水热抽提玉米芯半纤维素结构变化及对酶解行为影响

Structural changes of hemicelluloses from corncob by hydrothermalextraction and its effects on enzymatic hydrolysis behavior

为提高富含木聚糖的农业废弃物再利用-高效制备低聚木糖,该研究以玉米芯为原料,通过水热预处理结合乙醇分级沉淀获得不同组分半纤维素,并利用分子质量测定、糖基结构及红外表征了半纤维素组分的基本特征,研究了半纤维素结构变化及对酶解效果的影响。结果显示,当利用3倍体积的乙醇分离半纤维素时,木聚糖的得率达到最大为48.67%,醇沉获得的各木聚糖组分由木糖、葡萄糖、甘露糖等组成;分支度(木糖/阿拉伯糖)为6.61~16.10,木聚糖的沉淀主要受到木聚糖的分子质量和分支度2个因素的影响。以不同组分进行酶促反应动力学实验结果表明,分子质量分布系数较小同时分支度最小的组分,其K m及V max分别为(5.43±0.31)mg/mL和(154.9±2.33)U/mg,表现出的催化适应性明显高于其他组分,此结果显示分子质量及分支度可能是影响酶解效率的关键因素。

This paper aimed to improve the reuse of xylan-rich agricultural waste-efficient preparation of xylo-oligosaccharides.In this study,corn cob was used as raw material,and different components of hemicellulose were obtained by hydrothermal pretreatment combined with fractional ethanol precipitation and the basic characteristics of hemicellulose components were characterized by molecular weight determination,sugar structure,and infrared spectroscopy.The results showed that when three times the volume of ethanol was used to separate hemicellulose,the yield of xylan reached a maximum of 48.67%,and each xylan component obtained by alcohol precipitation was composed of xylose,glucose,mannose,etc.The branching degree(xylose/arabinose)was found to be 6.61-16.10.The precipitation of xylan was mainly affected by the molecular weight and branching degree.The catalytic adaptability of the enzyme was significantly higher than that of other components,and the results indicated that molecular weight and branching degree might be the key factors affecting the enzymatic hydrolysis efficiency.The results of enzymatic reaction kinetics experiments with different components showed that the K m and V max of the R3 component with the smaller molecular weight distribution coefficient and the smallest degree of branching were(5.43±0.31)mg/ml and(154.9±2.33)U/mg,respectively,showing a catalytic effect.The adaptability was significantly higher than other components,and the results indicated that molecular weight and branching degree maybe the key factors affecting the efficiency of enzymatic hydrolysis.