Membrane-supported aqueous-phase enzymatic conversions in organic solvents.

摘要

A new concept membrane immobilized enzyme bioreactor is developed. Enzyme is placed in a thin film of water strongly associated with the inner surface of a hydrophilic microporous membrane and is either adsorbed on the membrane or freely dissolved in an aqueous phase. Substrate dissolved in a water-immiscible organic solvent is convectively permeated through the membrane and converted into product by the enzyme reaction. The permeation flux is controlled by transmembrane pressure, therefore, efficient mass transfer with continuous operation is achieved.; This concept was tested using tyrosinase-catalyzed oxidation of p-cresol in chloroform and the effects of the operating parameters on performance were studied. The initial reaction rate quickly decreased and was followed by relatively stable period. The experimental results showed that the initial activity loss was due to enzyme transport in both axial and radial directions. Approaches to reduce the movement of enzyme and to improve activity are suggested. Water content and permeation flux were the most important parameters effecting performance for the system.; A mathematical model describing the behavior of the system was developed using experimentally determined parameters. By separating the effect of water content and permeation flux on the enzyme activity, the optimal operating conditions could be determined.; Also, alcohol dehydrogenase-catalyzed oxidoreduction of alcohol and aldehyde was employed to test the applicability of the technique. It appears that the membrane supported aqueous-phase enzyme reactor is also useful with enzymes requiring cofactors.; The experimental results using two model enzyme-catalyzed reactions indicate that although the initial decrease of activity remained a problem, membrane supported aqueous-phase is a useful technique with enormous potential for enzyme-catalyzed reactions.