Biologia de sistemas do fungo Trametes villosa CCMB561: integração de análises ômicas para compreensão do metabolismo da lignocelulose

Abstract

The bioconversion of lignocellulosic materials, a renewable and sustainable raw material, is an efficient alternative to produce biofuels and obtain chemicals. These residues consist mostly of cellulose, hemicellulose, and lignin. For the use of all the lignocellulosic constituents, both delignification and saccharification of biomass are needed for the removal/modification of lignin and subsequent depolymerization of polymeric carbohydrates to simple sugars. White- rot fungi are organisms that, by the production of hydrolytic and oxidative enzymes, have the ability to degrade all the polymers of the plant cell wall. Previous studies using Trametes villosa CCMB561 demonstrated the potential of this isolate to produce ligninolytic enzymes, and thus act in the depolymerization of plant residues. Hence, in order to reveal the genetic bases of lignocellulose degradation by the fungus Trametes villosa CCMB561, its genome was sequenced using two sequencing platforms (MinION and Illumina) and assembled using different software. After the assembly, the genome had coding regions, tRNAs, transposable elements, Secondary Metabolite Gene Clusters (SMGCs) and Carbohydrate-Active Enzymes (CAZymes) encoding genes annotated. In addition, biochemical assays for enzymatic quantification, as well as, gene expression analyses by qPCR and transcriptome sequencing were carried out. Through the analyses, a genome with 46,748,415 bp, 99.1% of completeness, and 14,540 genes were obtained. A total of 426 genes encoding CAZymes and 22 SMGCs were identified. The results of biochemical assays and gene expression analyses revealed that T. villosa CCMB561 has the ability to grow in culture medium with lignin as the sole carbon source. In this substrate, an overexpression of Cytochrome P450 was detected, which was associated with the initial process of O-demethylation of lignin for subsequent depolymerization by oxidases and peroxidases. Clusters of up-regulated CAZymes-encoding genes were identified in lignin and sugarcane bagasse, revealing that T. villosa CCMB561 acts in the simultaneous depolymerization of lignin, cellulose, hemicellulose, and pectin. Furthermore, genes encoding nitroreductases and homogentisate-1,2-dioxygenase that act in the degradation of organic pollutants were up-regulated in the lignin medium. Finally, these findings revealed the genetic mechanisms of lignocellulose breakdown by Trametes villosa CCMB561 and exhibits the great potential of this fungal isolate to be used for the production of enzymes with biotechnological interest and application in the conversion of lignocellulosic biomass and degradation of organic pollutants.