Differences in the chemical structure of the lignins from sugarcane bagasse and straw
Differences in the chemical structure of the lignins from sugarcane bagasse and straw
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DOI：
10.1016/j.biombioe.2015.07.006
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发表时间：
2015-10-01
影响因子：
6
通讯作者：
Rencoret, Jorge
中科院分区：
文献类型：
--
作者：
del Rio, Jose C.;Lino, Alessandro G.;Rencoret, Jorge
甘蔗工业产生两种主要残渣，即榨汁后的纤维部分（甘蔗渣）和收获残渣（稻草）。采用热解-气相色谱-质谱联用（Py-GC/MS）、核磁共振（NMR）和衍生化还原裂解（DFRC）等方法对木质素的结构进行了研究。然而，来自甘蔗渣的木质素具有2：38：60的富含愈创木基的对羟基苯基：愈创木基：顺丁烯二酰（H：G：S）摩尔组成，来自稻草的木质素是富含愈创木基的（H：G：S为4：68：28）。组成的差异也反映在不同的单元间的联系的相对丰度。甘蔗渣木质素主要是0 -O-4'烷基-芳基醚亚结构（占NMR可测量键的83%），其次是少量的3-5'（苯基香豆素，6%）和其它缩合亚结构。来自稻草的木质素具有较低水平的β-醚（75%），但苯基香豆素（0- 5 '，15%）和二苯并二氧杂环辛（5-5/4-O-β，3%）的相对水平较高，与富含G-单元的木质素一致。两种木质素在木质素侧链的γ-羟基处被广泛酰化（在甘蔗渣和稻草中为42%和36%酰化），主要是用对香豆酸酯（优选在S-单元上），但也用乙酸酯（优选在G单元上）在较小程度上。四氢呋喃结构诊断所产生的β-β-耦合（脱氢二聚）的芥子对香豆酸酯或其交叉耦合芥子醇中发现的两种木质素，表明芥子对香豆酸酯作为一个单体参与木质化。在甘蔗的木质素中也发现了黄酮麦黄酮，这也发生在其他草中。(C)2015爱思唯尔有限公司版权所有。
Two major residues are produced by the sugarcane industry, the fibrous fraction following juice extraction (bagasse), and the harvest residue (straw). The structures of the lignins from these residues were studied by pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS), nuclear magnetic resonante (NMR), and derivatization followed by reductive cleavage (DFRC). Whereas the lignin from bagasse has a syringyl-rich p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) molar composition of 2:38:60, the lignin from straw is guaiacyl-rich (H:G:S of 4:68:28). The compositional differences were also reflected in the relative abundances of the different interunit linkages. Bagasse lignin was primarily 0 -O-4' alkyl-aryl ether substructures (representing 83% of NMR-measurable linkages), followed by minor amounts of 3-5' (phenylcoumarans, 6%) and other condensed substructures. The lignin from straw has lower levels of beta-ethers (75%) but higher relative levels of phenylcoumarans (0-5', 15%) and dibenzodioxocins (5-5/4-O-beta, 3%), consistent with a lignin enriched in G-units. Both lignins are extensively acylated at the gamma-hydroxyl of the lignin side-chain (42% and 36% acylation in bagasse and straw), predominantly with p-coumarates (preferentially on S-units) but also with acetates (preferentially on Gunits) to a minor extent. Tetrahydrofuran structures diagnostically arising from beta-beta-coupling (dehydrodimerization) of sinapyl p-coumarate or its cross-coupling with sinapyl alcohol were found in both lignins, indicating that sinapyl p-coumarate acts as a monomer participating in lignification. The flavone tricin was also found in the lignins from sugarcane, as also occurs in other grasses. (C) 2015 Elsevier Ltd. All rights reserved.