The sono-assisted alkaline pretreatment of sugarcane bagasse was optimized using a central composite design in which the glucose recovery after enzymatic hydrolysis was used as the response function. Cellic (R) CTec3 (Novozymes) and Thermossac (R) Dry (Lallemand) were used for enzymatic hydrolysis and fermentation, respectively. The best performance was achieved at 70 degrees C with 140 W of sonication power using 0.125 g of NaOH g(-1) of dry biomass, yielding a total glucose recovery of 95.8 wt% in relation to the total glucan content of the original material. The fermentation efficiency of the best substrate hydrolysate was 91.4%, whereas lower values of 87.1 and 80.0% were obtained for steam-exploded and sono-assisted alkali-washed steam-exploded cane bagasse, respectively. In addition, when the glucan recovery of each pretreatment method was taken into account, the total C6 cellulosic ethanol production from the sono-assisted alkali-washed cane bagasse was 20.4 and 40.6% higher than that of the other two pretreatment technologies, respectively. (C) 2015 Elsevier B.V. All rights reserved.