ABSTRACT
Immobilized biocatalysts offer several benefits in comparison to the application of soluble free enzymes or free cells. A biocatalyst bound to a solid surface allows for its reutilization and its use in continuously operated reactors such as columns or stirredtank reactors is facilitated. Additionally, the immobilization of a
biocatalyst also enables an easier separation from the media and downstream processing. When using purified enzymes, the costs often constitute a significant part of the total production process. For this reason, recycling of the immobilized biocatalyst may lead to an overall cost benefit. Magnetic micro-and nanocarriers have been known for many years in standard applications such as medicine, bioscience, and bioseparation as well as purification processes. These sorts of solid particles are commonly used in such methods as immunodetection, genetic transformation, bioanalytics, magnetic resonance imaging and drug delivery. In contrast to these well-known mostly biomedical applications using magnetic micro-and nanosupports in biocatalysts immobilization is a developing field that needs to be further explored. Featuring several interesting qualities, the development of new applications gives promising solutions for downstream-and enzymatic processes. Magnetic micro-and nanocarrier systems offer a comparably large specific surface area due to their small size between 10 nm and 10 µm. The magnetic nature offers a simple solution to postreaction separation processes. However, in contrast to relatively larger porous particles, they mostly feature compact non-porous surfaces. This facilitates the transport kinetics in comparison to porous carriers. For the evaluation of this potential benefit, several enzyme and reaction-specific aspects have to be considered. Activity yield, recyclability, and stability are the three basic considerations concerning the utilization of immobilized biocatalysts. An important point affecting all these aspects is the choice of the carrier.
