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Background: Biomass-degrading enzymes with improved activity and stability can ameliorate substrate saccharification and make biorefineries economically feasible. Filamentous fungi are a rich source of carbohydrate-active enzymes (CAZymes) for biomass degradation. The newly isolated LPH172 strain of the thermophilic Ascomycete Thielavia terrestris has been shown to possess high xylanase and cellulase activities and tolerate well low pH and high temperatures. Here, we aimed to illuminate the lignocellulose degrading machinery and novel carbohydrate-active enzymes in LPH172 in detail.Results: We sequenced and analysed the 36.6-Mb genome and transcriptome of LPH172 during growth on glucose, cellulose, rice straw, and beechwood xylan. In total, 411 CAZy domains were found among 10,128 predicted genes. Compared to other fungi, auxiliary activity (AA) enzymes were particularly enriched. GC content was higher in coding sequences than in the overall genome. A high GC3 content was hypothesised to contribute to thermophilicity. T. terrestris employed mainly lytic polysaccharide monooxygenases (LPMOs) and glycoside hydrolase (GH) family 7 glucanases to attack cellulosic substrates, and conventional hemicellulases (GH10 and GH11) to degrade xylan. The observed co-expression and co-upregulation of AA9 LPMOs, other AA CAZymes, and (hemi)cellulases points to a complex and nuanced degradation strategy. Growth on more complex and heterogeneous substrates resulted in a more varied but generally lower gene expression. Conclusions: Our analysis of the genome and transcriptome of T. terrestris LPH172 elucidates the enzyme arsenal the fungus uses to degrade lignocellulosic substrates. The study provides the basis for future characterisation of potential new enzymes for industrial biomass saccharification. |
