Lignocellulose is the most abundant and renewable biomass resource on the planet. Lignocellulose can be converted into biofuels and high-value compounds; however, its recalcitrance makes its breakdown a challenge. Lytic polysaccharide monooxygenases (LPMOs) offer tremendous promise for the degradation of recalcitrant polysaccharides. Chaetomium thermophilum, having many LPMO-coding genes, is a dominant thermophilic fungus in cellulose-rich and self-heating habitats. This study explores the genome, secretomes and transcript levels of specific genes of C. thermophilum. The genome of C. thermophilum encoded a comprehensive set of cellulose- and xylan-degrading enzymes, especially 18 AA9 LPMOs that belonged to different subfamilies. Extracellular secretomes showed that arabinose and microcrystalline cellulose (MCC) could specifically induce the secretion of carbohydrate-active enzymes (CAZymes), especially AA9 LPMOs, by C. thermophilum under different carbon sources. Temporal analyses of secretomes and transcripts revealed that arabinose induced the secretion of xylanases by C. thermophilum, which was obviously different from other common filamentous fungi. MCC could efficiently induce the specific secretion of LPMO2s, possibly because the insert in loop3 on the substrate-binding surface of LPMO2s strengthened its binding capacity to cellulose. LPMO2s, cellobio hydrolases (CBHs) and cellobiose dehydrogenases (CDHs) were cosecreted, forming an efficient cellulose degradation system of oxidases and hydrolases under thermophilic conditions. The specific expression of LPMO2s and cosecretion of hydrolases and oxidases by the thermophilic fungus C. thermophilum play an important role in cellulose degradation. This insight increases our understanding of the cellulose degradation under thermophilic conditions and may inspire the design of the optimal enzyme cocktails for more efficient exploration of biomass resources in industrial applications.

中文翻译：

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基于综合功能组学的嗜热真菌Chaetomium thermophilum的纤维素降解机制研究。

木质纤维素是地球上最丰富和可再生的生物质资源。木质纤维素可以转化为生物燃料和高价值化合物；然而，它的顽固性使其崩溃成为一个挑战。裂解多糖单加氧酶 (LPMO) 为顽固多糖的降解提供了巨大的前景。Chaetomium thermophilum 具有许多 LPMO 编码基因，是富含纤维素和自热栖息地的主要嗜热真菌。本研究探讨了嗜热梭菌特定基因的基因组、分泌组和转录水平。C. thermophilum 的基因组编码了一套全面的纤维素和木聚糖降解酶，尤其是属于不同亚科的 18 个 AA9 LPMO。细胞外分泌组显示阿拉伯糖和微晶纤维素（MCC）可以特异性诱导不同碳源下嗜热梭菌分泌碳水化合物活性酶（CAZymes），尤其是AA9 LPMO。对分泌组和转录本的时间分析表明，阿拉伯糖诱导嗜热梭菌分泌木聚糖酶，这与其他常见的丝状真菌明显不同。MCC可以有效诱导LPMO2s的特异性分泌，可能是因为LPMO2s底物结合表面loop3中的插入增强了其与纤维素的结合能力。LPMO2s、纤维二糖水解酶 (CBHs) 和纤维二糖脱氢酶 (CDHs) 共同分泌，在嗜热条件下形成了一个有效的氧化酶和水解酶纤维素降解系统。嗜热真菌嗜热真菌 C. thermophilum 对 LPMO2s 的特异性表达以及水解酶和氧化酶的共分泌在纤维素降解中起重要作用。这一见解增加了我们对嗜热条件下纤维素降解的理解，并可能激发最佳酶混合物的设计，以更有效地探索工业应用中的生物质资源。