초록
<P><B>Abstract</B></P> <P>The kinetics and thermodynamics of <I>Aspergillus aculeatus</I> pectinase, either free or immobilized in alginate beads, were investigated. Pectinase immobilization ensured an enzyme immobilization yield of 59.71%. The irreversible denaturation of pectinase in both preparations was evaluated at temperatures ranging from 30 to 60 °C. When temperature was raised, the first-order thermal denaturation constant increased from 0.0011 to 0.0231 min<SUP>−1</SUP> for the free enzyme and from 0.0017 to 0.0700 min<SUP>−1</SUP> for the immobilized one, respectively. The results of residual activity tests enabled us to estimate, for denaturation of both free and immobilized pectinase, the activation energy (<I>E</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> = 85.1 and 101.6 kJ·mol<SUP>−1</SUP>), enthalpy (82.59 ≤ <I>ΔH</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ 82.34 kJ·mol<SUP>−1</SUP> and 99.11 ≤ <I>ΔH</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ 98.86 kJ·mol<SUP>−1</SUP>), entropy (−63.26 ≤ <I>ΔS</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ −63.85 J·mol<SUP>−1</SUP>·K<SUP>−1</SUP> and −5.50 ≤ <I>ΔS</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ −5.23 J·mol<SUP>−1</SUP>·K<SUP>−1</SUP>) and Gibbs free energy (101.8 ≤ <I>ΔG</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ 104.7 kJ·mol<SUP>−1</SUP> and 100.6 ≤ <I>ΔG</I> <SUP> <I>⁎</I> </SUP> <SUB> <I>d</I> </SUB> ≤ 102.0 kJ·mol<SUP>−1</SUP>). The integral activity of a continuous system using the free and immobilized enzyme was also predicted, whose results indicated a satisfactory enzyme long-term thermostability in both preparations at temperatures commonly used to clarify juice. These results suggest that both free and immobilized pectinase from <I>A. aculeatus</I> may be profitably exploited in future food industrial applications, with special concern to the immobilized enzyme because of its reusability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pectinase immobilized in alginate beads has good thermostability. </LI> <LI> Free and immobilized pectinase activity and thermoinactivation are investigated. </LI> <LI> Free and immobilized pectinase are stable at temperatures used for juice processing. </LI> <LI> Immobilization increases the thermostability of pectinase from <I>A. aculeatus</I>. </LI> </UL> </P>