Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, P.O. Box 1052, E-41080 Seville, Spain.
J Agric Food Chem. 2015 Jan 21;63(2):603-13. doi: 10.1021/jf505808c. Epub 2015 Jan 7.
The structure of the lignin from brewer's spent grain (BSG) has been studied in detail. Three different lignin preparations, the so-called "milled-wood" lignin (MWL), dioxane lignin (DL), and cellulolytic lignin (CEL), were isolated from BSG and then thoroughly characterized by pyrolysis GC/MS, 2D-NMR, and derivatization followed by reductive cleavage (DFRC). The data indicated that BSG lignin presents a predominance of guaiacyl units (syringyl/guaiacyl ratio of 0.4-0.5) with significant amounts of associated p-coumarates and ferulates. The flavone tricin was also present in the lignin from BSG, as also occurred in other grasses. 2D-NMR (HSQC) revealed that the main substructures present are β-O-4' alkyl-aryl ethers (77-79%) followed by β-5' phenylcoumarans (11-13%) and lower amounts of β-β' resinols (5-6%) and 5-5' dibenzodioxocins (3-5%). The results from 2D-NMR (HMBC) and DFRC indicated that p-coumarates are acylating the γ-carbon of lignin side chains and are mostly involved in condensed structures. DFRC analyses also indicated a minor degree of γ-acylation with acetate groups, which takes place preferentially on S lignin (6% of S units are acetylated) over G lignin (only 1% of G units are acetylated).
从啤酒糟（BSG）中详细研究了木质素的结构。从 BSG 中分离出三种不同的木质素制剂，即所谓的“磨木”木质素（MWL）、二氧杂环己烷木质素（DL）和纤维素木质素（CEL），并通过热解 GC/MS、2D-NMR 和衍生化后还原裂解（DFRC）进行了彻底表征。数据表明，BSG 木质素呈现出愈创木基单元（syringyl/guaiacyl 比为 0.4-0.5）的优势，并且存在大量相关的对香豆酸酯和阿魏酸酯。黄酮木犀草素也存在于 BSG 木质素中，这也发生在其他草类中。2D-NMR（HSQC）揭示了存在的主要亚结构是β-O-4'烷芳基醚（77-79%），其次是β-5'苯基香豆烷（11-13%）和较低含量的β-β'树脂醇（5-6%）和 5-5'二苯并二氧杂环辛烷（3-5%）。来自 2D-NMR（HMBC）和 DFRC 的结果表明，对香豆酸酯酰化木质素侧链的γ-碳，并且主要参与缩合结构。DFRC 分析还表明，与乙酸酯基的γ-酰化程度较小，主要发生在 S 木质素（6%的 S 单元乙酰化）上，而不是 G 木质素（只有 1%的 G 单元乙酰化）。
