Lin Kuan-Ting, Wang Chenxi, Guo Mond F, Aprà Edoardo, Ma Ruoshui, Ragauskas Arthur J, Zhang Xiao
Voiland School of Chemical Engineering & Bioengineering, Washington State University, Richland, WA 99354.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99352.
Proc Natl Acad Sci U S A. 2023 Aug 8;120(32):e2307323120. doi: 10.1073/pnas.2307323120. Epub 2023 Jul 31.
The complex and heterogeneous nature of the lignin macromolecule has presented a lasting barrier to its utilization. To achieve high lignin yield, the technical lignin extraction process usually severely modifies and condenses the native structure of lignin, which is a critical drawback for its utilization in conversion processes. In addition, there is no method capable of separating lignin from plant biomass with controlled structural properties. Here, we developed an N-heterocycle-based deep eutectic solvent formed between lactic acid and pyrazole (La-Py DES) with a binary hydrogen bonding functionality resulting in a high affinity toward lignin. Up to 93.7% of lignin was extracted from wheat straw biomass at varying conditions from 90 °C to 145 °C. Through careful selection of treatment conditions as well as lactic acid to pyrazole ratios, lignin with controlled levels of ether linkage content, hydroxyl group content, and average molecular weight can be generated. Under mild extraction conditions (90 °C to 120 °C), light-colored native-like lignin can be produced with up to 80% yield, whereas ether linkage-free lignin with low polydispersity can be obtained at 145 °C. Overall, this study offers a new strategy for native lignin extraction and generating lignin with controlled structural properties.
木质素大分子的复杂性和异质性一直是其利用的持久障碍。为了实现高木质素产量，工业木质素提取过程通常会严重改变和缩合木质素的天然结构，这是其在转化过程中利用的一个关键缺点。此外，目前还没有一种方法能够从植物生物质中分离出具有可控结构性质的木质素。在此，我们开发了一种基于N-杂环的深共熔溶剂，由乳酸和吡唑形成（La-Py DES），具有二元氢键功能，对木质素具有高亲和力。在90℃至145℃的不同条件下，从小麦秸秆生物质中提取的木质素高达93.7%。通过仔细选择处理条件以及乳酸与吡唑的比例，可以生成具有可控醚键含量、羟基含量和平均分子量的木质素。在温和的提取条件下（90℃至120℃），可以生产出浅色的类天然木质素，产率高达80%，而在145℃时可以获得低多分散性的无醚键木质素。总体而言，本研究为天然木质素提取和生成具有可控结构性质的木质素提供了一种新策略。
