Ethanol Production from Sugarcane Bagasse Using Phosphoric Acid-Catalyzed Steam Explosion

The steam explosion was carried out in the absence (autohydrolysis) and presence of phosphoric acid to evaluate the effects of temperature (180 and 210 degrees C), acid concentration (0 and 19 mg g(-1), dry basis) and pretreatment time (5 and 10 min) on the structure and reactivity of sugarcane bagasse. Glucan recovery was used as the main response factor for pretreatment optimization through a central composite design. Autohydrolysis at 210 degrees C for 10 min had a good pretreatment performance but phosphoric acid catalysis (19 mg g(-1)) resulted in better yields under considerably milder conditions (180 degrees C, 5 min). Hydrolysis of both substrates for 96 h using 8 wt.% total solids and 30 mg g(-1) Cellic (R) CTec2 (Novozymes) provided total glucose yields of 75% in average. The production of cellulosic ethanol was assessed by both separate and simultaneous hydrolysis and fermentation using Saccharomyces cerevisiae. Freeze-drying of pretreatment water solubles reduced the concentration of furfural, hydroxymethylfurfural and acetic acid by more than 80% and this eliminated their inhibitory effect on yeast fermentation.