来自转基因柳枝稷和木质素-果胶复合物模型研究的木质素-碳水化合物复合物的证据,ACS Sustainable Chemistry & Engineering

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来自转基因柳枝稷和木质素-果胶复合物模型研究的木质素-碳水化合物复合物的证据
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2023-10-23 , DOI: 10.1021/acssuschemeng.3c04322
Riddhi S. Shah _{1,

2} , Manjula Senanayake ₂ , Hong-Hai Zhang ₃ , Yunqiao Pu ₄ , Ajaya K. Biswal ₅ , Sai Venkatesh Pingali ₂ , Brian Davison ₄ , Hugh O’Neill ₂

Affiliation

木质素-碳水化合物复合物（LCC）是通过木质素与植物细胞壁多糖的相互作用形成的，被认为是生物质顽抗性的重要来源。在这项工作中，我们研究了木质素和果胶同型半乳糖醛酸 (HG) 之间形成的 LCC。使用小角中子散射 (SANS) 将热水预处理后 HG 缺陷转基因柳枝稷 ( GAUT4 -knockdown , GAUT4 -KD )的结构变化与野生型植物进行比较，结果表明，木质素聚集体增加了约 2.2 倍与野生型相比，GAUT4 -KD 生物量。这表明果胶减少导致更多的木质素重新分布，并表明木质素和 HG 之间的相互作用限制了植物细胞壁中木质素的流动性。为了更好地了解木质素和果胶之间的相互作用类型，通过在 HG 存在下聚合质子化或部分氘化的松柏醇形成脱氢聚合物 (DHP) 来制备模型复合材料。小角 X 射线散射 (SAXS) 显示 DHP 和 HG 形成高度互连的网络结构，这种结构在单个聚合物的物理混合物中是观察不到的。对比匹配 SANS 揭示了复合材料中 DHP 和 HG 的结构，并表明 HG 形成了一个膨胀的互连聚合物网络（幂律指数，P = 1.5），散布着 DHP 颗粒（回转半径，R _g，264 Å），由溶剂可及的 DHP 聚合物组成 ( P = 2.3)。傅里叶变换红外光谱显示 DHP/HG 复合材料具有独特的酯吸收带。固态核磁共振 (NMR) 分析也支持 DHP 和 HG 之间的相互作用。总的来说，这项研究为细胞壁合成过程中初级和次级细胞壁聚合物之间的关系以及果胶和木质素之间形成的LCC如何代表以前未被认识的生物质顽抗性来源提供了新的见解。这些知识可能有助于开发调节细胞壁特性的新方法，以改善生物燃料和生物产品的生产。

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Evidence for Lignin–Carbohydrate Complexes from Studies of Transgenic Switchgrass and a Model Lignin–Pectin Composite

Lignin–carbohydrate complexes (LCCs) form through interactions of lignin with plant cell wall polysaccharides and are thought to be a significant source of biomass recalcitrance. In this work, we investigated LCCs formed between lignin and pectin homogalacturonan (HG). The structural changes in HG deficient transgenic switchgrass (GAUT4-knockdown, GAUT4-KD) after hot water pretreatment were compared to wild-type plants using small-angle neutron scattering (SANS), which showed that there were ∼2.2-fold more lignin aggregates in GAUT4-KD biomass compared to the wild type. This demonstrated that decreased pectin resulted in more lignin redistribution and suggested that interactions between lignin and HG restrict lignin mobility in plant cell walls. To better understand the types of interactions between lignin and pectin, a model composite was prepared by polymerizing either protiated or partially deuterated coniferyl alcohol to form a dehydrogenation polymer (DHP) in the presence of HG. Small-angle X-ray scattering (SAXS) showed that the DHP and HG form a highly interconnected network structure that is not observed in a physical mixture of the individual polymers. Contrast matching SANS revealed the structure of DHP and HG in the composite and showed that the HG forms a swollen interconnected polymer network (power-law exponent, P = 1.5) interspersed with DHP particles (radius of gyration, R_g, 264 Å) that are composed of solvent-accessible DHP polymers (P = 2.3). Fourier transform infrared spectroscopy showed a unique ester absorption band in the DHP/HG composites. Solid-state nuclear magnetic resonance (NMR) analysis also supports interactions between DHP and HG. Overall, this study provides new insights into the relationship between primary and secondary cell wall polymers during cell wall synthesis and how LCCs formed between pectin and lignin could represent a previously unrecognized source of biomass recalcitrance. This knowledge may help develop new approaches to modulate cell wall properties to improve biofuel and bioproduct production.

更新日期：2023-10-23

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