Combinational manipulation of transcription factors, CreA and ClbR, is a viable strategy to improve cellulolytic enzyme production in Aspergillus aculeatus

Abstract

The production of cellulolytic enzymes in response to inducible carbon sources is mainly regulated at the transcriptional level in filamentous fungi. We have identified a cellobiose-response regulator (ClbR) controlling the expression of cellulolytic enzyme-encoding genes in Aspergillus aculeatus. However, the engineering potential of combining the deletion of transcriptional repressors with the overexpression of transcriptional activators to enhance enzyme production has not been analyzed. Here, we investigated the effect of the deletion of the transcriptional repressor creA and the overexpression of the transcriptional activator clbR in enzyme production in A. aculeatus. Here, we verified that a combination of creA deletion and clbR overexpression (Δc&OE) improved cellulase, β-1,4-xylanase, and β-glucosidase production. Cellulase and β-1,4-xylanase production increased 3.4- and 8.0-fold in Δc&OE compared with the host strain (MR12) at 96-h incubation, respectively. β-Glucosidase production in ΔcreA and Δc&OE increased approximately 5.0-fold compared with that in MR12 at 240-h incubation. Transcriptional analysis revealed that the increase in enzyme production was due to increased expression of cellobiohydrolase, endo-β-1,4-glucanase, β-1,4-xylanase, and β-glucosidase 1 (bgl1). Interestingly, bgl1 expression in ΔcreA increased in a dose-dependent manner in response to glucose. Thus, combinational manipulation of transcription factors improved cellulase, xylanase, and β-glucosidase production in A. aculeatus.