Increased glycosylated L-asparaginase production through selection of Pichia pastoris platform and oxygen-methanol control in fed-batches

Currently, only the biopharmaceutical L-asparaginase (ASNase), a chemotherapy agent, from bacteria is approved for clinical use. Although it is efficient, it causes severe side effects due to its origin. Therefore, new sources are investigated to reduce immunogenicity. Moreover, it is urgent to enhance protein stability, folding and kinetics with post-translational modifications, such as glycosylation. Aiming at these attributes, this study focused on the production of a glycosylated L-asparaginase of Dickeya chrysanthemi expressed by Pichia pastoris Glycoswitch (R). Producer strains of Pichia, one with auxotrophy for histidine and another prototrophic were compared by using a complex medium in flasks and a synthetic medium in a bioreactor. The prototrophic strain showed higher productivity than the auxotrophic in both scales. Following, two induction strategies with the prototrophic strain were executed: methanol pulses and a DO-stat. The latter resulted in 2-fold more maximum volumetric activity. Lastly, the glycosylation analysis of the final product showed that the site Asn(170), which is associated with allergies in patients, was glycosylated, thus, reducing potential immunogenic effects. Therefore, this study showed that the prototrophic strain was the most suitable L-asparaginase producer and that methanol-oxygen control in bioreactor enhanced the production of a glycosylated ASNase. (AU)