响应面优化碱醇预处理麦草酶解效率及木质素组分分离

采用氢氧化钠为催化剂,用乙醇对麦草进行预处理以提高其酶解糖化效率,并对降解溶出的碱醇木质素(AEL)进行回收提纯及结构表征,以实现麦草全组分高值化利用。基于Box-Behnken设计原理,选取预处理温度、碱用量和预处理时间为主要影响因素,采用响应面分析法优化了麦草秸秆碱醇预处理的工艺条件,建立了二次多项式数学模型。结果表明:3个因素对酶解率的影响大小依次为:碱用量>预处理温度>预处理时间。最佳预处理工艺为:预处理温度140℃,碱用量1.19%,预处理时间2.37 h;所得物料在pH4.8、加酶量20 FPU/g纤维素酶和20 IU/g β-葡萄糖苷酶、反应温度50℃的条件下酶解48 h,酶解总糖转化率为96.78%(以酶解底物为基准)。化学组分及扫描电镜分析表明,碱醇预处理可去除84.62%的木质素(以原料为基准),纤维致密结构被破坏,表面出现许多凹陷和裂缝,增加了酶对底物的可及性,提高了酶解效率。采用FT-IR对AEL进行结构表征,结果表明,AEL中除部分C-O-C键和C=O键发生断裂,其他基团得到了较好的保留,AEL作为预处理副产物具有较大的应用价值。

Optimization of the Alkali-ethanol Pretreatment of Wheat Straw for Increasing Enzymatic Hydrolysis Efficiency with Response Surface Methodology and Separation of Lignin Component

The wheat straw was pretreated by alkali ethanol solution to increase the total sugar conversion in enzymatic hydrolysis process,and characterize the change in lignin structure. Based on Box-Behnken design,temperature,mass fraction of alkali and time were chosen as the three important factors with three levels. The process conditions of alkali ethanol solution pretreatment were optimized by response surface methodology,and a second order quadratic equation was established,and the applicability of the model and interaction involved factors on predicting the yield o total sugar conversion was verified. The results indicated that the effects order of three factors on the total sugar conversion were as follows:Mass fraction of alkali,temperature and time. The optimal levels for achieving the highest total sugar conversion were obtained,including temperature of 140℃,mass fraction of alkali of 1.19% and reaction time of 2.37 h. The total sugar conversion reached 96.78% under optimized conditions(on the basis of original enzyme substrates). Chemical composition and scanning electron microscopy analysis showed that 84.62% of lignin was removed through alkali alcohol pretreatment(on the basis of original wheat straw). The compact structure of fiber was damaged,and the pores and cracks formed on the fibril promote the accessibility of substrate and enzyme,and increased the efficiency of enzymatic hydrolysis. The characterize of FT-IR showed that the most groups got better retention except part of the C=O bond and C-O-C bond ruptured. Lignin as a pretreatment byproduct had great potential application value.