Immobilized Enzymes and their Activity Losses
Immobilized enzymes are used in various industries, such as the food and pharmaceutical industries, for bioremediation, or in detergent and textile production, and many more.
Aside from improved operating stability, volume specific biocatalyst loading, recyclability, and simplified downstream processing, immobilized enzymes often prove advantageous in industry compared to soluble enzymes. However, they might also come with limitations such as reduced enzyme activity or worsened mass transport. A brief introduction to immobilized enzymes and their activity losses is provided here.
A tutorial review authored by Liese and Hilterhaus (Chem. Soc. Rev., 2013) lists key phenomena and factors that individually or jointly contribute to the loss of apparent enzymatic activity in biocatalytic processes:
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Thermal deactivation
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Oxidation
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Organic solvents or high reactant concentrations
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Interfacial areas of gas-liquid or liquid-liquid
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Chemical instability of the support
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Deactivation by a product
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Deactivation by a starting material
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Abrasion due to shear forces, stirrer and particle–particle collision
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Desorption of metal ions required for activity and/or stability
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Leaching of the enzyme from the carrier
The authors conclude that although determining the primary cause of activity loss is difficult, it is vital to finding an effective remedy. Sometimes it might be a process condition like temperature, solvent choice, or reactant concentration. Inhibition by reactants or products is also a frequently critical factor. According to this review, a better-suited type of reactor can be used in the latter case. - However, the question remains: