Effect of earlier unfolded protein response and efficient protein disposal system on cellulase production in Rut C30

Trichoderma reesei (T. reesei) has been widely used in production of cellulolytic enzymes and heterologous proteins because of its high secretion capacity. The lack of knowledge on protein secretion mechanisms, however, still hinders rational improvement on cellulase production. The transcript levels of cellulases and components involved in post-transcriptional procedures were compared in this study between two mutants, QM9414 and Rut C30 for evaluating the effects of modification and secretion upon cellulase production. The results showed that cellulase induction by cellulose drastically up-regulated expressions of the sensor of unfolded protein, chaperone and folding-assisted enzymes in endoplasmic reticulum and resulted in unfolded protein response (UPR) and low-grade increase in secretory transporters' expression similar to that of chemical treatment. Rut C30 demonstrated earlier and more sustainable expressions of elements involved in UPR and lower amount of cellular retained cellulase compared to QM9414, indicating that Rut C30 had hypercellulolytic property partially for its earlier and enhanced UPR to more efficiently dispose of protein. Modifying post-translational peptides and enhancing protein flux to avoid protein accumulation during cellulase production may be a feasible approach for strain improvement.