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林业科学 ›› 2018, Vol. 54 ›› Issue (3): 144-151.doi: 10.11707/j.1001-7488.20180315

• 综述 • 上一篇    下一篇

拉曼光谱在木质素研究中的应用进展

金克霞, 王坤, 崔贺帅, 杨淑敏, 田根林, 刘杏娥, 马建锋   

  1. 国际竹藤中心 北京 100102
  • 收稿日期:2016-06-14 修回日期:2016-07-12 出版日期:2018-03-25 发布日期:2018-04-13
  • 基金资助:
    国家自然科学基金项目(31500497);"十二五"国家科技支撑计划项目(2012BAD54G0103)。

Application of Raman Spectroscopy to the Research on Lignin

Jin Kexia, Wang Kun, Cui Heshuai, Yang Shumin, Tian Genlin, Liu Xing, Ma Jianfeng   

  1. International Centre for Bamboo and Rattan Beijing 100102
  • Received:2016-06-14 Revised:2016-07-12 Online:2018-03-25 Published:2018-04-13

摘要: 随着人类对环境污染和资源危机等问题认识的不断深入,开发利用廉价、可再生、可降解的天然高分子材料日益受到重视。木质素是总量仅次于纤维素的第二大天然高分子材料,是自然界中唯一能提供可再生芳基化合物的非石化资源,木质素及其分子结构研究备受关注。木质素主要由愈创木基(G)、紫丁香基(S)和对羟基苯基(H)3种基本结构单元组成,其存在不仅能够增强植物细胞壁的机械强度,同时也能够防止微生物对细胞壁的侵害,使木质化的植物直立挺拔,不易腐朽。在植物细胞壁中,木质素和半纤维素以共价键形式结合,构成木质素-碳水化合物复合体,其与纤维素微纤丝交联在一起,形成了一个复杂的三维网络结构,这一结构被认为是植物细胞壁天然的抗降解屏障。在生物炼制过程中,木质素在木质纤维原料细胞壁中的分布特点直接影响生物质的转化效率,因此,在原位状态下研究植物细胞壁木质素分子结构、微区分布以及细胞壁水平的溶解规律具有重要意义。在传统湿部化学中,定性或定量研究木质素分子结构普遍采用的是磨木木素和克拉森木素,这2种方法都需要对木质素样品进行物理或化学预处理,不可避免地会改变木质素样品天然状态下的分子结构。尽管传统的光学和电子显微技术能够提供木质素的微区分布信息,但是样品通常需要染色处理,且制样过程繁琐。相比较而言,显微拉曼光谱技术因其无损、快速、高分辨率和高灵敏度等特点在研究大分子结构、区域化学等方面具有得天独厚的优势。本文首先对G、S、H型木质素模型物拉曼光谱特征峰及这些结构单元在生物质原料中的特征峰进行归属,并简要介绍影响木质素拉曼光谱的因素,在此基础上综述该技术在植物细胞壁木质素微区分布和生物质预处理过程中木质素溶解规律等方面的研究进展,最后对该技术在木质素研究领域的发展方向进行展望,以期为植物生理学和生物炼制研究领域,尤其是设计高效的生物质预处理工艺提供新思路和新方法,进而拓宽该技术在生物大分子研究中的应用范围。

关键词: 木质素, 拉曼光谱, 显微拉曼光谱成像, 特征峰归属, 区域化学

Abstract: With deeper understanding of resource crisis and environmental pollution,the development of low-priced, renewable and biodegradable natural polymers is drawing great attention. Lignin is the second-largest amount natural high molecular material, only next to cellulose, and is the only non-fossil natural resource, which can provide renewable aryl compounds. The research on the molecular structure of lignin is therefore arousing more concern. The main constitutive monomeric units of lignin are syringyl (S), guaiacyl (G) and p-hydroxyphenyl (H). Lignin can not only strengthen cell walls but also waterproof and protect them against microorganisms. Lignin and hemicelluloses are covalently linked forming lignin-carbohydrate, which fills the voids between microfibrils, and further creats a highly complex 3-D hierarchy structure as a natural biomass recalcitrance against degradation. In biomass refinery, the distribution of lignin directly affects the biomass conversion efficiency. Therefore, in situ study on the molecular structure, micro-distribution and solution pattern of lignin at cellular level is of great significance. In traditional wet-chemistry, milled wood lignin and Klason lignin are commonly used for quantitative and qualitative investigation of the lignin molecular structure. However, the physical or chemical pretreatments required will inevitably disrupted the native-state molecular structure of lignin samples. Although the general optical and electronic microscopy can provide the information on lignin micro-distribution in plant cell walls, complicated staining and embedding are needed for sample preparation. By comparison, Raman spectroscopy with its features of non-destruction, rapidity, high resolution and high sensitivity shows unique advantage in the studies on the macromolecular structure and topochemistry. In the present review, Raman band assignments of G, S, H lignin units and biomass materials are summarized, and the factors influencing lignin Raman spectra are briefly introduced. Progress of the application of Raman spectroscopy to lignin micro-distribution and cellular level dissolution is discussed in detail. The prospect of Raman spectroscopy in the research on lignin is discussed with new ideas and methods for the plant physiology and biomass refinery, especially the design of highly-efficient biomass pretreatment.

Key words: lignin, Raman spectroscopy, Raman imaging, band assignment, topochemistry

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