Immobilization of GlucoseIsomeraseOne of theways to reduce the cost of production of GI is to recover it efficiently andreuse it several times. Immobilization of GI offers an excellent opportunityfor its effective reuse. The largest market for GI is for its immobilized form.Development of immobilized GI has been a subject of great interest. The use ofGI is expensive because it is an intracellular enzyme and large quantities areneeded to compensate for the high Km for glucose.
Therefore, it isimportant to immobilize GI for its industrial applications. Several methods forimmobilizing GI have been described. However, only a few are economical andyield enzyme preparations with properties that are suitable for commercialproduction of HFCS. Two main methods are used for immobilization of GI:cell-free enzyme immobilization and whole-cell immobilization. Cell-freeimmobilization. Solubleenzymes that are immobilized to a support structure have excellent flowcharacteristics suitable for continuous operations, in contrast to whole-cell immobilizedsupports, and offer considerable savings in terms of capital equipment. Materialsfor immobilization includes · DEAEcellulose.
· Porous alumina · Controlled-pore alumina in thepresence of Co21 · Coimmobilized GI on large-porepolyethylene discs by permeating the discs with a solution of polyacrylonitrilein dimethyl sulfoxide and finally fixing it with glutaraldehyde. · Cellulose acetate Whole-cellimmobilization. BecauseGI is an intracellular enzyme, whole-cell immobilization is the method ofchoice for most of the commercially available immobilized GIs. Methods ofachieving this includes:1.
Spray-drying whole cells containing GI, adding inorganic salts suchas magnesium hydroxide to the fermentation broths of Streptomyces or Arthrobacterspecies, filtration and drying of the cake is a straightforward method toimmobilize cells. 2. Physical entrapment of whole cells in polymeric materials was usedas an immobilization method3. Chemical entrapment of cells in a membrane followed by cross-linkingwith glutaraldehyde was used to prepare an immobilized GI.