Because enzymes function nearly to perfection in living systems, there is great interest in how they might be harnessed to carry on desired reactions of practical value outside of living systems. The potential value in the use of enzymes (separate from the organisms that synthesize them) is undeniable, but how to realize this potential is another matter.
Practical use of separated enzymes is not new. Hydrolytic enzymes isolated from bacteria were widely used for a brief period to assist in removing food stains from clothing, but many people suffer allergic reactions to enzymes used in this way, and the practice was stopped. A major objective in enzyme technology is to develop an enzymatic process for the hydrolysis of cellulose to glucose (Section 20-7A). Some microorganisms do possess the requisite enzymes to catalyze the hydrolysis of the \(\beta\)-1,4 glucoside links in cellulose. If these enzymes could be harnessed for industrial production of glucose from cellulose, this could be an important supplementary food source. Technology already is available to convert glucose into ethanol and ethanoic acid, and from there to many chemicals now derived from petroleum.
A difficult problem in utilizing enzymes as catalysts for reactions in a noncellular environment is their instability. Most enzymes readily denature and become inactive on heating, exposure to air, or in organic solvents. An expensive catalyst that can be used only for one batch is not likely to be economical in an industrial process. Ideally, a catalyst, be it an enzyme or other, should be easily separable from the reaction mixtures and indefinitely reusable. A promising approach to the separation problem is to use the technique of enzyme immobilization. This means that the enzyme is modified by making it insoluble in the reaction medium. If the enzyme is insoluble and still able to manifest its catalytic activity, it can be separated from the reaction medium with minimum loss and reused. Immobilization can be achieved by linking the enzyme covalently to a polymer matrix in the same general manner as is used in solid-phase peptide synthesis (Section 25-7D).
Enzymes also have possible applications in organic synthesis. But there is another problem in addition to difficulties with enzyme stability. Enzymes that achieve carbon-carbon bond formation, the synthetases, normally require cofactors such as ATP. How to supply ATP in a commercial process and regenerate it continuously from ADP or AMP is a technical problem that has to be solved if the synthetases are to be economically useful. This is a challenging field of biological engineering.
Contributors and Attributions
John D. Robert and Marjorie C. Caserio (1977) Basic Principles of Organic Chemistry, second edition. W. A. Benjamin, Inc. , Menlo Park, CA. ISBN 0-8053-8329-8. This content is copyrighted under the following conditions, "You are granted permission for individual, educational, research and non-commercial reproduction, distribution, display and performance of this work in any format."