Department of Fibre and Polymer Technology, Royal Institute of Technology, Kungliga Tekniska Högskolan, Teknikringen 56-58, SE-10044, Stockholm, Sweden.
Plant J. 2013 Apr;74(2):328-38. doi: 10.1111/tpj.12124. Epub 2013 Mar 4.
It is of both theoretical and practical importance to develop a universally applicable approach for the fractionation and sensitive lignin characterization of lignin-carbohydrate complexes (LCCs) from all types of lignocellulosic biomass, both natively and after various types of processing. In the present study, a previously reported fractionation approach that is applicable for eucalyptus (hardwood) and flax (non-wood) was further improved by introducing an additional step of barium hydroxide precipitation to isolate the mannan-enriched LCC (glucomannan-lignin, GML), in order to suit softwood species as well. Spruce wood was used as the softwood sample. As indicated by the recovery yield and composition analysis, all of the lignin was recovered in three LCC fractions: a glucan-enriched fraction (glucan-lignin, GL), a mannan-enriched fraction (GML) and a xylan-enriched fraction (xylan-lignin, XL). All of the LCCs had high molecular masses and were insoluble or barely soluble in a dioxane/water solution. Carbohydrate and lignin signals were observed in (1) H NMR, (13) C CP-MAS NMR and normal- or high-sensitivity 2D HSQC NMR analyses. The carbohydrate and lignin constituents in each LCC fraction are therefore believed to be chemically bonded rather than physically mixed with one another. The three LCC fractions were found to be distinctly different from each other in terms of their lignin structures, as revealed by highly sensitive analyses by thioacidolysis-GC, thioacidolysis-SEC and pyrolysis-GC.
开发一种普遍适用于从各种类型的木质纤维素生物质（包括天然和经过各种加工处理的生物质）中分离和敏感鉴定木质素-碳水化合物复合物（LCC）的方法，具有理论和实际重要性。在本研究中，通过引入氢氧化钡沉淀的额外步骤，进一步改进了先前报道的适用于桉树（硬木）和亚麻（非木材）的分级方法，以便适应软木物种。云杉木材被用作软木样品。如回收产率和组成分析所示，所有木质素都在三个 LCC 级分中回收：一个富含葡聚糖的级分（葡聚糖-木质素，GL）、一个富含甘露聚糖的级分（GML）和一个富含木聚糖的级分（木聚糖-木质素，XL）。所有的 LCC 都具有高分子量，并且在二氧六环/水溶液中不溶或几乎不溶。在（1）H NMR、（13）C CP-MAS NMR 和正常或高灵敏度 2D HSQC NMR 分析中观察到碳水化合物和木质素信号。因此，相信每个 LCC 级分中的碳水化合物和木质素成分是通过化学键合而不是物理混合在一起的。通过高度敏感的硫代酸解-GC、硫代酸解-SEC 和热解-GC 分析，发现三个 LCC 级分在木质素结构方面彼此明显不同。
