Cell Wall Degrading Enzymes in Trichoderma asperellum Grown on Wheat Bran

Abstract

Trichoderma asperellum is a filamentous fungus that is able to produce and secrete a wide range of extracellular hydrolytic enzymes used for plant cell wall degradation. The Trichoderma genus has attracted considerable attention from the biorefinery industry due to the production of cell wall degrading enzymes and strong secretion ability of this genus. Here we report extensive transcriptome analysis of plant cell wall degrading enzymes in T. asperellum. The production of cell wall degrading enzymes by T. asperellum was tested on a range of cellulosic materials under various conditions. When T. asperellum was grown on wheat bran, the greatest range of enzymes activity was detected and a total of 175 glycoside hydrolases from 48 glycoside hydrolase families were identified in the transcriptome. The glycoside hydrolases were identified on a functional level using the bioinformatical tool Peptide Pattern Recognition enabling an efficient enzyme discovery. This was furthermore used to re-annotate CAZymes present in five publically available Trichoderma species, hereby elucidating differences in CAZymes on a functional level in contrary to glycoside hydrolase family level. This comparison supports the theory that the glycoside hydrolases have evolved from a common ancestor, followed by a specialization in which saprotrophic fungi such as T. reesei and T. longibrachiatum lost a significant number of genes including several glycoside hydrolases.