Proceedings of The 5 th Annual International Conference Syiah Kuala University (AIC Unsyiah) 2015 In conjunction with The 8 th International Conference of Chemical Engineering on Science and Applications (ChESA) 2015 September 9-11, 2015, Banda Aceh, Indonesia 67 Alkaline Pretreatment Effect on Sweet Sorghum Bagasse for Bioethanol Production Yanni Sudiyani, Eka Triwahyuni, Muryanto, Dian Burhani, Joko Waluyo, Anny Sulaswaty, and Haznan Abimanyu Research Center for Chemistry, Indonesian Institute of Sciences (LIPI), Kawasan PUSPIPTEK Serpong, Tangerang Selatan, 15314, Indonesia; *Corresponding Author: sudiyani@gmail.com Abstract Lignocellulosic material, which consist mainly of cellulose, hemicelluloses and lignin, are among the most promising renewable feedstock for the production of energy and chemicals. The bagasse residue of sweet sorghum can be use utilized as raw material to alternative energy such as bioethanol. Bioethanol production consist of pretreatment, saccharification, fermentation and purification process. The pretreatment process is of great importance to ethanol yield. In the present study, alkaline pretreatment was conducted using a steam explosion reactor at 130 0 C with concentrations of NaOH 6, and 10% (kg/L) for 10, and 30 min. For ethanol production separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) process were conducted with 30 FPU of Ctec2 and Htec2 enzyme and yeast of Saccharomyces cerevisiae. The results shows that maximum cellulose conversion to total glucose plus xylose were found to be greatest with NaOH 10% for 30 min. Maximum ethanol yield 92.19% and high concentration of ethanol 66.88g/L were obtained at SSF condition after 24 h. Key words: Bagasse Sorghum, pretreatment, saccharification,fermentation, bioethanol. Introduction The demand of ethanol as a substitute of gasoline is rapidly increasing due to the recent increase imbalance in oil market and interest in environmental issues. Currently bioethanol which is derived mainly from food crops generate many problems such as net energy losses, green house gas emission, and increased food price. Bioethanol can also be produced from abundant and renewable biomass resources such as agriculture residues, plantation and forest residues and energy crops, are still today a challenging proposition. The Sweet sorghum ( Sorghum bicolor (L.) Moench) is one of the most attractive biomass resources for fuel ethanol production due to its adaptability to adverse conditions and it has high fermentable sugar content in its juice and high yield of green biomass. The juice extracted from the fresh stem is composed sucrose, glucose and fructose can be readily fermented to alcohol, known first generation bioethanol ( G1). The residue after extracting the juice from the sweet sorghum is solid fraction left behind, so-called bagasse is lignocellulosic material, can be hydrolyzed into sugar and further can be fermented to ethanol ( Shen et al ., 2011; Lijun et al ., 2013), and called as second generation bioethanol (G2). In the conversion of lignocellulosic biomass to fuel, the biomass needs to be treated so that the cellulose in the plant fibers is exposed (Kumar et al ., 2009). The major constraint to the development of successful bioconversion process is the physical protection of cellulose by lignin against cellulolytic enzymes (Havannavar et al ., 2007). Therefore, for the utilization of