Single Mutation in Transcriptional Activator Xyr1 Enhances Cellulase and Xylanase Production in Trichoderma reesei on Glucose

To achieve cost-effective production of lignocellulolyticenzymesfor biorefinery processes, engineering transcription factors representsa powerful strategy to boost cellulase and xylanase in Trichoderma reesei. In this study, a novel mutation(R434L) in xylanase regulator 1 (Xyr1) was identified based on theyeast one-hybrid screening system. The point mutation was locatedin the middle homology region of Xyr1 with unclear functions, indicatinga significant role for this domain in tuning Xyr1 transactivation.When constitutively expressed in T. reesei & UDelta;xyr1 (OEXR434L), Xyr1(R434L) led to highly improved production of both cellulases and xylanaseson glucose compared with a strain similarly expressing Xyr1 (OEX).The respective 0.8- and 0.7-fold increases in extracellular pNPCaseand xylanolytic activity were further verified to result from thegreatly elevated transcription of major cellulase and xylanase genesin OEXR434L. Moreover, the saccharification efficiencyof corn stover with OEXR434L enzyme cocktails was enhancedby 21% compared with that of OEX.

Automated summary

Engineering transcription factors can enhance the cost-effective production of lignocellulolytic enzymes for biorefinery processes. A novel mutation (R434L) in xylanase regulator 1 (Xyr1) was found to significantly improve cellulase and xylanase production in Trichoderma reesei. The increased transcription of major cellulase and xylanase genes in the mutant strain (OEXR434L) was verified to be responsible for the improved enzyme production.