Introduction to Protein Isolation and Purification

While plants and animal organs are often good sources of specific enzymes, such as a-chymotrypsin from bovine liver or peroxidase from soybeans, the vast majority of enzymes are obtained from microorganisms, mostly bacteria but also yeast or fungi. To obtain enzymes from microorganisms in known quantities and quality, at any time of year independently of nature s growth and harvest cycle, the appropriate production processes have to be developed. 

Should a higher degree of purity be required, final purification steps are added to the procedure. Final purification typically includes various forms of chromatography such as ion-exchange and, commonly as the last step, affinity chromatography. Dialysis steps to change the salt level are added as required. A pure enzyme is either stored with excipients in liquid form or is lyophilized, i.e., dried by sublimation of water. 

During downstream processing, a trade-off has to be managed between purity, yield, and concentration level  

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