Figure 3.

Effect of temperature on the enzyme activity at pH 6.0. Fe₃O₄-CS-immobilized enzyme (0.2 g), Fe₃O₄-CS-THP-immobilized enzyme (0.2 g) or the free enzyme (1 mL) was added to 100 mL of 5% (w·v⁻¹) lactose at pH 6.0 in a 500 mL Erlenmeyer flask and incubated at various temperatures from 20 to 90 °C in an orbital shaker bath at 200 rpm for 10 min. The relative activity was determined by measuring the production of glucose. The data are averaged from three samples. (●) Fe₃O₄-CS-immobilized enzyme; (○) Fe₃O₄-CS-THP-immobilized enzyme; (▼) free enzyme.