Mini review for niche downstream processes

We review here several niche downstream purification processes that are not covered by other articles in this special issue. The first is the use of activated carbon to capture contaminants and clarify culture medium for purification of proteins, including antibodies. Flow-through operation of the activated carbon filter showed over 80 % recovery of antibodies with 10--fold reduction of host cell proteins and effective lipopolysaccharide and virus removal. The second is salt or arginine-tolerant column chromatography, in which the respective resins, such as hydroxyapatite and mixed-mode resins, can bind proteins in the presence of salt or arginine at high concentrations. Effective use of arginine was also suggested in size exclusion and affinity chromatography. The last is the isolation of proteins using gel electrophoresis and simple extraction procedure. These technologies offer simple and cost-effective methods for purifying proteins and protein complexes in the native state.