DEVELOPMENT OF CHITOSAN-CONJUGATED MAGNETITE FOR MAGNETIC CELL-SEPARATION

For the purpose of separating microorganisms from culture broth by mag netic force, magnetic particles were conjugated with a polymer to prod uce polymer-conjugated magnetite (polymer-mag). Among 4 preparation me thods investigated-aminosilane coupling, glycidylsilane coupling, cros slinking, and co-precipitation-, polymer-mag prepared by co-precipitat ion showed the highest cell recovery and high dispersibility. When var ious cationic, anionic, and nonionic polymers were used to prepare pol ymer-mag and applied to the magnetic separation for Escherichia coli, magnetite conjugated with chitosan (chitosan-mag) gave the highest cel l recovery. In addition, E. coli cells could be recovered as the preci pitant only 1 min after chitosan-mag was added to a cell suspension, a nd a clarified supernatant was obtained. The amount of E. coli cells a dsorbed to the chitosan-mag was about 1 g-dry cells/g-chitosan-mag, an d cell recovery of over 90% was attained in wide pH range from 3.0 to 7.0. Of 12 microorganisms tested, 4 could be recovered with chitosan-m ag at recovery levels above 90%, and the adsorbed amounts exceeded 0.5 g-dry cells/g-chitosan-mag. Differences in adsorbed amounts were cons idered to be mainly due to the different zeta potential of the microor ganisms tested.