Improved Production of Majority Cellulases in Trichoderma reesei by Integration of cbh1 Gene From Chaetomium thermophilum

Lignocellulose is an abundant waste resource and has been considered as a promising material for production of biofuels or other valuable bio-products. Currently, one of the major bottlenecks in the economic utilization of lignocellulosic materials is the cost-efficiency of converting lignocellulose into soluble sugars for fermentation. One way to address this problem is to seek superior lignocellulose degradation enzymes or further improve current production yields of lignocellulases. In the present study, the lignocellulose degradation capacity of a thermophilic fungusChaetomium thermophilumwas firstly evaluated and compared to that of the biotechnological workhorseTrichoderma reesei.The data demonstrated that compared toT. reesei, C. thermophilumdisplayed substantially higher cellulose-utilizing efficiency with relatively lower production of cellulases, indicating that better cellulases might exist inC. thermophilum. Comparison of the protein secretome betweenC. thermophilumandT. reeseishowed that the secreted protein categories were quite different in these two species. In addition, to prove that cellulases inC. thermophilumhad better enzymatic properties, the major cellulase cellobiohydrolase I (CBH1) fromC. thermophilumandT. reeseiwere firstly characterized, respectively. The data showed that the specific activity ofC. thermophilumCBH1 was about 4.5-fold higher thanT. reeseiCBH1 in a wide range of temperatures and pH. To explore whether increasing CBH1 activity inT. reeseicould contribute to improving the overall cellulose-utilizing efficiency ofT. reesei,T. reesei cbh1gene was replaced withC. thermophilum cbh1gene by integration ofC. thermophilum cbh1gene intoT. reesei cbh1gene locus. The data surprisingly showed that this gene replacement not only increased the cellobiohydrolase activities by around 4.1-fold, but also resulted in stronger induction of other cellulases genes, which caused the filter paper activities, Azo-CMC activities and beta-glucosidase activities increased by about 2.2, 1.9, and 2.3-fold, respectively. The study here not only provided new resources of superior cellulases genes and new strategy to improve the cellulase production inT. reesei, but also contribute to opening the path for fundamental research onC. thermophilum.