Abstract: The optimized conditions of NaOH/AQ pretreatment and the effects of the lignin removing rate on the enzymatic digestibility of the pretreated corn stover were investigated. The optimized conditions of the NaOH/AQ pretreatment obtained by the orthogonal experimental design were the reaction temperature 160℃,the reaction time 60 min, the NaOH dosage(based on the mass of dried material)2.8%,the anthraquinone(AQ) dosage 0.05% and the solid to liquor ratio 1:5(g:mL). Under these conditions,the lignin removing rate reached 75% and the polysaccharides conversion rate of the enzymatic digestibility reached 73.79%. The enzymatic efficiency of the pretreated samples improved with the increase of the lignin removing rate. The maximum polysaccharide conversion rate of the pretreated biomass could be obtained as the lignin removing rate reached some degree and then the polysaccharides conversion rate decreased with the continued increase of the lignin removing rate. The optimized conditions of enzymatic hydrolysis by using response surface experimental design were as follows:the temperature 50℃,the time 72 h,the substrate consistency 2.5%, the cellulase dosage 30 FPU/g and the cellubiase enzyme dosage 10 IU/g. Then the reducing sugar yield was 85.62%. The HPLC analyses showed that the glucose and xylose mass concentrations in the enzymatic hydrolyzates were 14.83 and 4.83 g/L,respectively. The results of XRD showed that the crystal form of cellulose before and after pretreatment didn't change and the crystallinity of the pretreated corn stover was increased to 46.91% from 31.40% because of the dissolving of lignin and hemicellulose.

Key words: corn stover, NaOH/AQ pretreatment, enzymatic hydrolysis, polysaccharide conversion rate