Analysis on Protein Stability in Tris Buffered Purified Bulk Solutions during the Freezing Process

摘要

Cryopreservation as a technique for the stabilization of solved biotechnologically produced pharmacological active agents (e. g. recombinant proteins) is gaining more and more importance as an industrial method. These recombinant proteins are solved in a buffer according to the fermentation process (upstream processing) and the purification process (downstream processing). Those buffered product solutions are named as purified bulk. Because of the time dependent loss of protein activity, the purified bulk gets frozen for reason of stabilization. But also the freezing process itself can damage the recombinant proteins in several ways. Possible mechanisms of protein damage are mechanical stress on the macromolecules due to ice formation, concentration effects and shifts of the buffer-pH depending on the change in temperature. The effects of changes in the pH are well known in proteins. The pH-dependent protein damage is related to the freezing process and can only be estimated by an analysis of the pH-properties of a purified bulk. The focus of this study is the discussion on the effect of the pH-shifts during the freezing of Tris(hydroxymethyl)-aminomethane (Tris) buffered purified bulk solutions and on the prevention of damaging effects on the protein agent.