The Effect of 1-Ethyl-3-methylimidazolium Acetate Ionic Liquid on the Structural and Functional Features of a Representative α-amylase

Introduction: α-Amylases catalyze the starch hydrolysis reaction and are widely used in starch processing industries. Despite the high demand for the use of α-amylase in various industries, most α-amylases do not have the required functional characteristics such as proper activity, temperature and pH compatibility, as well as temperature stability. In this regard, ionic liquids are widely used today as co-solvents to improve enzymes activity, stability, and selectivity. Materials and Methods: Activity, optimum temperature, optimum pH, and thermal stability of B. subtilis α-amylase were investigated in the presence of 1-ethyl-3-methylimidazolium acetate. Structural changes in the presence of [EMIm][Ac] were examined using intrinsic fluorescence spectroscopy. Results: The activity of α-amylase and Vm increased in the presence of 0.4 M of [EMIm][Ac] while Km decreased. The optimum temperature and pH did not change in the presence of [EMIm][Ac] compared to its absence. At 40 and 50 °C, the inactivation rate of α-amylase in the presence of both concentrations of 0.4 and 1 M of [EMIm][Ac] is the same as in its absence. However, the rate of inactivation at 60 and 70 °C is higher than that in the absence of [EMIm][Ac]. The results of intrinsic fluorescence spectroscopy confirmed the structural changes in the presence of [EMIm][AC]. Conclusion: [EMIm][Ac] can be used to increase the activity of B. subtilis α-amylase without affecting the optimal temperature and pH parameters. Moreover, [EMIm][Ac] relatively improves the thermal stability of the α-amylase.