Laccase pretreatment of wheat straw: effects of the physicochemical characteristics and the kinetics of enzymatic hydrolysis
Laccase pretreatment of wheat straw: effects of the physicochemical characteristics and the kinetics of enzymatic hydrolysis
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漆酶预处理麦秆：理化特性和酶水解动力学的影响
DOI：
10.1186/s13068-019-1499-3
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发表时间：
2019-06-24
影响因子：
6.3
通讯作者：
Fu, Qian
中科院分区：
文献类型：
--
作者：
Deng, Zhichao;Xia, Ao;Fu, Qian
背景小麦秸秆是我国最丰富的木质纤维素生物质，富含纤维素，可以水解转化为生物燃料，如生物乙醇和生物氢。然而，在木质素的存在下，纤维素的可及性和酶活性大大降低。这显著增加了糖化中的酶成本，这阻碍了木质纤维素生物燃料的工业生产。采用1-羟基苯并三氮唑介导的漆酶处理体系对木质素进行改性和降解，以提高麦草后续的酶解糖化效果。结果傅里叶变换红外光谱（FTIR）分析表明，漆酶介导体系（LMS）处理后，木质素结构特征峰强度发生明显变化。二维核磁共振（NMR）分析表明，芳族醚键断裂，并在LMS处理后，愈创木基（G）被氧化。X射线衍射（XRD）分析表明，木质纤维素的结晶度增加，由于木质素的部分降解。结果表明，酶在木质素上的非生产性吸附减少了28%，而还原糖产率增加了26%。采用半经验动力学模型估算还原糖产率，经LMS预处理的小麦秸秆的初始水解速率（KM）和失活速率系数（α）分别为0.157（h-1）和0.214（h-1）。结论LMS预处理降低了漆酶对木质素的吸附能力。物理化学分析表明，LMS处理后木质素和木质纤维素的化学基团发生了变化，木质纤维素的结晶度增加。利用半经验动力学模型对漆酶处理麦草的水解性能进行了预测，结果表明该模型具有较高的预测精度。
BackgroundWheat straw, the most abundant lignocellulosic biomass in China, is rich in cellulose that can be hydrolyzed and then converted into biofuels, such as bioethanol and biohydrogen. However, the accessibility of cellulose and the enzyme activity are greatly reduced in the presence of lignin. This significantly increases the enzyme cost in the saccharification, which hampers industrial production of lignocellulosic biofuels. In this study, a laccase treatment system mediated by 1-hydroxybenzotriazole was employed to modify and degrade lignin to enhance subsequent enzymatic saccharification of wheat straw. A kinetic model considering enzyme adsorption on lignin was proposed to estimate the saccharification performance.ResultsFourier transform infrared spectroscopy (FTIR) analyses showed that the peak intensity of lignin structure characteristics significantly changed after laccase-mediated system (LMS) treatment. 2D-nuclear magnetic resonance (NMR) analyses indicated that the aromatic ether bonds were cleaved and that guaiacyl (G) was oxidized after LMS treatment. X-ray diffraction (XRD) analyses suggested that the crystallinity of lignocellulose increased due to the partial degradation of lignin. As a result, the nonproductive adsorption of the enzyme on lignin was reduced by 28%, while the reducing sugar yield increased by 26%. A semi-empirical kinetic model was used to estimate the reducing sugar yield, the initial hydrolysis rate (KM) and deactivation rate coefficient (α) of LMS-pretreated wheat straw were 0.157 (h−1) and 0.214 (h−1), respectively. The model showed high accuracy (predicting error < 10%) for describing the behavior of laccase-treated wheat straw hydrolysis when the solid loading is < 5%.ConclusionsThe adsorption ability of the enzyme to lignin was reduced after LMS pretreatment. Physicochemical analyses showed that the chemical groups of lignin and lignocellulose were changed, with the crystallinity of the lignocellulose increasing after LMS treatment. A semi-empirical kinetic model was proposed to estimate the reducing sugar yield, which showed high accuracy for predicting the hydrolysis performance of laccase-treated wheat straw.