Glucose Isomerase,Catalytic Activity,Immobilized Bacterial Cells,Batch Cultures

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	Glucose Isomerase - Commercial glucose isomerase is, in fact, D-xylose ketol-isomerase, and is produced by several bacteria (Table 10.10). Some improved strains produce the enzyme constitutively. The bacteria are grown in aerated batch cultures at 30°C and 7.0 pH for 2-3 days. The enzyme is intracellular, and is best used in the form of immobilized cells. The cells are suitably treated to increase their stability and catalytic activity.
Purified glucose syrup is heated to remove dissolved O2 and increase glucose concentration to 40%. pH is adjusted between 7 and 8. The syrup is passed through a column containing immobilized bacterial cells with glucose isomerase activity; the temperature is kept at 60°C. The enzyme longevity, under practical conditions, is 2,000-4,000 hr optimally; 20 tons or more product can be processed per kg of the catalyst. The end product of glucose isomerase action is a nearly 1 : 1 mixture of glucose and fructose; this has increased sweetness as compared to glucose and is virtually identical with 'invert sugar obtained from beet or cane sugar (sucrose).