Large-scale purification of enzymes

For an enzyme to be employed as a reagent in any field, be it clinical chemistry or organic synthesis, it must first be purified to a degree that removes any other enzyme capable of catalysing undesirable side-reactions. This may or may not mean purification to homogeneity. For the enzyme to be commercially viable, purification must yield tens or hundreds of grams of protein. On this scale, the availability of sufficient starting material may pose a problem, particularly for animal tissues. For this and other reasons, bacteria may provide the most valuable source of enzymes. Bacteria are readily produced in enormous quantities and, by virtue of their diverse metabolism, contain many enzymes not present in other organisms. Furthermore, the enzymes from thermophilic species often show a desirable increase in stability under the arduous conditions which may be encountered in a reactor. The preparation of enzymes on this scale from bacteria, or any other source, can usually be accomplished by the application of the normal range of techniques available to the protein chemist. Thus precipitation methods, gel filtration, ion exchange and affinity chromatography are all valuable. A major difference between this and normal laboratory-scale scale purification is cost; large-scale enzyme purification requires a considerable investment in equipment, materials and manpower. This cost must be viewed in terms of the value of the product.