Method for producing tagatose by immobilized multi-enzyme system

A method for preparing an immobilized multi-enzyme system, characterized in that the immobilized multi-enzyme system is prepared by uniformly mixing a porous polydopamine microsphere with a multi-enzyme mixture which is used for producing tagatose;

• the multi-enzyme mixture comprises glucan phosphorylase, phosphoglucomutase, phosphoglucose isomerase, tagatose 6-phosphate 4-epimerase and tagatose 6-phosphate phosphatase;
• the enzymes of the multi-enzyme mixture are attached in an amount as follows, that is, each gram of the porous polydopamine microsphere is attached with 1,500-2,500 U of glucan phosphorylase, 1,500-2,500 U of phosphoglucomutase, 1,500-2,500 U of phosphoglucose isomerase, 1,500-2,500 U of tagatose 6-phosphate 4-epimerase, and 1,500-2,500 U of tagatose 6-phosphate phosphatase;
• the porous polydopamine microsphere is prepared by a method comprising the following steps:
• (1) pouring a sodium carbonate aqueous solution into a calcium chloride aqueous solution, stirring, carrying out solid-liquid separation, and collecting a solid product, which is a porous calcium carbonate microsphere;
• (2) mixing the porous calcium carbonate microsphere with a dopamine solution, carrying out solid-liquid separation, and collecting a solid product, which is a polydopamine-calcium carbonate microsphere;
• and
• (3) mixing the polydopamine-calcium carbonate microsphere with ethylenediamine tetraacetic acid (EDTA) to conduct reaction, carrying out solid-liquid separation, and collecting a solid product, which is the porous polydopamine microsphere.