Physicochemical Structural Changes of Poplar and Switchgrass during Biomass Pretreatment and Enzymatic Hydrolysis
Physicochemical Structural Changes of Poplar and Switchgrass during Biomass Pretreatment and Enzymatic Hydrolysis
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DOI：
10.1021/acssuschemeng.6b00603
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发表时间：
2016-09-01
影响因子：
8.4
通讯作者：
Ragauskas, Arthur J.
中科院分区：
文献类型：
--
作者：
Meng, Xianzhi;Sun, Qining;Ragauskas, Arthur J.
由于生物质的顽固性，将木质纤维素转化为单糖用于第二代生物乙醇是复杂的，并且需要在酶水解之前进行预处理阶段。本研究采用Simons染色法测定纤维素可及性，GPC法测定聚合度，FTIR法测定植物细胞壁化学结构，对原生、预处理（酸性和碱性）和部分水解的杨树和柳枝稷进行了表征。预处理后的生物质对酶解的敏感性不能通过纤维素DP和可及性的差异来预测。在水解过程中，最显著的DP减少发生在水解的最开始，DP在这个初始阶段开始以明显较慢的速度下降，这表明存在内端和外端葡聚糖酶的协同作用，有助于“剥落”机制的发生。纤维素的可及性在水解开始时有所增加，达到最大值后开始下降。新鲜酶重启水解实验和可及性数据表明，木质素对纤维素酶的不可逆非特异性结合和酶的位阻等与酶的性质有关的因素可能是反应速率逐渐减慢的原因。
Converting lignocellulosics to simple sugars for second generation bioethanol is complicated due to biomass recalcitrance, and it requires a pretreatment stage prior to enzymatic hydrolysis. In this study, native, pretreated (acid and alkaline) and partially hydrolyzed poplar and switchgrass were characterized by using Simons' staining for cellulose accessibility, GPC for degree of polymerization (DP), and FTIR for chemical structure of plant cell wall. The susceptibility of the pretreated biomass to enzymatic hydrolysis could not be easily predicted from differences in cellulose DP and accessibility. During hydrolysis, the most significant DP reduction occurred at the very beginning of hydrolysis, and the DP began to decrease at a significantly slower rate after this initial period, suggesting an existence of a synergistic action of endo- and exoglucanases that contribute to the occurrence of a "peeling off" mechanism. Cellulose accessibility was found to be increased at the beginning of hydrolysis, after reaching a maximum value then started to decrease. The fresh enzyme restart hydrolysis experiment along with the accessibility data indicated that the factors associated with the nature of enzyme such as irreversible nonspecific binding of cellulases by lignin and steric hindrance of enzymes should be responsible for the gradual slowing down of the reaction rate.