Abstract
In liposome suspensions, enzyme reactions can be induced under the condition where the enzymes are isolated from the bulk liquid. The rate of liposomal enzyme reaction is often limited by the transfer of substrates from the bulk liquid to the liposome interior through lipid bilayer membranes. We have applied these characteristics of liposomes to modulate the stability and apparent reactivity of several oxidoreductases. Furthermore, the rate of liposomal reaction can be improved by suspending the enzyme-containing liposomes in gas-liquid flow, as observed for the oxidation of glucose in an external loop airlift bubble column. Permeability of 5 (6)-carboxyfluorescein through membranes of liposomes with mean diameter of about 100 nm increased under the fluid shear stress generated in a cone-and-plate geometry. Fluid shear stress in the airlift bioreactor was thus suggested to be responsible for the permeabilization of liposomes in the oxidation reaction. The liposomal enzyme would function as a fluid propertyresponsive catalyst in practical bioreactors.
