platform chemical and alternative biofuel which has a higher energy density compared to its ethanol counterpart and can also be mixed with petroleum at any ratio [1]. High substrate costs remain a significant bottleneck that precludes large- scale implementations of the ABE fermentation. Lignocellulosic biomass is an abundant, renewable, and underutilized global carbon source [2], however, pretreatment is required prior enzymatic release of fermentable sugars. High crystallinity of cellulose and the presence of lignin minimize enzyme access to cellulose and result in poor yields of fermentable sugars [3]. Alkaline pretreatment is one of several chemical pretreatment technologies that have been intensively investigated. The major effect of alkaline pre- treatment is delignification, thus enhancing the reactivity of the remaining carbohydrates [4]. After enzymatic hydrolysis, a relatively clean sugar stream (mainly glucose and xylose) can be obtained at reasonably high yield with economically rele- vant enzyme dosages [5]. The resulting mixed sugar stream can be a suitable feedstock for biofuel production, especially when targeting butanol via solvent-producing bacteria which, unlike most yeast strains used in ethanol production, can utilize both hexose and pentose [6]. Corncobs (central core of maize ear) are an important lignocellulosic by-product of the sweet corn processing in- dustry and are available in sufficient quantity [7]. Recently, it was reported that the hydrolysis of corncobs could be increased from 16% to near 100% after pretreatment with * Corresponding author. Tel.: þ1 519 661 2111x89008; fax: þ1 519 661 3498. E-mail addresses: rehmann@eng.uwo.ca, lrehmann@uwo.ca (L. Rehmann). Available online at www.sciencedirect.com ScienceDirect http://www.elsevier.com/locate/biombioe biomass and bioenergy xxx (2014) 1 e6 Please cite this article in press as: Gao K, Rehmann L, ABE fermentation from enzymatic hydrolysate of NaOH-pretreated corncobs, Biomass and Bioenergy (2014), http://dx.doi.org/10.1016/j.biombioe.2014.03.002 http://dx.doi.org/10.1016/j.biombioe.2014.03.002 0961-9534/ª 2014 Elsevier Ltd. All rights reserved.