Downstream processing diafiltration

Diafiltration is a process whereby an ultrafiltration system is utilized to reduce or eliminate low molecular mass molecules from a solution and is sometimes employed as part of biopharmaceuti-cal downstream processing. In practice, this normally entails the removal of, for example, salts, ethanol and other solvents, buffer components, amino acids, peptides, added protein stabilizers or other molecules from a protein solution. Diafiltration is generally preceded by an ultrafiltration step to reduce process volumes initially. The actual diafiltration process is identical to that of ultrafiltration, except for the fact that the level of reservoir is maintained at a constant volume. This is achieved by the continual addition of solvent lacking the low molecular mass molecules that are to be removed. By recycling the concentrated material and adding sufficient fresh solvent to the system such that five times the original volume has emerged from the system as permeate, over 99... 

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