BINDING OF LYSOZYME ONTO A CATION-EXCHANGE MICROPOROUS MEMBRANE CONTAINING TENTACLE-TYPE GRAFTED POLYMER BRANCHES

Ion-exchange adsorption of lysozyme to the sulfonic acid (SO3H) group on polymer chains grafted onto microporous polyethylene hollow-fiber m embranes was examined. The lysozyme solution was forced to permeate ac ross the hollow fiber. Diversely anchored SO3H groups, i.e., SP and SS groups, were introduced into the membrane by reaction of the glycidyl methacrylate-grafted membrane with propanesultone and sodium sulfite, respectively. The resulting SP and SS group-containing membranes, des ignated as SP-T and SS-T fibers, respectively, had 95 and 77 % water f lux of the original membrane, respectively. The binding capacity of ly sozyme as a function of the SO3H group density was compared between th e SP-T and SS-T fibers from measurement of the ion-exchange breakthrou gh curves during the permeation of lysozyme solution across the SP-T a nd SS-T fibers. The binding capacity of lysozyme to the SP-T fiber rem ained constant, independent of the SP group density, whereas that to t he SS-T fiber increased linearly with increasing SS group density. Thi s difference was explained by means of a model whereby lysozyme adhere s onto the SP group-containing grafted polymer branches, while the SS group-containing grafted polymer branches hold lysozyme in a tentacle- like manner.