Cross-Linked Enzyme Aggregates (CLEAs) in Organic Synthesis

The immobilization of a wide variety of enzymes-hydrolases, oxidoreductases, lyases, and transferases-as cross-linked enzyme aggregates (CLEAs) and their applications in organic synthesis are reviewed. The examples are categorized on the basis of the functionality of the reaction product; e.g., alcohols, amines, carboxylic acids and derivatives, carbohydrates, amino acids and peptides, and even polyamides. The CLEA technology is a simple and effective way of immobilizing enzymes that offer several advantages when compared to the corresponding free enzymes, such as increased thermal stability, facile recovery and reuse, and high productivities as compared to carrier-bound enzymes. Selectivities are generally as high as, or even higher than, with the free enzymes. Co-immobilization of two or more different enzymes affords Combi-CLEAs which can be used effectively in one-pot, enzymatic cascade reactions.