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The use of enzymes in organic solvents has biotechnological and industrial importance. Organic solvents can decrease the stability of enzymes that is a challenge for the use of enzymes in organic media. There are several approaches such as protein engineering, chemical modification, and use of additives for stabilization of enzymes in organic solvents. In this study, activity and stability of trypsin were investigated in the presence of different organic solvents. Then the effect of sucrose on the stability of the enzyme was investigated in the absence and prescence of solvents. The result showed that the activity and stability of trypsin were decreased in the presence of organic solvents. DMF had a lowest effect on the activity and stability of the enzyme. The use of sucrose increased the stability of trypsin in the presence of organic solvents. The stabilization effect of sucrose in the presence of DMF was more than other solvents. Consequently, a mixture of DMF and sucrose is proposed for the use of trypsin in industrial applications.

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Uricase or urate oxidase is an enzyme that converts uric acid (with low solubility) to 5-hydroxyisourate and finally to allantoin. The possibility of developing some diseases like gout and kidney stones will be increased in high levels of uric acid. Thus, uricase can be used as drug enzyme to reduce uric acid levels in the blood. The low stability of proteins (such as drug enzymes) is a challenge in the use of them. There are several approaches such as use of additives for protein stabilization. In this study, E. Coli BL21 (DE3) was transformed by pET28a (+) vector carrying Aspergillus flavus uricase gene. The recombinant protein was expressed and then purified by a Ni-NTA agarose chromatography column. After purification, the thermal stability of the purified enzyme was evaluated and then it stabilized by additives. The results showed that enzyme is active and purified very well. Thermal stability results indicated that uricase maintains its stability up to 20°C and then loses its stability. The half-life of enzyme was 30minutes at 40 °. The results of enzyme stabilization by 20% (v/w) concentration of glucose and sorbitol as well as by 20 % (v/v) of glycerol showed that glucose had the most stabilization effect on the uricase among the additives. The stability (half life) of enzyme was increased more than two times in the presence of glucose. Finally, we conclude that additives like glucose which increase surface tension have the most stabilization effect on the uricase enzyme stability.