Foster Cliff E, Martin Tina M, Pauly Markus
Great Lakes Bioenergy Research Center, Michigan State University, USA.
J Vis Exp. 2010 Mar 11(37):1745. doi: 10.3791/1745.
The need for renewable, carbon neutral, and sustainable raw materials for industry and society has become one of the most pressing issues for the 21st century. This has rekindled interest in the use of plant products as industrial raw materials for the production of liquid fuels for transportation(1) and other products such as biocomposite materials(7). Plant biomass remains one of the greatest untapped reserves on the planet(4). It is mostly comprised of cell walls that are composed of energy rich polymers including cellulose, various hemicelluloses (matrix polysaccharides, and the polyphenol lignin(6) and thus sometimes termed lignocellulosics. However, plant cell walls have evolved to be recalcitrant to degradation as walls provide tensile strength to cells and the entire plants, ward off pathogens, and allow water to be transported throughout the plant; in the case of trees up to more the 100 m above ground level. Due to the various functions of walls, there is an immense structural diversity within the walls of different plant species and cell types within a single plant(4). Hence, depending of what crop species, crop variety, or plant tissue is used for a biorefinery, the processing steps for depolymerization by chemical/enzymatic processes and subsequent fermentation of the various sugars to liquid biofuels need to be adjusted and optimized. This fact underpins the need for a thorough characterization of plant biomass feedstocks. Here we describe a comprehensive analytical methodology that enables the determination of the composition of lignocellulosics and is amenable to a medium to high-throughput analysis. In this first part we focus on the analysis of the polyphenol lignin (Figure 1). The method starts of with preparing destarched cell wall material. The resulting lignocellulosics are then split up to determine its lignin content by acetylbromide solubilization(3), and its lignin composition in terms of its syringyl, guaiacyl- and p-hydroxyphenyl units(5). The protocol for analyzing the carbohydrates in lignocellulosic biomass including cellulose content and matrix polysaccharide composition is discussed in Part II(2).
工业和社会对可再生、碳中和且可持续的原材料的需求已成为21世纪最紧迫的问题之一。这重新激发了人们对将植物产品用作工业原料以生产运输用液体燃料（1）以及生物复合材料等其他产品（7）的兴趣。植物生物质仍然是地球上最大的未开发储备之一（4）。它主要由细胞壁组成，细胞壁由富含能量的聚合物构成，包括纤维素、各种半纤维素（基质多糖）以及多酚木质素（6），因此有时被称为木质纤维素。然而，植物细胞壁已进化得难以降解，因为细胞壁为细胞和整个植物提供抗张强度，抵御病原体，并使水能够在整个植物中运输；对于树木而言，可运输到地面以上100多米的高度。由于细胞壁具有多种功能，不同植物物种的细胞壁以及单个植物内不同细胞类型的细胞壁在结构上存在巨大差异（4）。因此，根据用于生物炼制的作物种类、作物品种或植物组织的不同，通过化学/酶促过程进行解聚以及随后将各种糖类发酵为液体生物燃料的加工步骤需要进行调整和优化。这一事实凸显了对植物生物质原料进行全面表征的必要性。在此，我们描述一种全面的分析方法，该方法能够测定木质纤维素的组成，并且适用于中高通量分析。在第一部分中，我们重点关注多酚木质素的分析（图1）。该方法首先制备脱淀粉细胞壁材料。然后将所得的木质纤维素进行分离，通过乙酰溴溶解法（3）测定其木质素含量，并根据其紫丁香基、愈创木基和对羟基苯基单元（5）确定其木质素组成。第二部分（2）将讨论分析木质纤维素生物质中碳水化合物（包括纤维素含量和基质多糖组成）的实验方案。
