The effect of six different conditions of wet oxidation (WO) pretreatment on fractionation and enzymatic convertibility of sugarcane bagasse was investigated. WO resulted in an increase of cellulose content of bagasse as a result of the solubilisation of hemicelluloses and lignin. The highest cellulose content, nearly 70%, was obtained in the pretreatment at 195 degrees C, 15 min and alkaline pH. Pretreatments at 195 degrees C and 15 min solubilised 93-94% of hemicelluloses and 40-50% of lignin, while pretreatment at 185 degrees C, 5 min and alkaline pH solubilised only 30% of hemicelluloses and 20% of lignin. The highest sugar yield in the liquid fraction, 16.1 g/100 g, was obtained at 185 degrees C, 5 min and acidic pH. The highest formation of carboxylic acids, phenols and furaldehydes occurred at 195 degrees C, 15 min and acidic pH. Alkaline pH reduced the formation of furaldehydes, which was irrelevant for most WO conditions. All pretreatment conditions improved the enzymatic convertibility of cellulose. The highest convertibility, 74.9% was achieved in the hydrolysis of the material obtained by pretreatment at 195 degrees C, 15 min and alkaline pH. Some xylan convertibility was also observed. (c) 2006 Elsevier Inc. All rights reserved.