Co-feeding strategy alleviates hypoxic stress in large-scale bioreactor for optimal production of secretory recombinant proteins in Pichia pastoris

The loss of mixing efficiency inherent to bioreactor process operated at large-scale yields to the formation of concentration gradient and thus to heterogeneous culture conditions. For processes operated with methanol feeding, P. pastoris faces oscillatory culture conditions that significantly affect the cell ability to produce secretory recombinant proteins at high yield. Extended cell residence time in microenvironments of high methanol concentration and low oxygen availability that are typically found in the upper part of the bioreactor near the feeding point, triggers the unfolded protein response (UPR) and thus impairs proper protein secretion. Methanol co-feeding with sorbitol was shown herein to reduce the UPR response and to restore productivity of secreted protein. •A scale-down system simulated heterogeneous conditions of large-scale bioreactors.•Transient oxygen and methanol levels led to a higher induction of CalB gene.•CalB secretion was impaired and correlated to unfolded protein response (UPR).•Sorbitol co-feeding strategy reduced UPR and restored CalB secretion.