Purification and Concentration of Enzymes

Enzymes are proteins with molecular weights in the range of20,000 to 

000 dalton and are predominantly produced in small batch fermenters. UF often combined with diafiltration is widely used in the industry to produce a variety of enzymes such as trypsin, proteases, pectinases, penicillinase and carbohydrates. 

UF performance, however, may be influenced by process variables such as pH, nature of ions and ionic strength, temperature and shear. For example, Melling has reported the effect of pH on the specific enzyme activity of E-coli penicillinase in the pH range 5 to 8. Effects of shear inactivation associated with piunping effects are described by O Sullivan et al. Recessed impeller centrifugal pumps or positive displacement pumps may be used to minimize enzyme inactivation due to shear. 

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In Chapters 13 and 14 of this book the applications of conventional chemical catalysts were described. The use of enzymes or whole cells as catalysts for chemical transformations is well known. They can bring about various reactions at ambient temperature and pressure and afford high reaction velocities. In fact, enzymatic reaction sequences may be designed to give the ideal efficiency embodied in the second law of thermodynamics. Thus, hundreds of compounds that are very difficult to prepare by purely chemical methods may be obtained quite readily and economically with the help of enzymes. Until recently, most laboratory investigations and manufacturing processes employed soluble enzymes in dilute aqueous solutions. Before use, the required enzyme must be obtained from biological sources as a concentrated extract. It is not uncommon for a particular type of cell to contain many proteins in addition to the one desired. Therefore, the purification and concentration of enzymes in preparation for use is a very cumbersome process. When used in solution, enzyme catalysts are invariably lost after each batch operation. The use of immobilized enzymes and whole cells has been proposed as a means that could eliminate such losses and preserve hard won stocks of specialized enzymes. 

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