Kinetics for isobaric-isothermal inactivation of Bacillus subtilis alpha-amylase

Isobaric-isothermal inactivation of Bacillus subtilis alpha-amylase (BSA, 15 mg/mL in Tris-HCl at pH 8.6) in the pressure range 1-750 MPa and the temperature range 25-85 degrees C could be accurately described by a first-order kinetic model. The kinetic parameters (k, E-a, and V-a) were calculated at different pressure and temperature levels. At reference temperature (40 degrees C) and reference pressure (500 MPa), isobaric-isothermal inactivation was characterized by an E-a value of 74.8 kJ/mol, a V-a value of -23.6 cm(3)/mol, and an inactivation rate constant of 0.0343 min(-1). The influence of 15% glycerol on thermal and pressure-temperature stability of BSA was investigated. In both cases, a stabilizing effect of this additive was found, since the k(ref) value was significantly reduced. Furthermore, a pressure-temperature kinetic diagram, indicating the possible synergistic and antagonistic effects of pressure and temperature on the inactivation of BSA, was constructed. Based on this diagram, a model describing the dependence of the inactivation rate constant on pressure and temperature, in the pressure range 250-750 MPa, was formulated.