FU Yuejin,YANG Sheng,WANG Fangjun,et al.Structural characterization of lignin from walnut shell[J].Journal of Forestry Engineering,2018,3(03):88-94.[doi:10.13360/j.Issn.2096-1359.2018.03.015]





Structural characterization of lignin from walnut shell
1.中国林业科学研究院木材工业研究所,北京 100091;
2.北京林业大学林木生物质化学北京市重点实验室,北京 100083
FU Yuejin1 YANG Sheng1 WANG Fangjun2 YUAN Tongqi2*
1.Research Institute of Wood Chemistry, Chinese Academy of Forestry, Beijing 100091, China;
2.Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China
核桃壳 木质素 分离 酶水解 结构表征
Walnut shell lignin isolation enzyme hydrolysis structure characterization
核桃加工过程会产生大量核桃壳,而核桃壳中木质素含量较高,可作为潜在商业木质素的来源。为充分利用核桃壳中的木质素,必须了解核桃壳木质素的结构特点。用不同浓度的碱溶液对核桃壳中的木质素进行逐级提取,得到了4种碱木质素,并探索了各浓度梯度下木质素的得率。随后,通过深度酶水解得到了酶解残渣木质素。利用凝胶色谱(GPC)、红外光谱(FT-IR)和二维核磁共振(2D HSQC)技术对分离所得木质素样品的结构进行定性和定量表征。对各木质素样品的纯度及分子结构特点进行综合分析后发现,通过逐级碱提核桃壳得到的碱木质素总得率仅为27.25%,但碱提核桃壳残渣酶水解后得到的酶解残渣木质素的得率却高达62.44%。研究中木质素总得率达到了89.69%,代表性良好。4种碱提木质素样品的相对分子质量(1 930~2 330 g/mol)明显低于酶水解木质素样品的相对分子质量(3 190 g/mol),且所有木质素样品的分子质量分布都相对较窄(Mw/Mn<1.5)。核桃壳木质素为典型的SGH型木质素,该木质素分子中S型单元与G型单元比例相近,且含量远高于H型结构单元。核桃壳木质素中主要联结键为β-O-4'醚键结构、β-β'树脂醇结构及β-5'苯基香豆满结构。研究结果可为核桃壳木质素的高效分离和高值化利用提供理论指导。
Walnut is an important nut distributed throughout more than 50 countries and regions. The planting area and yield of walnut in China are both of the highest amounts in the world. A huge amount of walnut shell will be produced during the processing of walnut. The efficient utilization of this byproduct has received great attention. It is well known that the walnut has a high lignin content, which can be used as a source for high quality lignin. Therefore, a full understanding on the lignin structure of walnut shell is of great necessity. A complete isolation of the native lignin in walnut shell is essential for its characterization. In this study, four lignin fractions were successively extracted from the grinded walnut shell by using alkaline solution with various concentrations. Another type walnut lignin was obtained after enzymatic hydrolysis of the residue remained from the isolation of the alkaline lignins. The chemical composition of these five lignin fractions were analyzed. The structural features of the obtained lignins were also characterized by gel permeation chromatography(GPC), infrared spectroscopy(FT-IR), and two dimension heteronuclear single quantum coherence(2D HSQC)NMR techniques. The results showed that the total yield of the four alkaline lignins was only 27.25%, while the yield of enzyme hydrolysis lignin was 62.44%. The total yield of all the lignin fractions in this study reached 89.69%, which could represent well of the native lignin in walnut shell. The molecular weight of the four alkaline lignins(1 930-2 330 g/mol)were obviously lower than that of the enzyme hydrolysis lignin(3 190 g/mol). In addition, all the five lignin fractions exhibited relatively narrow molecular weight distributions(Mw/Mn<1.5). Both FT-IR and 2D HSQC NMR spectra analyses confirmed that the lignin in walnut shell was SGH-type. All the lignin fractions obtained from the walnut shell showed a predominance of β-O-4' aryl ether linkages followed by β-β' linkages and lower amounts of β-5' linkages. The contents of S- and G-type units in walnut shell lignin were similar with each other, and were significantly higher than that of H-type units. The results of this study could provide useful information for the efficient extraction and value-added applications of walnut shell lignin.


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收稿日期:2017-06-25 修回日期:2017-12-18
基金项目:国家自然科学基金(31670587); 中央高校基本科研业务费专项资金项目(2015ZCQ-CL-02)。
更新日期/Last Update: 2018-05-15