Bioethanol production from alkaline-pretreated sugarcane bagasse by consolidated bioprocessing using Phlebia sp. MG-60 Le Duy Khuong a, c , Ryuichiro Kondo b , Rizalinda De Leon a , To Kim Anh c , Kuniyoshi Shimizu b , Ichiro Kamei d, * a Department of Chemical Engineering, Environmental Engineering Programme, University of the Philippines Diliman, Quezon 1011, Philippines b Department of Agro-Environmental Sciences, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan c Department of Microbiology-Biochemistry-Molecular Biology, School of Food Technologyand Biotechnology, Hanoi University of Science and Technology, Hanoi, Vietnam d Department of Forest and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, 1-1 Gakuen-kibanadai-nishi, Miyazaki 889-2192, Japan article info Article history: Received 21 November 2013 Received in revised form 15 December 2013 Accepted 16 December 2013 Available online 4 January 2014 Keywords: Consolidated bioprocessing Sugarcane bagasse White-rot fungi Bioethanol Alkaline pretreatment abstract Optimization of alkaline pretreatment of sugarcane bagasse for consolidated bioprocessing fermentation by the cellulose-fermenting fungus Phlebia sp. MG-60 was studied. The lignin and xylan contents of bagasse were decreased and ethanol production from each pretreated sugarcane bagasse by MG-60 was increased in an alkaline concentration-dependent manner. The fungus produced cellulase and xylanase rapidly over 120 h. When this fungus was cultured with 20 g L 1 of sugarcane bagasse pretreated with NaOH (0.8 wt%, 121  C, 60 min), 4.5 g L 1 ethanol was produced, equivalent to 210 mg ethanol per gram of the original untreated bagasse after 240 h fermentation, giving ethanol yields of 65.7% of the theo- retical maximum. These data suggest that Phlebia sp. MG-60 is a potential candidate for ethanol pro- duction from alkali-pretreated bagasse in a single bioreactor, without enzymatic or chemical hydrolysis. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Sugarcane bagasse (SCB) is one of the most abundant agricul- tural residues in the world, creating 540 million tons of biomass per year (Satyanarayana et al., 2008). For the large-scale biological production of bioethanol, SCB is considered an attractive feedstock because of the concentration and abundance of low-cost raw ma- terials, contributing to the reduction of greenhouse gas emissions and the improvement of food security. SCB typically contains (on a washed and dried basis) approximately 40% cellulose, 24% hemi- celluloses, and 25% lignin (Saha, 2003). However, the primary limitation in SCB use is its high degree of complexity because of its mixed composition of cellulose, hemicelluloses, and lignin in extremely inhomogeneous fibers. Therefore, ethanol production from SCB is often complex, with three main steps, including pre- treatment, saccharification, and fermentation. Pretreatment can loosen the crystalline structure and lignin of SCB, making them more accessible to the saccharification enzymes. It is necessary to reduce the lignin content to facilitate carbohydrate hydrolysis by enzyme systems. Several pretreatment methods have been studied for various biomass sources (Sun and Cheng, 2002; Conde-Mejía et al., 2012; Suhardi et al., 2013), including steam explosion, sol- vent extraction, and thermal pretreatment using acids or bases (Mosier et al., 2005). Pretreatment methods investigated for bagasse include acid pretreatment with various acids (Rodriguez- Chong et al., 2004; Gámez et al., 2006; Cheng et al., 2008; Hernández-Salas et al., 2009) steam explosion (Hernández-Salas et al., 2009), alkali treatment (Hernández-Salas et al., 2009), alkali dewaxing (Peng et al., 2009), biological treatment (Li et al., 2002), wet oxidation (Martín et al., 2007), organic solvent pretreatment (Pasquini et al., 2005; Pereira et al., 2007), and liquid hot water pretreatment (Laser et al., 2002). Although various physical (comminution, hydrothermolysis), chemical (acid, alkali, solvents, ozone), and biological pretreatment methods have been investi- gated over the years (Kumar et al., 2009), thermo-chemical pre- treatment of biomass has been the pretreatment of choice to enhance substrate accessibility for efficient enzymatic hydrolysis (Himmel et al., 2007). Alkaline pretreatment dissolves most of lignin and various uronic acid substitutions responsible for * Corresponding author. Tel./fax: þ81 985 58 7181. E-mail address: kamei@cc.miyazaki-u.ac.jp (I. Kamei). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod 0964-8305/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ibiod.2013.12.008 International Biodeterioration & Biodegradation 88 (2014) 62e68