Immobilized enzyme

The spatial fixation of bacteria, cells or enzymes in the gel particles, capsules or even into circumscribed reaction chambers is called immobilization. The immobilization leads to a shift of the catalytic activity of submicroscopic and microscopic units in macroscopically tangible particles to achieve containment.

Methods

In the literature, several methods of immobilization have been described. The simplest method is to each other with sufficient affinity adsorption of the fabrics. However, since adsorbed molecules are subject to continuous leaching, other methods are usually used. These can be divided in different groups of methods:

Binding to a surface

The simplest form of immobilization is the binding of a biocatalyst in a carrier. The adsorption and the growth on the carrier is very gentle on the biocatalyst, but this form of immobilization is not appropriate for all catalysts and the bond often quite weak, resulting in a continuous loss of imobilisierten molecule by washing. The same is true for the ionic bond. By a covalent bond, although a more stable linkage is achieved, but it can lead to an impairment of the enzyme activity of the biocatalyst. By using very porous materials, a large, available for a bonding surface can be achieved. However, lying further inside biocatalysts due to the lower diffusion are often worse supplied with substrates.

Cross-linking

Larger particles with high catalytic activity can be prepared by cross-linking as well. Either the biocatalyst is directly cross-linked to itself (English crosslinking) or via a suitable support ( co - cross-linking). This method is not suitable for live cells, and is used almost exclusively for the immobilization of enzymes or cells killed with intact enzyme system. Again, damage to the enzymatic activity can not be excluded. However, this method has the advantage of increased stability of the immobilized system, often without decrease in activity.

Membrane separation

In the membrane separation of the biocatalyst is surrounded by a membrane. These immobilization methods include such diverse processes such as membrane reactors or hollow spheres. In membrane reactors, the cells are retained in free form in a more or less large reaction volume, and optionally concentrated. This method is very friendly, as it leaves the biocatalyst in his usual suspended form. However, these membrane reactors often mean a high equipment costs are so expensive and usually only suitable for sophisticated applications.

Entrapment

Entrapment in the biocatalysts are embedded in a matrix which allows an access of substrates and the flow of the products formed. Various forms of the resulting particles are conceivable. The mold is determined by the requirements of the subsequent application and the possible with the desired nature of the shaping material. By far the most common form is the spherical shape, which can be produced by various methods. Possible methods for this are Abtropfverfahren (with and without lateral venting flow ), vibration method and the jet cutting process.