Development of a novel expression platform for heterologous protein production via deleting the p53-like regulator...

Trichoderma reesei is widely used as a protein production host due to its high natural capacity to secrete enzymes. Nonetheless, the complexity and abundance of secretome limit its extensive application in heterologous protein production. Here, a novel heterologous protein expression system with remarkable reduction of undesired background proteins was developed by deletion of the p53-like transcriptional factor Vib1. The vib1-deletion strain (Δvib1) exhibited a dramatic decrease in cellulase and protease secretion, whereas the growth of Δvib1 was comparable to that of the parental strain QM53, indicating that Δvib1 possesses a great potential for heterologous protein production. Therefore, the Aspergillus niger β-glucosidase-coding gene bglA was expressed in Δvib1 and QM53 to demonstrate the feasibility of Δvib1 as the protein production host. The bglA-expression strains QVB-1 (Δvib1:bglA) and Q53B-1 (QM53:bglA) produced approximately 17.2 IU/mg and 14.7 IU/mg of β-glucosidase activity, respectively. In addition, the β-glucosidase activity in the supernatant of QVB-1 remained constant after 4-week incubation whereas that of Q53B-1 decreased by more than 60%. Furthermore, transcription levels of the genes involved in the unfolded protein response were relatively decreased in Δvib1 compared with that in QM53, indicating the increased protein folding capacity of the endoplasmic reticulum in Δvib1. These results demonstrate the feasibility of using T. reesei Δvib1 as the host for heterologous protein production.