Visualizing Lignin Coalescence and Migration Through Maize Cell Walls Following Thermochemical Pretreatment
Visualizing Lignin Coalescence and Migration Through Maize Cell Walls Following Thermochemical Pretreatment
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DOI：
10.1002/bit.21959
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发表时间：
2008-12-01
影响因子：
3.8
通讯作者：
Vinzant, Todd B.
中科院分区：
文献类型：
--
作者：
Donohoe, Bryon S.;Decker, Stephen R.;Vinzant, Todd B.
植物细胞壁主要由纤维素、半纤维素、木质素和果胶组成。在这些成分中，木质素表现出独特的化学和生理功能。虽然木质素可以用作产品原料或燃料，但木质素也通常被视为生物质的有效酶分解成糖的障碍。事实上，许多预处理策略侧重于从生物质中去除大量木质素，以更好地实现糖化。为了更好地了解稀酸预处理后留在固体中的生物质木质素的命运，我们进行了结构研究，以跟踪生物质细胞壁上和壁内的木质素。扫描电镜和透射电镜成像显示了预处理生物质细胞壁上和细胞壁内出现的一系列液滴形态；以及积聚液滴的特定超微结构区域。这些液滴通过红外光谱、核磁共振、抗体标记和细胞化学染色证明含有木质素。我们提供的证据支持这样的观点，即达到木质素相变温度范围以上的热化学预处理会导致木质素凝聚成更大的熔融体，这些熔融体可以在细胞壁内外迁移，并可以重新沉积在植物细胞壁表面。这种木质素的分解和重新定位可能至少与木质素的去除一样重要，以提高生物质对糖和燃料生产的消化率。
Plant cell walls are composed primarily of cellulose, hemicelluloses, lignins, and pectins. Of these components, lignins exhibit unique chemistry and physiological functions. Although lignins can be used as a product feedstock or as a fuel, lignins are also generally seen as a barrier to efficient enzymatic breakdown of biomass to sugars. Indeed, many pretreatment strategies focus on removing a significant fraction of lignin from biomass to better enable saccharification. In order to better understand the fate of biomass lignins that remain with the solids following dilute acid pretreatment, we undertook a structural investigation to track lignins on and in biomass cell walls. SEM and TEM imaging revealed a range of droplet morphologies that appear on and within cell walls of pretreated biomass; as well as the specific ultrastructural regions that accumulate the droplets. These droplets were shown to contain lignin by FTIR, NMR, antibody labeling, and cytochemical staining. We provide evidence supporting the idea that thermochemical pretreatments reaching temperatures above the range for lignin phase transition cause lignins to coalesce into larger molten bodies that migrate within and out of the cell wall, and can redeposit on the surface of plant cell walls. This decompartmentalization and relocalization of lignins is likely to be at least as important as lignin removal in the quest to improve the digestibility of biomass for sugars and fuels production.