Tuesday, May 3, 2011
With the increase of the demand for bio-based fuels and chemicals, there has been much attention given to the performance of different feedstocks. Sweet sorghum (Sorghum bicolor L. Moench) is the only crop providing grain and stem that can be used as substrate for the production of sugar, alcohol, syrup, fodder, fuel, bedding, roofing, fencing and paper. The application of a biorefinery philosophy to bagasse utilization requires its fractionation into its main components: cellulose, hemicelluloses and lignin. The first stage in that process is the pretreatment, in which a considerable part of hemicelluloses is solubilized, and cellulose is activated towards enzymatic hydrolysis. In the present work, sweet sorghum bagasse was pretreated with diluted sulfuric acid to obtain hemicellulosic hydrolysate (liquid fraction) and acid cellulignin (solid fraction) to produce second generation ethanol. Response Surface Methodology (RSM) was carried out to determine the optimal conditions applying a Central Composite Rotational Design (CCRD) with 19 trials. As independent variables were evaluated: solid/liquid ratio (1/3 – 1/6 g/mL), sulfuric acid concentration (0.3 – 1.5 % v/v) and reaction time (20 – 60 min). Experiments were conducted in flasks at 1 atm to optimize the xylose concentration and reduce the generation of sugar degradation products, as furfural and 5-hydroxymethylfurfural (HMF) to use the liquid phase as fermentation medium.