Abstract
BackgroundCellulase 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.ResultsTwo 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 TMTA66 under avicel and TMTA139 under glucose with the highest cellulase activities outperformed other transformants and the parental strain under the corresponding conditions. For TMTA66 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 TMTA139 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 TMTA66 and TMTA139 supplemented with commercial β-glucosidase hydrolyzed pretreated corn stover effectively.ConclusionsThese 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.
Highlights
Cellulase can convert lignocellulosic feedstocks into fermentable sugars, which can be used for the industrial production of biofuels and chemicals
We suggest that the minimal transcriptional activators DBDace2-VP16 and D BDcre1-VP16 can enhance cellulase production
Construction of transformants with minimal transcriptional activators Each compact minimal transcription activator consists of one DNA binding domain (DBD) of the native transcription factor and the transcriptional activation domain VP16
Summary
Cellulase can convert lignocellulosic feedstocks into fermentable sugars, which can be used for the industrial production of biofuels and chemicals. Lignocellulosic feedstocks are abundant and renewable resources in nature They have been used to produce environment-friendly biofuels and chemicals, which have received increased attention for research [1]. The conversion of lignocellulosic feedstocks into fermentable sugars involving cellulase-based enzymatic saccharification is the key issue in large-scale production of biofuels and chemicals [2]. The cellulase produced in T. reesei RUT C30 mainly comprise two cellobiohydrolases (CBHI and CBHII), two endoglucanases (EGI and EGII), and β-glucosidase I (BGLI) that synergistically hydrolyze lignocellulosic materials, together with related xylanases and auxiliary. EGI and EGII are the two main endoglucanases and together account for 6–20% of the total produced proteins [11]. Swollen in, as a non-enzymatic cellulose attacking enzyme, and lytic polysaccharide monooxygenases (LPMOs) synergistically degrade lignocellulosic materials as auxiliary proteins [14, 15]
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