Effect of pH on Proteolytic Degradation of Consensus Interferon-α Expressed by Pichia pastoris

Abstract:

We observed the heterogeneity of consensus interferon (cIFN) expressed by Pichia Pastoris, such as aggregation and degradation. The effect of induction pH on degradation of cIFN was studied in a 5-L bioreactor. The heterogeneity of cIFN was less serious when induced at pH 4.0~5.0. The bioactivity of the fermentation supernatant reached 2.5×108 IU/mL when pH was controlled between 4.0 and 5.0. To seek the reason of cIFN degradation, we analyzed the activity of protease and cell mortality by flow cytometry. At lower pH, cell mortality was higher and more protease was released. Protease activity increased at higher pH. The proteolytic degradation of cIFN was enhanced at either high or low pH. The cIFN was degraded entirely when pH was 7.0, where the protease had its optimal pH.