RESUMO
The effect of cross-link density and amount of porogen on physical properties of the glycidyl methacrylate-pentaerythritol triacrylate (GMA-PETA) copolymer and intern on the immobilization of milk clotting protease from Aspergillus niger MC4 was studied. Almost quantitative expression of the milk clotting protease was achieved with copolymer of 251% cross-link density and generated with 65.4 mL of cyclohexanol as porogen. The pH of 4.0 and 18 h period were the best conditions for binding the milk clotting protease onto the polymer. The immobilized milk clotting protease prepared had an activity of 6000 units/g. The optimum pH and temperature ranges for both soluble and immobilized milk clotting protease preparations were pH 5.6-5.8 and 55-60 degreesC, respectively. Immobilized milk clotting protease was more stable than the soluble enzyme; the half-lives at pH 4.0 and 37 degreesC were 160 and 60 days, respectively. At pH 5.8 and 37 degreesC, the parameters favorable for milk clotting, the immobilized enzyme preparation did not exhibit any aspartic protease activity.
