Del Río José C, Prinsen Pepijn, Cadena Edith M, Martínez Ángel T, Gutiérrez Ana, Rencoret Jorge
Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, P.O. Box 1052, 41080, Seville, Spain.
Centro de Investigaciones Biológicas, CSIC, Ramiro de Maeztu 9, 28040, Madrid, Spain.
Planta. 2016 May;243(5):1143-58. doi: 10.1007/s00425-016-2470-1. Epub 2016 Feb 5.
Two types of lignins occurred in different lignin-carbohydrate fractions, a lignin enriched in syringyl units, less condensed, preferentially associated with xylans, and a lignin with more guaiacyl units, more condensed, associated with glucans. Lignin-carbohydrate complexes (LCC) were isolated from the fibers of sisal (Agave sisalana) and abaca (Musa textilis) according to a plant biomass fractionation procedure recently developed and which was termed as "universally" applicable to any type of lignocellulosic material. Two LCC fractions, namely glucan-lignin (GL) and xylan-lignin (XL), were isolated and differed in the content and composition of carbohydrates and lignin. In both cases, GL fractions were enriched in glucans and comparatively depleted in lignin, whereas XL fractions were depleted in glucans, but enriched in xylans and lignin. Analysis by two-dimensional Nuclear Magnetic Resonance (2D-NMR) and Derivatization Followed by Reductive Cleavage (DFRC) indicated that the XL fractions were enriched in syringyl (S)-lignin units and β-O-4' alkyl-aryl ether linkages, whereas GL fractions have more guaiacyl (G)-lignin units and less β-O-4' alkyl-aryl ether linkages per lignin unit. The data suggest that the structural characteristics of the lignin polymers are not homogeneously distributed within the same plant and that two different lignin polymers with different composition and structure might be present. The analyses also suggested that acetates from hemicelluloses and the acyl groups (acetates and p-coumarates) attached to the γ-OH of the lignin side chains were extensively hydrolyzed and removed during the LCC fractionation process. Therefore, caution must be paid when using this fractionation approach for the structural characterization of plants with acylated hemicelluloses and lignins. Finally, several chemical linkages (phenylglycosides and benzyl ethers) could be observed to occur between lignin and xylans in these plants.
两种类型的木质素存在于不同的木质素-碳水化合物组分中，一种富含紫丁香基单元、缩合程度较低、优先与木聚糖结合的木质素，以及一种具有更多愈创木基单元、缩合程度更高、与葡聚糖结合的木质素。根据最近开发的一种植物生物质分级程序，从剑麻（龙舌兰属植物）和马尼拉麻（蕉麻）纤维中分离出木质素-碳水化合物复合物（LCC），该程序被称为“普遍”适用于任何类型的木质纤维素材料。分离出了两种LCC组分，即葡聚糖-木质素（GL）和木聚糖-木质素（XL），它们在碳水化合物和木质素的含量及组成上有所不同。在这两种情况下，GL组分富含葡聚糖且木质素相对较少，而XL组分葡聚糖较少，但富含木聚糖和木质素。二维核磁共振（2D-NMR）分析和衍生化后还原裂解（DFRC）表明，XL组分富含紫丁香基（S）-木质素单元和β-O-4'烷基-芳基醚键，而GL组分每个木质素单元具有更多的愈创木基（G）-木质素单元和更少的β-O-4'烷基-芳基醚键。数据表明，木质素聚合物的结构特征在同一植物内并非均匀分布，可能存在两种组成和结构不同的木质素聚合物。分析还表明，在LCC分级过程中，半纤维素的乙酸酯以及连接在木质素侧链γ-OH上的酰基（乙酸酯和对香豆酸酯）被大量水解并去除。因此，在使用这种分级方法对含有酰化半纤维素和木质素的植物进行结构表征时必须谨慎。最后，在这些植物中可以观察到木质素和木聚糖之间存在几种化学连接（苯基糖苷和苄基醚）。
