Tween 80, Tween 20, PEG 4000 or PEG 6000 was used in combination with ammonium hydroxide for the pretreatment of sugarcane bagasse. Pretreatment was carried out by mixing sugarcane bagasse, ammonium hydroxide (28% v/v solution), and water at a ratio of 1:0.5:20, adding 3% (w/w) surfactant based on the weight of dry biomass, and heating the mixture to 160 C for 1 h. Fibers were hydrolyzed using two concentrations of commercially available enzymes, Spezyme CP and Novozyme 188. The results indicated that PEG 4000 and Tween 80 gave the highest cellulose digestibilities (62%, 66%) and ethanol yields (73%, 69%) as compared to the use of only dilute ammonia (38%, 42%) or water (27%, 26%) as catalysts, respectively. The enhanced digestibilities of non-ionic surfactant dilute ammonia treated biomass can be attributed to delignification and reduction of cellulose crystallinity as confirmed by FTIR, TGA and XRD analysis. (C) 2013 Elsevier Ltd. All rights reserved.