Corn stover is one of the main agricultural residues being considered as a cellulosic ethanol feedstock. This work evaluated the effectiveness of AFEX (TM)(1) pretreatment for converting corn stover to fermentable sugars, both with and without pre-soaking in hydrogen peroxide. The compositional changes and enzymatic digestibility of AFEX-treated and H-AFEX-treated biomass were investigated. Results showed that most of the polysaccharides remained intact following each of these two methods. Compared with AFEX pretreatment, the H-AFEX process enhanced delignification and enzymatic hydrolysis yields of both glucose and xylose. The maximum glucan and xylan digestibility of H-AFEX process were 87.78% and 90.64%, respectively, and were obtained using 0.7 (w/w) water loading, 1.0 (w/w) ammonia loading, 0.5 (w/w) 30 wt.% hydrogen peroxide loading, and 130 degrees C for 10 min. The results of the present work show that H-AFEX is a feasible pretreatment to improve the enzymatic saccharification of corn stover for bioethanol production. (C) 2013 Elsevier Ltd. All rights reserved.