Organic-Soluble Enzyme Nano-Complexes Formed by Ion-Pairing with Surfactants

The solubilization of enzymes in organic solvents for non-aqueous biocatalysis has attracted considerable attention since the homogeneous distribution accounts for a drastically improved reaction efficiency compared to enzymes dispersed as aggregates in an organic phase. This chapter highlights ion-pairing as a valuable and facile method to make enzymes soluble in organic solvents. Ion-pairing denotes the formation of a nano-complex, in which a single enzyme molecule in the core is surrounded by counter-charged surfactant molecules. The special architecture of this nano-complex exposes the surfactant hydrophobic group toward the bulk solvent and renders the complex sufficiently soluble in organic media. This chapter also describes the underlying principle of ion-pairing as well as simple preparation and characterization techniques to yield highly active enzyme–surfactant nano-complexes. The general applicability of this technique is demonstrated on the base of the hydrolytic enzyme α-chymotrypsin (α-CT) and the redox enzyme glucose oxidase (GO _x ).