Scaling Up an Immobilized Enzyme System

Abstract

The development of an immobilized enzyme system for commercial application involves a series of decisions and compromises beginning with the choice of enzyme support and ending with the decision on operational mode. Each step is dependent on the other steps, and all the steps influence the overall economics of the final process. Compromises need to be made about the support, method of enzyme attachment, reactor type, kinetic behavior, and operating strategy. Selection of the enzyme carrier and its composition will have a major effect on the pH optimum, metal requirements, and overall performance of the immobilized enzyme system. The reactor type and its behavior will also affect performance. For commercial applications the fixed-bed reactor is generally the reactor type of choice. Knowledge of the appropriate kinetics is necessary to achieve the desired product quality and to reduce cost. One important kinetic parameter is reaction velocity under real world conditions. Rate expressions must take into consideration back-mixing and mass transfer limitations, both internal and external to the immobilized enzyme particles. In addition to understanding kinetic behavior, one must devise a proper operating strategy for producing the greatest amount of product at the least cost, while maintaining constant productivity over time. The success of any scale-up will be determined by the final processing cost as compared to that of the alternatives.

Immobilized Biocatalysts

“…The only two fixing agents approved for the preparation of immobilized glucose isomerase in high-fructose corn syrup production are diethylaminoethyl cellulose (DEAE cellulose) and glutaraldehyde [280]. Examples of pending or unsuccessful petitions for GRAS affirmation are given in [280], [281]. Cross-linking agents are highly reactive and often toxic.…”

“…The U.S. regulations require that the fixing agents consist of GRAS substances or that the immobilized enzyme preparation be washed thoroughly to remove fixing-agent residues. The only two fixing agents approved for the preparation of immobilized glucose isomerase in high-fructose corn syrup production are diethylaminoethyl cellulose (DEAE cellulose) and glutaraldehyde [280]. Examples of pending or unsuccessful petitions for GRAS affirmation are given in [280], [281].…”

Biotransformations in Small‐Molecule Pharmaceutical Development

“…197 CLECs are produced by crystallization of purified enzyme and subsequent cross-linking, usually with glutaraldehyde, which is an FDAapproved fixing agent for the immobilization of glucose isomerase used in high-fructose corn syrup production. 198 CLECs proved to be excellent biocatalysts, displaying high activity, stability and separation properties, as demonstrated by their use in the resolution of the bisfuran alcohol intermediate of brecanavir (Scheme 1.33). Unfortunately, enzyme purification and crystallization can be labour intensive to develop and inefficient, resulting in an extremely active but highly expensive catalyst.…”

Immobilized Lactase in the Biochemistry Laboratory

“…Immobilized enzyme technology is not new. Many enzymes, or whole bacterial cells representing "bags" of enzyme, have been immobilized and used in several industrial processes such as antibiotic transformations, steroid modification using ketosteroid dehydrogenase, D-amino acid production using aminoacylase, and production of high-fructose corn syrup using glucose isomerase or invertase (1)(2)(3)(4)(5)(6)(7)(8)(9). Unique biosensors have been developed by immobilizing enzymes onto films that cover electrodes (6 ).…”