Enzymes represent effective and sometimes preferable catalysts for a wide range of important organic reactions on account of their high chemo-, regio-, and enantio-selectivity. However, in many cases, substrates of interest are sparingly soluble in water whereas enzymes are typically active in the water phase. Thus, aqueous–organic biphasic reaction systems are often employed to achieve high substrate concentration and enhanced productivity. Very recently, Pickering emulsions, which are emulsions stabilized by colloidal particles, have emerged as a novel biphasic system for improving enzyme activity. Using Pickering emulsions not only facilitates mass transfer between the two liquid phases but also simplifi es product separation, as colloidal particles are easily recoverable. As a further evolution, Pickering interfacial biocatalysis where enzyme immobilized particles are employed as a whole to stabilize emulsions has become a more appealing proposition. In such a case the location of an enzyme at Pickering emulsion interfaces maximizes the oil–enzyme–water interfacial areas and increases the availability of the enzyme for substrates from both phases. Although promising, due to issues of low stability and environmental sensitivity, the application of enzymes for Pickering emulsion-based biocatalysis is still challenging. In particular, the enzyme immobilization process and prolonged exposure to aqueous–organic interfaces easily result in changing enzyme natural structures, alternating enzyme activity, and restricting re-usability.
2009-2016 Changchun Institute Of Applied Chemistry, Chinese Academy Of Sciences, All