Thermal inactivation kinetics of Aspergillus oryzae β-galactosidase in concentrated lactose solution

Abstract

Thermal inactivation of a commercial β-galactosidase from Aspergillus oryzae in a 300 g/L lactose solution was studied in the temperature range of 65-75 °C. Lactose exhibited a stabilisation effect when similar inactivation rates as those in lactose solution were observed in a lactose-free solution at temperatures lower by 5 °C. Inactivation process in the lactose solution was biphasic. A kinetic model based on the Lumry-Eyring mechanism was proposed and successfully verifi ed. Estimated activation energy values were very different. Rather high activation energy values of the forward reactions were responsible for both the signifi cant change of rate constants and the rate-controlling reaction with temperature. For these two reasons, an increase of the operational lifetime of the enzyme from 7 days at 60 °C to 580 days at 55 °C was predicted.

Boosting the stability of β-galactosidase immobilized onto soy-protein isolate-glutaraldehyde-functionalized carrageenan beads

“…The specific and robust binding amid the substrates and the native conformation of their enzyme reduces the possibility of thermal denaturation presumably owing to conformational tightening (Lejeune et al 2001 ). Furthermore, the βGL substrate, lactose, was formerly reported to boost the thermal stability of altered βGLs (Illeová and Polakovič 2018 ; Warmerdam et al 2013 ). Thus, the 56 °C thermal incubation of the iβGL was accomplished while placing the iβGL in a lactose solution.…”