DETAILED DESCRIPTION OF THE INVENTION In the process according to the invention, glucose isomerase crystals are cross-linked by means of a dialdehyde, such as glutaraldehyde, and a compound containing at least one amino group, such as an ammonium compound, amine, or amino acid, preferably an ammonium salt or lysine.
Several amines and amino acids are suitable for use.
It is likewise evident that in addition to glutaraldehyde, many other dialdehydes and substances reacting with amino groups, known as cross-linking reagents, can be used in the process.
The activity of a solid crystalline enzyme prepared by means of the process according to the invention is very high.
Depending on the conditions used for its production, its activity may be almost the same as that of a free enzyme.
Solid crystalline enzyme can be used as such as a column filler in a continuous process.
It is extremely stable and withstands mechanical stress well.
If desired, cross-linked crystals can be further bound to form larger bodies, e.
g.
in spherical, sheetlike, bandlike or the like in shape, in known chemicophysical ways.
Enzyme preparations so obtained can withstand various mechanical treatments.
Those skilled in the art will recognize that the cross-linking process, as disclosed herein, can be used to prepare insoluble preparations of virtually any crystalline enzyme which has not, generally because of its amino acid composition, heretofore been found to be conducive to cross-linking.
In the following, the process according to the invention will be described in more detail.
Preparation of Crystalline Glucose Isomerase used as Raw Material Ammonium sulfate (about 10% by weight) is dissolved in a glucose isomerase solution (1 to 10% by weight of isomerase determined as dry protein).
The solution is cooled slowly to about 1.
degree.
to 2.
degree.
C.
under constant stirring.
An essentially complete crystallization of the isomerase thereby occurs (more than 95%).
In place of ammonium sulfate, magnesium sulfate or sodium sulfate, for instance, can be used as a crystallization agent
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Molecular Biology 
