The Influence of Trctf1 Gene Knockout by CRISPR–Cas9 on Cellulase Synthesis by Trichoderma reesei with Various Soluble Inducers

Knockout of the transcriptional repressor Trctf1 is known to enhance the yield of cellulose-induced cellulase synthesis in Trichoderma reesei. However, different inducers possess distinct induction mechanisms, and the effect of Trctf1 on cellulase synthesis with soluble inducers remains unknown. To evaluate the effect of the Trctf1 gene on cellulase synthesis and develop a high-yielding cellulase strain, we established a CRISPR–Cas9 genome editing system in T. reesei Rut C30 using codon-optimized Cas9 protein and in vitro transcribed RNA. This study demonstrated that T. reesei ΔTrctf1 with the Trctf1 gene knocked out showed no statistically significant differences in cellulase, cellobiohydrolase, endoglucanase, and β−glucosidase production when induced with MGD (the mixture of glucose and sophorose). However, when induced with lactose, the activities of these enzymes increased by 20.2%, 12.4%, and 12.9%, respectively, with no statistically significant differences in β−glucosidase activity. The hydrolysis efficiency on corn stover of cellulases produced by T. reesei ΔTrctf1 under different inducers was not significantly different from that of wild-type cellulases, indicating that Trctf1 gene deletion has little effect on the cellulase cocktail. These findings contribute to a better understanding of the molecular mechanisms underlying the regulation of T. reesei cellulase synthesis by different soluble inducers, as well as the construction of high-yield cellulase gene−engineered strains.