Process Flow Sheet

Figure 16.9 shows a typical process flow sheet for a Protein A step along with the specific purpose of some of the segments. The rationale for the development of certain segments in the Protein A step has already been mentioned in Section 16.4.2 and this section outlines some other general guidelines. Equilibration of the column is usually done under neutral conditions (~pH 6.0 to 7.5) and the commonly used buffer systems are tris, phosphate, or citrate. The equilibration buffer also contains moderate concentration of salt to minimize nonspecific electrostatic interactions. Commonly used buffer systems during elution are citrate and acetate which have good buffering capacity in the lower pH range. It is desirable to avoid the use of halide containing salts (such as NaCl) in the buffers at lower pHs to avoid corrosion of stainless steel tanks. Finally, if an acidic strip is followed by a sodium hydroxide regeneration solution, it is recommended to flush the column (usually with the equilibration buffer) to prevent acid/base reactions inside the column.

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