Acid hydrolysis, the most common fiber pretreatment method (Ban et al., 2008), generates significant amounts of sugars from hemicellulose. Besides it is a process relatively cheap (Gnansounou et al., 2005). Sulfuric, hydrochloric, hydrofluoric or acetic acids have been tested as catalysts (Herrera et al., 2003). The process consists on the addition of diluted aqueous acid solution (0.1 to 10 % w/ v) to the ground raw material and hydrolyzing in an autoclave. A solid residue, rich in cellulose and lignin, is formed after acid hydrolysis and subsequently treated with enzymes in order to increase the amounts of fermentable sugars (Tellez-Luis et al., 2002). Kurian et al. (2010) achieved extract with 92 g/L of total sugars from sweet sorghum bagasse treated with sulfuric acid at a concentration of 5 g/kg and treated at 140°C for 30 minutes. Ban et al. (2008) treated the same raw material at a solid — liquid mass ratio of 10% with 80 g phosphoric acid/L at 120°C for 80 minutes. These authors reported 302 g reducing sugars/kg with this pretreatment.