Reformulating the Hydrolytic Enzyme Cocktail of Trichoderma reesei by Combining XYR1 Overexpression and Elimination of Four Major Cellulases to Improve Saccharification of Corn Fiber

The industrial fungus Trichoderma reesei has an outstanding capability of secreting an enzyme cocktail comprising multiple plant biomass-degrading enzymes. Herein, the overexpression of XYR1, the master transactivator controlling (hemi)cellulase gene expression, was performed in T. reesei lacking four main cellulase-encoding genes. The resultant strain Delta 4celOExyr1 was able to produce a dramatically different profile of secretory proteins on soluble glucose or lactose compared with that of the wild-type T. reesei. The Delta 4celOExyr1 secretome included cellulases EGIII and BGLI as well as several hemicellulases and nonhydrolytic cellulose degradation-associated proteins that are not preferentially induced in the wild-type T. reesei strain. Delta 4celOExyr1 produced a significant amount of alpha-arabinofuranosidase I on lactose, and the crude enzyme cocktail of Delta 4celOExyr1 not only released a considerable quantity of glucose but also exhibited remarkable performance in the hydrolytic release of xylose, arabinose, and mannose from un-pretreated corn fiber. These results showed that the engineered T. reesei strain holds great potential for improving the saccharification efficiency of the hemicellulosic constituents within corn fiber.

Automated summary

The engineered T. reesei strain showed significant differences in secreted protein composition and enzymatic activity compared to the wild-type strain, demonstrating great potential for improving saccharification efficiency of hemicellulosic constituents within corn fiber.