Enhancement of enzymatic saccharification of bagasse by ethanol-based organosolv auto-catalyzed pretreatment

Abstract

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 this material to produce bio-ethanol directly. Efficient pretreatment is necessary to break down the natural sealed structure of bagasse and sequential enzymatic hydrolysis can release maximum sugars. RESULTS In order to enhance sugar recovery from bagasse, 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 °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 from bagasse. © 2016 Society of Chemical Industry