Molecular Changes in Corn Stover Lignin Resulting from Pretreatment Chemistry
Molecular Changes in Corn Stover Lignin Resulting from Pretreatment Chemistry
复制标题
预处理化学引起的玉米秸秆木质素的分子变化
DOI：
10.15376/biores.12.3.6262-6275
复制
发表时间：
2017-01-01
期刊：
影响因子：
1.5
通讯作者：
Lucia, Lucian
中科院分区：
文献类型：
--
作者：
Min, Douyong;Wang, Shuang-fei;Lucia, Lucian
木质素是限制多糖酶促转化为可发酵糖的无定形聚合物。因此，可以提高碳水化合物的可及性的预处理是成功的生物燃料转化方案的关键步骤。在这项研究中，玉米秸秆被分级为茎，穗轴和叶，因为它们的木质素是不同的。为了阐明木质素的变化，自水解，稀酸和碱预处理施加在样品上，然后由纤维素分解酶木质素制剂的分离。采用碱性硝基苯氧化、13 C-核磁共振（NMR）和1H-13 C杂原子单量子相干NMR分析了木质素的变化。结果表明，玉米秸秆木质素是一种含有对香豆酸酯和阿魏酸酯的对羟基苯基-愈创木基-辛基型木质素。β-芳基-醚是最丰富的单元间键，其次是缩合键，例如皮诺-/阿宾树脂酚、苯基香豆素和螺二烯酮。对于未经预处理的样品，叶木质素比茎木质素和穗轴木质素更凝聚。碱预处理去除了更多的木质素，这是由于更多的β-芳基醚键断裂。作为比较，通过酸性预处理产生更多的缩合键。愈创木基/愈创木基比率的降低表明残余木质素变得更加浓缩，并且证实在预处理期间愈创木基和对羟基苯基单元比愈创木基单元更稳定。
Lignin is an amorphous polymer that limits the enzymatic conversion of polysaccharides to fermentable sugars. Thus, a pretreatment that can enhance the accessibility of carbohydrates is a key step of successful biofuel conversion schemes. In this study, corn stover was fractioned into stem, cob, and leaf because their lignin is different. To elucidate the lignin changes, autohydrolysis, diluted acid, and alkali pretreatments were applied on the samples, followed by the isolation of cellulolytic enzyme lignin preparations. Alkaline nitrobenzene oxidation, 13C-Nuclear Magnetic Resonance (NMR), and 1H-13C heteronuclear single quantum coherence NMR were used to profile the lignin changes. The results indicated that corn stover lignin is a p-hydroxyphenyl-guaiacyl-syringyl-type lignin that incorporates p-coumarate and ferulate esters. The β-aryl-ether was the most abundant inter-unit linkage, followed by condensed linkages, e.g. pino-/syringaresinol, phenylcoumaran, and spirodienone. As for the non-pretreated samples, leaf lignin was more condensed than stem lignin and cob lignin. More lignin was removed by the alkali pretreatment due to more cleavage of β-aryl-ether linkages. As a comparison, more condensed linkages were generated by the acidic pretreatments. The decrease of the syringyl/guaiacyl ratio indicated that the residual lignin became more condensed and confirmed that guaiacyl and p-hydroxyphenyl units were more stable than syringyl units during the pretreatment.