The aim of this study is to optimize the pretreatment of Alfa fibers Stipa tenacissima for the production of bioethanol second generation. The Alfa is a complex lignocellulosic substrate. It is mainly composed by cellulose (49.09% +/- 0.015), hemicellulose (18.20% +/- 0.3) and lignins (16.25% +/- 0.475). In the current study, process of production of the biofuel was carried out through three successive steps: a pretreatment performed with dilute acid (3%) at 120 degrees C during 30 min, an enzymatic saccharification by a commercial enzyme (AP2) and fermentation steps. Dilute acid pretreatment of the biomass resulted in an efficient degradation of cellulose and hemicellulose by increasing the total sugars (39.951 g/L) and reducing sugars (22.36 g/L) yields. These yields were increased after enzymatic saccharification to reach 22.7 g/L of reducing sugars. The fermentation of the aforementioned hydrolysate was efficient with ethanol production being 36.36% of theoretical maximum. (C) 2016 Elsevier Ltd. All rights reserved.