To understand the superior hydrolytic activity after polymorphic conversion from cellulose I to II from the adsorption behaviors of enzymes
To understand the superior hydrolytic activity after polymorphic conversion from cellulose I to II from the adsorption behaviors of enzymes
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从酶的吸附行为了解纤维素I多晶型转化为II后的优异水解活性
DOI：
10.1007/s10570-016-1183-8
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发表时间：
2017-03-01
期刊：
影响因子：
5.7
通讯作者：
Song, Junlong
中科院分区：
文献类型：
--
作者：
Jin, Ersuo;Zhang, Yu;Song, Junlong
纤维素超微结构在纤维素酶结合与活性关系中的作用尚不清楚。本文采用石英晶体微天平（QCM-D）对纤维素酶与不同晶型的纯纤维素Ⅰ、Ⅱ和中间态（Ⅰ/Ⅱ）纤维素底物之间的相互作用进行了研究。首先，制备具有纤维素I、I/II和II的多晶型物的纤维素纳米晶体（CNC）并将其旋涂在QCM传感器上。用XRD检测纤维素基片的结晶度，用AFM检测纤维素基片的形貌。然后，利用里氏木霉产的纤维素酶，分别研究了I、I/II和II型纤维素酶对底物的吸附和水解。结果表明，在15 °C的酶吸附和解吸过程中，CNC-II的吸附容量最低，总吸附质量为179 ng cm− 2，但可逆结合率最高，为33.7%;作为比较，CNC-I和-I/II的值分别为235 ng cm− 2和25.6%，以及207 ng cm− 2和26.9%。由QCM数据得到的CNC-I、CNC-I/II和CNC-II上吸附层的构象依次变软。另一方面，在45 °C下进行酶解实验时，CNC-II在三种底物中表现出最好的酶解能力。结果表明，多晶型转化改变了酶与纤维素表面的亲和性; CNC-II对酶的亲和性最低，但吸附的酶层构象较软，吸附可逆性较强，有利于其水解活性。本文从酶的吸附动力学和吸附层的构象两个方面对纤维素酶的水解活性进行了研究，有助于理解多晶型II纤维素酶的上级水解活性。因此，在酶水解过程中，在减少酶用量和成本方面存在多晶型转化的潜力。
The role of the cellulose ultrastructure on the relationship between cellulase binding and activity is not clear yet. In this article, a quartz crystal microbalance with dissipation (QCM-D) was employed to monitor the interactions between a given cellulase and the cellulose substrates with varied polymorphs of pure cellulose I and II and the intermediate state (I/II). Initially, cellulose nanocrystals (CNCs) with polymorphs of cellulose I, I/II and II were prepared and spin-coated on QCM sensors. The cellulose substrates’ crystallinity degree was examined by XRD, and morphology was detected by AFM. Then, a commercial cellulase fromTrichoderma reeseiwas used to test the adsorption and hydrolysis of cellulose substrates with polymorphs of I, I/II and II, respectively. The results revealed that in the enzyme adsorption and desorption process at a temperature of 15 °C, CNC-II had the lowest adsorption capacity with a total adsorption mass of 179 ng cm−2but the highest reversible binding ratio of 33.7%; for comparison, the values were 235 ng cm−2versus 25.6% and 207 ng cm−2versus 26.9% for CNC-I and -I/II, respectively. And the conformation of adlayers on CNC-I, -I/II and -II derived from the QCM data became softer and softer in turn. On the other hand, CNC-II exhibited the best enzymatic hydrolytic ability among three substrates when enzymatic hydrolysis experiments were conducted at 45 °C. The results indicated that polymorphic conversion from I to II changes the affinity between the enzyme and cellulose surface; CNC-II has the lowest affinity to the enzyme, but the softer conformation of the adsorbed enzyme layer, and the more reversible adsorption may facilitate its hydrolytic activity. This article gives a perspective from the adsorption dynamics and conformation of the adsorbed enzyme layer, helping to understand the superior hydrolytic activity of cellulose with polymorph II. Thus, there is a potential of polymorphic conversion in the reduction of enzyme dosage and cost in the enzymatic hydrolysis process.