Wet explosion pretreatment of sugarcane bagasse for enhanced enzymatic hydrolysis Rajib Biswas a,b , H. Uellendahl a , B.K. Ahring a,b, * a Section for Sustainable Biotechnology, Aalborg University Copenhagen, Denmark b Center for Bioproducts and Bioenergy, Washington State University, USA article info Article history: Received 9 April 2013 Received in revised form 20 November 2013 Accepted 29 November 2013 Available online 20 December 2013 Keywords: Lignocellulosic feedstock Sugarcane bagasse Wet explosion pretreatment Enzymatic hydrolysis Fermentable sugars abstract Wet explosion pretreatment of sugarcane bagasse was investigated in pilot-scale with the aim of obtaining the highest possible sugar yield after pretreatment. The temperatures used were 155, 170, 185 and 200  C with or without addition of oxygen (0.6 MPa pressure). Enzymatic hydrolysis of washed solid cakes was carried out using two loadings of enzyme mixtures as enzyme protein (EP) on cellulose was 12.4 and 22.0 g kg 1 . After hydrolysis, a pretreatment temperature of 185  C with oxygen yielded the highest glucose concentration of 573.9  4.5 g kg 1 TS and a glucose yield of 87.4  0.7% of the theoretical maximum value. Pretreatment at 200  C with oxygen exhibited enhanced enzymatic efficiency but lower xylose recovery and formation of the degradation products such as acetate, furfural and HMF of 7.6, 3.3 and 1.0 g L 1 , respectively. In the hydrolysis, the total sugars (gluco- se þ xylose) yielded at 185  C and 200  C with oxygen were 615.9  4.5 and 584.5  3.1 g kg 1 TS, respectively. ª 2013 Published by Elsevier Ltd. 1. Introduction Among the various agricultural and industrial residues, sug- arcane bagasse is one of the most abundant lignocellulosic resources [1,2], especially in tropical countries. The enormous utilization of sugarcane (Saccharum officinarum) for sugar and ethanol production in tropical countries such as Brazil, China and India, generate >500 Mt of bagasse as byproduct every year [2]. Nearly half of the bagasse is used, mainly by direct burning, to generate heat and power for the plant operation [3]. The remaining amount can be used as potential feedstock for bioprocessing in a bolt-on plant to current sugar-based ethanol facilities. Like most other agricultural residues, bagasse is composed of approximately 75% polysaccharides (dry weight basis), which are mainly cellulose and hemicel- lulose. However, a low ash value of 1.9% (dry weight basis) offers numerous advantages compared with others agro- based residues [1]. Bioprocessing of lignocellulosic materials requires a pre- treatment step in order to overcome the biomass recalcitrance for subsequent processing. Pretreatment is one of the most economically expensive steps that hinders the industrial application of lignocellulose-based biorefineries [4e6]. Numerous pretreatment methods, including physical, chemi- cal [7,8], thermal, thermochemical [9,10], and biological [11], have been reported, reviewed and published [4e6,12e14]. In general, the purpose of pretreatment is to disrupt the complex * Corresponding author. Center for Bioproducts and Bioenergy, Washington State University, 2710 University Drive, Richland, WA 99354- 1671, USA. Tel.: þ1 509 372 7683; fax: þ1 509 372 7690. E-mail addresses: bka@wsu.edu, bka@tricity.wsu.edu (B.K. Ahring). URL: http://www.tricity.wsu.edu/cbb/ Available online at www.sciencedirect.com ScienceDirect http://www.elsevier.com/locate/biombioe biomass and bioenergy 61 (2014) 104 e113 0961-9534/$ e see front matter ª 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.biombioe.2013.11.027