MEMBRANE SEPARATION COUPLED WITH ELECTROPHORESIS.

摘要

Concentration polarization phenomenon is studied in a stirred ultrafiltration cell with several different enzyme solutions. The filtration flow rate decreases significantly due to the concentration polarization of enzyme on the membrane surface. Vigorous stirring is applied to reduce the concentration polarization. However, enzyme will be deactivated in the polarization layer by the high shear from vigorous stirring. Instead of applying high stirring, an appropriate electric field is applied across the membrane to reduce concentration polarization of enzyme on the membrane surface. An electrochromatography with a new method of loading sample is developed to determine the electromobility of enzyme in a free solution. A water flow will be induced through the membrane due to the electrical charges on the membrane. The electrical charge characteristics of membranes are investigated by measuring the electroosmotic flow rate through the membrane. An experimental study of the ultrafiltration coupled with electrophoresis is carried out, achieving a high filtration flow rate as well as high bulk enzyme concentration.; In the same stirred ultrafiltration cell coupled with electrophoresis, the electrokinetic separation of small charged molecules such as acetate, phenylalanine, glycine and aspartic acid is studied. The charged molecules are much smaller than the molecular weight cut-off of the membrane (10,000) so that ions move freely through pores of the membrane. In the presence of an electric field, the electromigration of charged molecules enriches the permeate stream (filtrate). The concentration in the permeate stream is determined by the electromigration velocity of ions and the permeation rate of solvent (water) through the membrane. By adjusting the applied electric field strength and pressure across the membrane, a continuous concentration and separation of organic acids and amino acids is achieved in a cyclic operation.; As in a membrane reactor, the enzyme reaction is carried out in the stirred ultrafiltration cell coupled with electrophoresis. {dollar}beta{dollar}-Galactosidase enzyme reaction on ONPG and aspartase enzyme reaction on ammonium fumarate for aspartate production are used. The productivity of this membrane reactor is improved by an applied electric field. This is due to: (1) concentration polarization of the enzyme is prevented; (2) the small charged product is preferentially removed from the reactor. (Abstract shortened with permission of author.)