单 位：
东北林业大学材料科学与工程学院生物质材料科学与技术教育部重点实验室
关键词：
木质纤维;低共熔溶剂;炼制;纤维素酶解;木质素缩合
摘 要：
木质纤维的有效解离是对木质资源进行高附加值利用的前提。近年来兴起的绿色环保、简便易得的低共熔溶剂能有效解离木质纤维,但同时会出现木质素缩合并吸附在纤维素表面的问题,不利于纤维素的后续酶解利用。为探究木质素缩合与纤维素酶解之间的关系,以杨木木粉为原料,选用氯化胆碱/二水草酸低共熔溶剂在110℃下对原料进行加热解离处理,并对分离出的纤维素固含物进行酶解转化。通过扫描电子显微镜、高效液相色谱仪、~(13)C-~1H二维核磁共振波谱仪对固含物的形貌、组分含量及木质素的结构进行了表征。结果表明:经低共熔溶剂处理1 h后,约80.0%的木质素组分被去除,同时半纤维素出现明显降解,纤维素少量被降解;处理时间达到5 h时,纤维素的保留率从处理1 h的91.8%降至处理3 h的72.7%,半纤维素的保留率从20.4%降至6.1%。随着处理时间延长,纤维素表面出现颗粒状木质素吸附物;当处理时间达到5 h时,纤维素表面球形颗粒发生聚合,二维核磁图谱中显示出明显的缩合信号,木质素缩合率上升至50.9%。由于缩合木质素的产生,纤维素的酶解产率从处理3 h时的73.3%下降至5 h的66.6%,相关性分析表明木质素的缩合会限制纤维素酶解效率的提升。
译 名：
Effect of lignin condensation on cellulose enzymatic hydrolysis during deep eutectic solvent fractionation of lignocellulose
作 者：
YU Yanyan;LI Yilin;LOU Yuhan;LIU Yongzhuang;YU Haipeng;Key Laboratory of Bio-based Material Science and Technology (Ministry of Education), Material Science and Engineering College, Northeast Forestry University;
关键词：
lignocellulose;;deep eutectic solvent;;biorefinery;;cellulose enzymatic hydrolysis;;lignin condensation
摘 要：
Efficient fractionation of lignocellulose is the first step towards a high value-added utilization of wood-based resources. Especially in recent years, as advantages of emerging environmental benign and easy to prepare green solvents, deep eutectic solvents were widely used for efficient lignocellulose fractionation. However, it has the problems of lignin condensation and negative adsorption of lignin on the cellulose surface during the lignocellulose fractionation process, which is not conducive to the subsequent enzymatic utilization of the cellulose component. In order to investigate the relationship between the lignin condensation and cellulose enzymatic hydrolysis efficiency, the poplar wood powder was used as raw lignocellulose and treated with an acidic deep eutectic solvent of choline chloride/oxalic acid dihydrate at 110 ℃ for different time durations, and the fractionated cellulose rich solids were subjected to further enzymatic hydrolysis treatment. The morphology and composition analysis of the cellulose rich solids and the substructure of the fractionated lignin were further characterized by the scanning electron microscope, high performance liquid chromatography and two-dimensional ~(13)C-~1H nuclear magnetic resonance spectrometry. The results showed that nearly 80.0% of the lignin component was removed after 1 h of deep eutectic solvent fractionation, and partial degradations of cellulose and hemicellulose were observed. When the deep eutectic solvent fractionation time increased to 5 h, the retention of cellulose component decreased from 91.8% to 72.7%, compared to that of 1 h fractionation, and the retention of hemicellulose component decreased from 20.4% to 6.1%. As the fractionation time increased from 1 to 3 h, massive nanoparticles of possibly condensed lignin appeared on the cellulose surfaces as observed by the scanning electron microscope. When the deep eutectic solvent fractionation time reached 5 h, the lignin nanoparticles on the cellulose surfaces were merged to form larger aggregations, and a clear signal of lignin condensation in the aromatic region was observed in the two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy(2 D HSQC NMR), with an increase in lignin condensation ratio to 50.9%. The glucose yield from the enzymatic hydrolysis of cellulose rich solids decreased from 73.3% at 3 h of fractionation to 66.6% at 5 h of fractionation, possibly due to the formation of condensed lignin or negative adsorption of the condensed lignin on cellulose surfaces. Correlation analysis indicated that the lignin was condensed after acidic deep eutectic solvent fractionation of lignocellulose, and the condensed lignin or negative absorption of the condensed lignin limited the downstream enzymatic hydrolysis efficiency of the fractionated cellulose component.
