BACKGROUND: Bagasse, a kind of agricultural residue having high sugar content, has been considered a promising feedstock to produce bio-ethanol. However, the natural structure of bagasse makes it difficult to use thismaterial to produce bio-ethanol directly. Efficient pretreatment is necessary to break down the natural sealed structure of bagasse and sequential enzymatic hydrolysis can releasemaximum sugars. RESULTS: In order to enhance sugar recovery frombagasse, ethanol-based organosolv auto-catalyzed pretreatment followed by enzyme hydrolysis was investigated in this study. The maximum xylose recovery from the prehydrolysate was 10.31 g per 100 g bagasse, and among them 78.08% existed in the form of xylo-oligosaccharides. The highest glucose recovery in the enzymatic hydrolysate was 40.29 g per 100 g bagasse, representing 92.20% of glucose in the bagasse material. In terms of total sugars (combined xylose and glucose both in prehydrolysate and enzymatic hydrolysate), 56.98 g per 100 g bagasse, representing 83.67% of the total sugars in the bagasse biomass were obtained at 195 degrees C for 30 min with 40% ethanol. Corresponding concentrations of 5-HMF, and furfural in the prehydrolysate were only 0.32 and 0.97 g L-1, respectively, which indicated that detoxification may not be required in the next fermentation step. Besides the sugars, about 84.27% of lignin in the bagasse material can also be recovered in the form of ethanol-lignin or enzymatic hydrolysis lignin. CONCLUSIONS: Ethanol-based organosolv auto-catalyzed pretreatment could enhance the enzymatic digestibility of bagasse due to the removal of hemicelluloses and lignin, to finally realize high sugar recovery frombagasse. (C) 2016 Society of Chemical Industry