1. Field of the invention
This invention relates to a method of producing palatinose for sucrose using immobilized .alpha.-glucosyl transferase.
2. Description of the Prior Art
Palatinose is a reducing disaccharide and it has been confirmed that palatinose is a natural component in honey and cane juice. The sweetness of it is about half of that of sucrose.
The molecular structure of palatinose is 6-O-.alpha.-D-glucopyranosyl-D-fructose in which glucose is bonded to fructose at 1,6-position. Palatinose is also called as isomaltulose.
In regard to a method of producing palatinose, a method is known wherein enzyme in a form of living or dead cells of Protaminobacter rubrum is added to an aqueous solution of sucrose to convert sucrose into palatinose and then the enzyme is separated from the solution as disclosed in West German Pat. No. 1,049,800. In this case, the separation of the enzyme is performed by centrifugal separation.
According to the technical level, .alpha.-glucosyl transferase forming palatinose from sucrose is produced by cultivating a certain kind of bacteria, i.e., Protaminobacter rubrum, Serratis plymuthica, etc., in the presence of sucrose. Since the enzyme associates with the cell of the bacteria, a mass of their cells itself can be used as an enzyme preparation.
Therefore, in the case of producing palatinose from sucrose, a mass of cells containing .alpha.-glucosyl transferase is added to an aqueous solution of sucrose in a concentration of 20-30% and the reaction is performed by stirring the mixture while controlling the mixture at a temperature of 20.degree.-30.degree. C. and a pH of about 7. The reaction period of time depends upon the amount of enzyme, the reaction temperature, etc., but, since the remaining amount of sucrose in the reaction mixture becomes very slight usually in about 20 hours after the addition of the cells, this point is defined as the end of the reaction, and then the cells are removed from the reaction mixture to provide an aqueous transparent solution of palatinose, which is purified by ion-exchange resin, etc., and then concentrated under reduced pressure to crystallize palatinose.
In the above procedure, the cells are removed from the reaction mixture usually by a centrifugal separation method, but, since the difference in specific gravity between the cells and the reaction mixture is small and also the size of the cells is very small, the separation efficiency is very poor and hence a very large installation is required for practicing the method, which gives a large problem in the case of practicing the method industrially.