裂解性多糖单加氧酶在链霉菌降解木质素中的机制研究

放线菌是土壤生态系统常见的木质纤维素分解者，在土壤凋落物的分解中发挥重要作用，但其对木质素的降解机制少见报道。广泛分布于微生物中的裂解性多糖单加氧酶（LPMOs）被认为对木质纤维素降解意义重大。申请人最近发现链霉菌LPMOs能被木质素诱导，转录水平显著上调，并与木质素降解过氧化物酶共表达，推测LPMOs在链霉菌降解木质素中发挥重要作用。本项目以Streptomyces coelicolor L10为对象，在解析其降解木质素的组学基础上，通过基因敲除等从体内研究LPMOs驱动木质素降解的功能和途径，从体外证实LPMOs驱动的木质素降解反应，并从过氧化氢产生机制揭示LPMOs参与木质素降解的分子机理，最终阐明LPMOs通过产生过氧化氢驱动过氧化物酶和芬顿反应参与链霉菌降解木质素的途径和机制。本项目拓展了LPMOs在木质素降解中的功能，并对链霉菌木质素降解和碳循环理论的完善和发展具有重要意义。

Actinomycetes are common decomposers of lignocellulosic biomass in soil ecosystems and play an important role in the decomposition of litters on soil. However, fewer reports are available on the mechanisms of lignin depolymerization by soil Actinomycetes. The recently discovered lytic polysaccharide monooxygenases (LPMOs) widely distributed in microorganisms, which are believed to be vital for the degradation of lignocellulose. Our recent studies found that LPMOs expression of Streptomyces could be induced by lignin, which caused that the transcription level was significantly up-regulated, and co-expressed with lignin-degrading peroxidase. We speculated that LPMOs played an important role in the degradation of lignin by Streptomyces. Thus, the project will focus on the LPMO-mediated mechanisms of lignin degradation by a lignin-degrading Streptomyces coelicolor L10. Firstly, we will investigate the omics profile of S. coelicolor during the degradation of lignin. Secondly, we will reveal the function and pathways of LPMOs-mediated lignin degradation in vivo by gene knockout technology, identified the LPMOs-driven lignin degradation reaction in vitro and clarify the biochemical mechanism of LPMOs generating hydrogen peroxide. Finally we will demonstrate the LPMOs of S. coelicolor involve in the lignin degradation by generating hydrogen peroxide to drive lignin-degrading peroxidase reaction and improve the fenton reaction. This project will expand the new functions of LPMOs in lignin biodegradation, and be of great significance to the improve and develop the theory of degradation and carbon cycling of lignin by Streptomyces.