NaOH/AQ预处理对玉米秸秆脱木质素及酶解性能的影响

对玉米秸秆进行氢氧化钠/蒽醌（NaOH/AQ）去木质化预处理，考察了预处理温度、时间和NaOH用量对玉米秸秆脱木质素程度的影响，并探讨了脱木质素程度对提高预处理后物料酶解性能的影响。L₉（3⁴）正交试验得出较适宜预处理工艺条件为：温度160℃，时间60 min，NaOH用量（以绝干原料质量计）2.8%；其他条件为AQ用量0.05%，固液比1：5（g：mL），此时木质素脱除率为75%，酶解后聚糖转化率达到73.79%。随着物料脱木质素程度的提高，其酶解效率相应增加；当木质素脱除率达到一定程度后，预处理后的聚糖转化率达到最大值，继续提高木质素脱除率，聚糖转化率反而降低。响应面优化的酶水解工艺条件为纤维素酶用量30 FPU/g，β-葡萄糖苷酶10 IU/g，反应时间72 h，温度50℃，底物质量分数2.5%，此时还原糖得率为85.62%。对酶解液进行HPLC分析，酶解液中的葡萄糖质量浓度为14.83 g/L，木糖质量浓度为4.83 g/L。XRD分析显示，预处理前后纤维素的晶型没有变化，而结晶度由31.40%提高至46.91%，表明物料中木质素和半纤维素发生了不同程度的溶出。

Effects of NaOH/AQ Pretreatment on Delignification and Enzymatic Digestibility of Corn Stover

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.