反应详情

An aqueous solution containing 80 g. of dextrose (d.b.) and 13.3 mg. of Mg(OH)2 per 100 ml. was prepared. The solution was stirred for at least one hour (preferably overnight) to equilibrate. The pH was adjusted to 8.5 at room temperature with 3 N KOH. 193.9 g. of substrate (about 150 ml.) was added to a 1-liter stainless steel beaker covered with a center-holed watch glass containing an additional hole near the edge. The sample was placed in a 60°C water bath, and stirred for 15 minutes, while maintaining a pH of 8.0 with 3 N KOH. The substrate was sparged with nitrogen at a moderate rate using a gas dispersion tube placed through the peripheral hole of the watch glass. A pre-weighed amount of xylose isomerase-basic magnesium complex containing from 1,000 to 3,000 units of bound isomerase was added using 50 ml. of 60°C water to transfer the material to the stainless steel beaker. This yielded a reaction mixture containing 60 g. of dextrose and 10 mg. of Mg(OH)2 per 100 ml. and an isomerase dosage level of from 8.3 to 25.0 units per gram of dextrose. The reaction mixture was adjusted to pH 8.0, and digested for exactly two hours after enzyme addition. The material was filtered immediately by vacuum through an 11-cm. Whatman 541 paper and the pH of a 500 ml. portion of the filtrate was adjusted to about 2.5 with 1.0 N perchloric acid. The dry substance content of the inactivated sample was determined by refractive index measurement and the levulose concentration by using spectrophotometric or polarimetric procedures. From the amount of levulose produced, effective isomerase ("retained isomerase activity") activity was calculated using the following equation: ##EQU2## where: V = reaction volume, ml.;

1. additionAn aqueous solution containing 80 g
2. customwas prepared
3. additioncontaining an additional hole near the edge
4. customwas placed in a 60°C
5. stirringstirred for 15 minutes
6. customThe substrate was sparged with nitrogen at a moderate rate
7. additionA pre-weighed amount of xylose isomerase-basic magnesium complex containing from 1,000 to 3,000 units of bound isomerase
8. additionwas added
9. customof 60°C
10. customThis yielded a reaction mixture
11. additioncontaining 60 g
12. waitdigested for exactly two hours
13. additionafter enzyme addition
14. filtrationThe material was filtered immediately by vacuum through an 11-cm
15. concentrationthe levulose concentration