Thermal inactivation kinetics and thermodynamic properties of immobilised Aspergillus niger pectinase in rigid polyurethane foam

The present work was performed in order to investigate the effect of in situ immobilisation of commercial Aspergillus niger pectinase in rigid polyurethane foam (RFPU) on thermal stability. Pectinase (liquid, lyophilised, and immobilised) was incubated from 50 to 80 degrees C. Residual activity data were fit to various kinetic models, which were rigorously evaluated by statistical and physical criteria. The first-order model provided the best fit to describe the thermal deactivation of pectinase. Immobilised pectinase exhibited higher thermal stability, presenting lower K-d-values (0.0015-0.0157 h(-1)) and higher half-life (t(1/2); 456.89-44.01 h), D (1517.86-146.22 h) and Z (29.85 degrees C) values. Thermodynamic parameters (Delta G*, Delta H* and Delta S*) corroborate that immobilised pectinase is thermodynamically more stable if compared to its free and non-immobilised forms (liquid and lyophilized), suggesting that their functionally active conformation was more conserved during the heat treatment. The feasibility of immobilisation is presented towards improving the thermal stability and the resistance to irreversible deactivation of pectinase. (C) All Rights Reserved