Characterization of magnetic ion-exchange composites for protein separation from biosuspensions.

Downstream processing is a major issue in biotechnological production. A multitude of unit operations with nonsatisfying yield are often used to reach the desired product purity. Direct recovery technologies such as high-gradient magnetic fishing (HGMF) are advantageous because of their ability to separate the desired product in early stages from crude cultivation broths. However, the use of magnetic particles to capture valuable biotechnological products is often linked to the drawback that support particles are expensive and not available in greater quantities. This current work presents new composite magnetic particles that can be used in biotechnology. They are manufactured by a spray drying process. During this process, the nanosized magnetite particles as well as functional ion-exchange nanoparticles are integrated into one particle in which they are linked by a matrix polymer. The production procedure is flexible, scalable, and therefore economical. These particles have good adsorption capacities of up to 85 mg/g adsorbed protein and good binding kinetics. They are resistant to harsh conditions such as short ultrasonic treatment or extreme pHs. In order to test their usefulness in biosuspensions, model proteins were separated using these particles. The anion and cation exchanger particles separated lysozyme (LZ) or BSA from cultivation suspensions. The selectivity of recovery was dependent on other proteins present as is usual for ion-exchange binding mechanisms.

Characterization of protein capacity of nanocation exchanger particles as filling material for functional magnetic beads for bioseparation purposes.

In this study we describe the synthesis and characterization of nanocation exchanger particles (NCEX) as the functional filling material for magnetic beads. Polystyrene NCEX particles were synthesized from styrene via a mini-emulsion polymerization. The coupling of cation exchanger groups was done with chlorosulfuric acid after the polymerization reaction. The NCEX particles have an average diameter of 160-260 nm. Their ion exchange capacity amounts up to 4.58 mval/g. In an adsorption experiment it was possible to adsorb 192 mg lysozyme/g NCEX. Depending on the equilibrium concentration of lysozyme in the bulk solution 70-85% of the attached protein was desorbed. NCEX particles were used to produce magnetic beads with cation exchanger properties. Therefore an innovative production process for the synthesis of magnetic beads from different single components was used. The produced magnetic beads contained 40 wt % NCEX material and showed an ion exchanger capacity of 2 mequiv/g. It was possible to adsorb 75 mg lysozyme/g magnetic beads with a maximum recovery rate of 95%.