同位素标记法用于植物纤维中LCC蒸煮过程中结构变化的研究

为了研究植物纤维原料中的木素-碳水化合物复合体(lignin-carbohydrate complexes,LCCs)在硫酸盐法蒸煮过程中的结构变化,向天然植物稻秆中投入带¹³C同位素标记的松柏醇葡萄糖苷,用Björkman的方法将木素-碳水化合物复合体从稻秆粉末中分离出来,结合红外光谱和高分辨率的液态¹³C NMR检测分析发现木素与糖类主要是通过苯甲醚键、酯键和缩醛键连接。其中,在LCC中木素的主要结构为β-O-4结构。将分离出来的带标记的LCC模拟硫酸盐法蒸煮,分离得到木素-碳水化合物复合体的硫酸盐木素。通过对天然稻秆LCC硫酸盐木素和稻秆LCC硫酸盐木素-α-¹³C]的红外光谱和高分辨率¹³C NMR分析,证实了在稻秆LCC硫酸盐蒸煮后,产物中还存在少量以苯甲醚键和缩醛键连接的LC结构。另外,所得硫酸盐木素主要以β-O-4结构为主,含有少量的β-β、β-5和β-1结构。

Tracking structural change of LCC in plant by isotopic tracer technique

To understand structure change of lignin-carbohydrate complexes (LCCs) in kraft cooking process,it was separated firstly out from the powder of rise straw by Björkman procedure,into which coniferyl alcohol glucoside with ¹³C-label had been rejected,and its structure was determined by ¹³C NMR and FT-IR spectra.The result showed that lignin was linked to carbohydrate by benzyl ether,ester and α-ketal bonds,and β-O-4 structure was the main structure of lignin in LCC.Then,the LCC obtained with and without ¹³C-label was cooked by kraft method and isolated respectively,to get lignin-carbohydrate complex-kraft lignins(LCC-KLs).The LCC-KLs structures were determined by ¹³C NMR and FT-IR spectra,and the intensities of α-carbons increased markedly for the sample with α-¹³C-label.The result showed that most of benzyl ether bonds and ketal linkage between lignin and carbohydrate were broken in pulping,but there still were bits of ketal linkage.Main structures of LCC-KL were found to be β-O-4 units,with a small number of phenylcoumaran units,pinoresinol units and β-1 units.