新型木质素模型物平台构建及其调控机制研究

Lignin is the second abundant and important natural plant biopolymers next to cellulose, which accounts for approximately 30% of the organic carbon in the biosphere. It is an amorphic three-dimensional substance with internal linkage of β-O-4, β-5 and 5-5, which is the phenylpropanoid polymers produced primarily from oxidative polymerization of three 4-hydroxycinnamyl alcohols differing in their degrees of methoxylation. Lignin can be converted into biofuels and chemical materials. As a highly abundant natural polymer, the biosynthesis of lignins and its chemical/mechanical properties, have attracted significant attention for decades. However, because of its complexity and heterogeneity, it has been a most challenging problem for scientists to understand the composition and structure of lignin, to some extent, which also hinders the research of high-value utilization of lignin. Lignin model compounds, which could be used as reference standard compounds, plays essential roles in the lignin structural analysis. In this study, we have synthesized a series of lignin model compound with coniferyl alcohol and ferulic acid as starting materials. The synthetic pathways and reaction mechanism were revealed based on the NMR characterization and analysis of chemical degradation analysis and GC-MS, HPLC and XRD determination. In addition, the virgin lignin structure was also investigated using 2 D NMR based on complete dissolution in DMSO/pyridine or DMSO/NMI. Moreover, the linkages between lignin and hemicelluloses were also studied.

木质素是仅次于纤维素的天然高分子化合物，由苯丙烷单元愈创木基、紫丁香基和对羟苯基主要以β-O-4, β-5和5-5等键连接的网状结构大分子，它可以转化为生物燃料及化工原料。但由于对木质素生物合成途径及其单元间键合机制仍不明确，限制了木质素高值转化及利用。本项目拟开展新型木质素模型物平台构建及其调控机制的研究。以木质素单体松柏醇及阿魏酸为起始物，模拟细胞壁生长环境并结合化学合成法，合成不同结构的木质素多聚体模型化合物。基于GC-MS、HPLC、XRD、1H-NMR，13C-NMR，2D-HSQC和2D-HMBC等分析手段解译合成模型物结构，揭示木质素多聚体的合成途径与机理，阐明其调控反应机制。利用合成的木质素模型化合物，结合全溶二维核磁分析技术，探索天然木质素大分子结构性质及键合机制，解译木质素-碳水化合物单元间连接键类型及数量，建立半纤维素与木质素键合模型，为木质素高值化利用奠定理论基础。

木质素是自然界中储量最丰富的芳香族化合物，其可转化为多种化学品及功能材料，具有重要的应用价值。但由于木质素结构复杂，其由苯丙烷单元愈创木基、紫丁香基和对羟苯基主要以β-O-4，β-5 和5-5 等键型连接的网状结构大分子，同时，木质素和半纤维素之间有着化学键连接，使得木质素的生物合成过程及其结构表征方面仍有诸多问题未能解决。本项目针对木质素研究存在的瓶颈，本着复杂问题简单化的研究思路，开展了木质素新型多聚体模型物合成及纯化研究，同时，由于木质素模型物可以更好解译反应过程及机理，对新型溶剂木质素分离、木质素模型物的抗菌及其催化转化也进行研究。此外，在细胞壁天然木质素大分子原位法分析也进行了探索。经过系统研究木质素模型物合成及其转化，实现了高效、定向合成木质素多聚体模型物，阐明木质素单体交联聚合机理，创立新型木质素多聚体模型物合成方法及路线，构建了新型木质纤维素全溶体系及分析方法；在国际和国内期刊发表论文5篇，其中SCI收录论文4篇（含1篇接收论文），1篇中文核心论文，获得教育部自然科学二等奖1项（排名第二），研究结果对木质纤维素组分结构解译及其高值转化及利用具有重要的理论意义。