Trichoderma reesei as an expression system for homologous production of individual cellulases

Official URL: http://192.168.1.20/record=b1304385 (Table of Contents)

Cellulases are a group of enzymes that can synergistically catalyze hydrolysis of cellulose into glucose, which is an essential process for conversion of huge amounts of dormant cellulosic biomass into fermentable sugar, one of the most potent alternative energy sources of the new world. Since purification is difficult and time-consuming, production of cellulases individually is more favorable for these applications that may require specific combination of different enzyme components. In order to evaluate the filamentous fungus Trichoderma reesei as an expression system for production of individual cellulases, Endoglucanase I (EG1/Cel7B), Endoglucanase III (EG3/Cel12A) and Cellobiohydrolase I (CBH1/Cel7A) were homologously expressed in the cellulase-negative mutant strain delta-xyr1 using two alternative promoters (tef1 and cdna1) on glucose medium. In this thesis we show that individual cellulase components (EG1, EG3 and CBH1) could be successfully overexpressed in active form in a cellulase negative T.reesei background under noninducing conditions for the first time in the literature. We also show that cdna1 promoter resulted in higher expression levels of EG1 and EG3. Additionally, T.reesei was established and partially optimized as an expression system which can be employed for future applications.