Laccase-mediator systems (LMS) are potential green tools to improve the valorization of lignocellulosic biomass by selective degradation of lignin. Despite extensive attention devoted to lignin degradation by LMS in literature, knowledge on the underlying mechanisms is largely limited to model compound studies. Here, we report a mechanistic study on the delignification of wheat straw (WS) and corn stover (CS) by a laccase/HBT system. Quantitative ¹³C-IS py-GC-MS analysis revealed that WS and CS were delignified in the range of 28–51% (w/w). Based on a combination of py-GC-MS, 2D NMR, SEC and RP-UHPLC-MS, extensive structural characterization of both residual and solubilized lignin structures was performed, from which we reconstructed the degradation pathway of native lignin by laccase/HBT. For the first time, we show that degradation of native lignin in the plant cell wall matrix by LMS occurs via both C_α–C_β cleavage and ether cleavage of β-O-4′ aryl ethers, and that the latter primarily occurs via cleavage of the β-O bond. C_γ-Coumaroylated substructures were found to be more recalcitrant towards degradation than non-acylated substructures. In addition to lignin degradation, our results provide evidence for grafting of HBT onto lignin.

中文翻译：

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在分子水平上理解漆酶/ HBT催化的草脱木质素

漆酶介体系统（LMS）是潜在的绿色工具，可通过选择性降解木质素来改善木质纤维素生物质的价值。尽管在文献中对LMS降解木质素的研究引起了广泛关注，但有关潜在机理的知识在很大程度上限于模型化合物研究。在这里，我们报告了通过漆酶/ HBT系统对麦草（WS）和玉米秸秆（CS）脱木质素的机理研究。定量¹³C-IS py-GC-MS分析表明，WS和CS在28-51％（w / w）范围内被脱木质素。基于py-GC-MS，2D NMR，SEC和RP-UHPLC-MS的组合，对残留的木质素结构和可溶解的木质素结构进行了广泛的结构表征，由此我们重建了漆酶/ HBT降解天然木质素的途径。对于第一次，我们显示通过LMS植物细胞壁基质天然木质素的降解发生经由两个Ç _α -C _β裂解和醚的裂解β- ö -4'芳基醚，而后者主要发生通过切割β- O键的基团。ç _γ发现共香豆酰化的亚结构比非酰化的亚结构更难以降解。除了降解木质素外，我们的结果还提供了将HBT嫁接到木质素上的证据。