Shao Qi, Li Xin, Chen Ying, Zhang Zhijun, Cui Yong, Fan Huan, Wei Dongsheng
Department of Microbiology, College of Life Sciences, Nankai University, Tianjin, China.
Institute of Agro-Products Preservation and Processing Technology, Tianjin Academy of Agricultural Sciences, Tianjin, China.
Front Microbiol. 2022 Jul 11;13:935462. doi: 10.3389/fmicb.2022.935462. eCollection 2022.
The degradation of lignocellulose by fungi, especially white-rot fungi, contributes a lot to carbon cycle, bio-fuel production, and many other bio-based applications. However, the existing enzymatic and non-enzymatic degradation mechanisms cannot be unequivocally supported by simulation experiment, meaning that additional mechanisms might exist. Right now, it is still very difficult to discover new mechanisms with traditional forward genetic approaches. To disclose novel lignin degradation mechanisms in white-rot fungi, a series of fusants from wide cross by protoplast fusion between , a well-known lignin-degrading fungus, and , a well-known model organism unable to degrade lignocellulose, was investigated regarding their abilities to degrade lignin. By analyzing the activity of traditional lignin-degrading enzyme, the ability to utilize pure lignin compounds and degrade corn stalk, a fusant D1-P was screened out and proved not to contain well-recognized lignin-degrading enzyme genes by whole-genome sequencing. Further investigation with two-dimension nuclear magnetic resonance (NMR) shows that D1-P was found to be able to degrade the main lignin structure β-O-4 linkage, leading to reduced level of this structure like that of the wild-type strain after a 30-day semi-solid fermentation. It was also found that D1-P shows a degradation preference to β-O-4 linkage in A(S)-. Therefore, wide cross between white-rot fungi and provides a powerful tool to uncover novel lignocellulose degradation mechanism that will contribute to green utilization of lignocellulose to produce bio-fuel and related bio-based refinery.
真菌，尤其是白腐真菌对木质纤维素的降解，对碳循环、生物燃料生产以及许多其他生物基应用都有很大贡献。然而，现有的酶促和非酶促降解机制无法得到模拟实验的确切支持，这意味着可能存在其他机制。目前，用传统的正向遗传学方法发现新机制仍然非常困难。为了揭示白腐真菌中新型木质素降解机制，研究了一系列通过原生质体融合产生的远缘杂种融合体，这些融合体由一种著名的木质素降解真菌与一种不能降解木质纤维素的著名模式生物融合而成，并考察了它们降解木质素的能力。通过分析传统木质素降解酶的活性、利用纯木质素化合物的能力以及降解玉米秸秆的能力，筛选出了一个融合体D1-P，通过全基因组测序证明其不含有公认的木质素降解酶基因。二维核磁共振（NMR）进一步研究表明，在30天的半固体发酵后，发现D1-P能够降解主要的木质素结构β-O-4键，导致该结构的水平降低，与野生型菌株相似。还发现D1-P对A(S)中的β-O-4键表现出降解偏好。因此，白腐真菌与[未提及的生物]之间的远缘杂交为揭示新型木质纤维素降解机制提供了有力工具，这将有助于木质纤维素的绿色利用，以生产生物燃料和相关的生物基精炼产品。
