Fig. 3
(a) thermal stability, and (b) pH stability (at 60 °C) of A. niger NRC114 purified α-galactosidase enzyme. Thermal stability was checked by incubating the enzyme (25.39 U/mL) at 50, 60, 65, and 70 °C for 120 min in a citrate phosphate buffer (50 mM, pH 3.5) and assayed periodically for its remaining activity under the standard conditions. For pH stability, the enzyme was incubated in a range of pH levels from pH 3.0 to 7.0 for 2 h at 60 °C and evaluated for its residual activity under typical circumstances. The vertical bars show the standard deviation values, and each value reflects the mean of three replicate measurements (c) Lineweaver–Burk plot of the reciprocal of initial velocities and pNP-α-D-Gal concentrations. Km and Vmax values were determined using the Lineweaver–Burk plot technique in GraphPad Prism version 6.01, and the experiments were performed in triplicate