Enhanced cellulase production in Trichoderma reesei RUT C30 via constitution of minimal transcriptional activators

Background: Cellulase can convert lignocellulosic feedstocks into fermentable sugars, which can be used for the industrial production of biofuels and chemicals. The high cost of cellulase production remains a challenge for lignocellulose breakdown. Trichoderma reesei RUT C30 serves as a well-known industrial workhorse for cellulase production. Therefore, the enhancement of cellulase production by T. reesei RUT C30 is of great importance. Results: Two sets of novel minimal transcriptional activators (DBDace2 -VP16 and DBDcre1-VP16) were designed and expressed in T reesei RUT C30. Expression of DBDace2-VP16 and DBDcre1-VP16 improved cellulase production under induction (avicel or lactose) and repression (glucose) conditions, respectively. The strain T-MTA66 under avicel and T-MT(A1)39 under glucose with the highest cellulase activities outperformed other transformants and the parental strain under the corresponding conditions. For T-MTA66 strains, the highest FPase activity was approximately 1.3-fold greater than that of the parental strain RUT C30 at 120 h of cultivation in a shake flask using avicel as the sole carbon source. The FPase activity (U/mg biomass) in T-MT(A139) strains was approximately 26.5-fold higher than that of the parental strain RUT C30 at 72 h of cultivation in a shake flask using glucose as the sole carbon source. Furthermore, the crude enzymes produced in the 7-L fermenter from T-MTA66 and T-MTA1(39) supplemented with commercial beta-glucosidase hydrolyzed pretreated corn stover effectively. Conclusions: These results show that replacing natural transcription factors with minimal transcriptional activators is a powerful strategy to enhance cellulase production in T. reesei. Our current study also offers an alternative genetic engineering strategy for the enhanced production of industrial products by other fungi.