Figure 3

Enzymatic properties of the purified phytase. (a) Effect of temperature on the activity of the phytase. (b) Effect of pH on the activity of the phytase. (c) The thermal stability of the phytase. (d) pH stability of the phytase. The optimal temperatures for the activity of phytase were investigated by incubating 0.5 ml reaction mixture for 10 min. The reaction mixtures contained 0.2 ml of 20 mM phosphate buffer (pH 7.0), 0.2 ml sodium phytate as the substrate and 0.1 ml of the phytase, and the temperature range examined was 20–80°C. The effect of pH on the activity of the phytase was studied using 0.5 ml reaction mixtures containing 0.2 ml of the buffer and 0.2 ml sodium phytate as the substrate at 55°C for 10 min. Buffers used were: 0.1 M glycin − HCl buffer, pH 3.0; 0.1 M acetic acid buffer, pH 4.0 − 5.0; 0.1 M Tris–HCl buffer, pH 6.0 − 9.0; and 0.1 M glycine − NaOH buffer, pH 10.0 − 11.0. To study the stability of the phytase, aliquots of the enzyme solutions were subject to different temperatures and pHs for 30 min. Temperatures used were 37, 55, 80 and 90°C. pHs used were 4, 6, 7, 8 and 9. The residual activity of the phytase was detected once every 5 min, and the relative activity of the phytase was calculated. The control sample is phytase at 4°C and pH 7.0, and its activity is defined as 100%.