Open Access
Review
Table 3
Overview of methods for NK isolation and purification
| Method | Principle | Advantage/Shortcoming | Enzyme activity recovery/% | Purifica-tion ratio |
|---|---|---|---|---|
| Column chromatography[103-104] | After filtration, centrifugation, and salting out, the sample is purified using column chromatography | Higher purification times and recoveries/High cost, complex operation, long processing time, not easily scalable for industrial production | 42.1 | 19 |
| Ultrafiltration[105-106] | Separation of NK using differential pressure-driven membrane separation, followed by chromatography | Large processing capacity, high extraction efficiency, convenient operation/Wide transmittance range; the filter membrane is prone to contamination | 92.3 | 2.36 |
| Two-phase aqueous extraction[103,107] | Separation based on the differing solubility of biomolecules between two phases | Low energy consumption, minimal environmental pollution/Higher cost, lower selectivity, only suitable for coarse separation | 81 | 3.52 |
| Reverse colloidal extraction[103] | Surfactants form microspheres in a non-polar solution, which are transferred to the aqueous phase for separation | High selectivity, simple operation, low cost/ Complex system, uncontrollable conditions | 80.2 | 2.5 |
| Affinity particle adsorption[103,108] | NK is adsorbed by affinity particles in the crude enzyme solution | Simple operation, high efficiency, does not negatively affect protein activity, easy to separate/Expensive ligand and complicated preparation | 85 | 8.7 |
| Expanded bed methods[98,109] | Proteins are separated by electrostatic adsorption of oppositely charged proteases on an ion exchange column | Avoids NK inactivation, simplifies the separation process, reduces purification time, and improves product recovery/More complex equipment and control, higher cost | 95 | 8.2 |
| Three-phase partitioning[110] | Ammonium sulfate is mixed with n-butanol, precipitating protein from the mixture | Moderate action conditions and low cost/Low selectivity and specificity, limited large-scale production | 129.5 | 5.6 |
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