Enzyme entrapment, biocatalyst immobilization without covalent attachment

In entrapment an active species, which is often a catalyst, is trapped within a material by a solid or gel forming event; thus, it becomes dispersed within the solid or semi-solid matrix. Entrapment methods can be used to immobilize isolated enzymes and render them more stable, and easier to separate and recycle. Entrapment immobilization methods are well established for whole cell biocatalysis. Despite this the applications of entrapment towards isolated enzyme immobilization have lagged the use of covalent attachment and crosslinking methods. In this review entrapment methods are contrasted with other methods of enzyme immobilization and literature methods of enzyme entrapment are reviewed. A key advantage of this approach is that no formal interaction with the protein is required, but this must be balanced against the threat of enzyme leaching, or introduction of mass transfer limitations. The main methods of entrapment are characterized, and some recent innovations are highlighted.