Long Term Storage at Room Temperature

Silica gel monoliths with immobilized CK were prepared and stored in near-neutral pH buffer solution at room temperature for as long as 6 mo. As a comparison, CK in liquid buffer was also stored under the same conditions. Figure 7 shows the relative activity of the enzyme in the sol-gel matrix compared with in liquid buffer. The activity in both the sol-gel monoliths and in solution was normalized to the initial rate. As seen in Fig. 7, the encapsulated enzyme retained 90% of its activity after about 5 mo. Thereafter, the activity began to decline and decreased to 50% of its maximum value after 6 mo. By contrast, the activity of CK in liquid buffer dropped to approx 50% of its original activity after only 10 d of storage at room temperature.

Fig. 7. Relative activity as a function of time for CK when stored at room temperature in pH 7.0 HEPES buffer solution (•) and in sol-gel silica (■) shows that the enzyme had enhanced storage stability as a result of sol-gel encapsulation. The maximum activities per milligram of enzyme for the solution and sol-gel were 0.2 and 7 x 10-5, respectively. (Reproduced from Ref. 17 with permission.)

Fig. 7. Relative activity as a function of time for CK when stored at room temperature in pH 7.0 HEPES buffer solution (•) and in sol-gel silica (■) shows that the enzyme had enhanced storage stability as a result of sol-gel encapsulation. The maximum activities per milligram of enzyme for the solution and sol-gel were 0.2 and 7 x 10-5, respectively. (Reproduced from Ref. 17 with permission.)

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