Kinetics and thermodynamics of keratin degradation by partially purified and encapsulated keratinase from Bacillus vallismortis DSM11031

摘要

In this study, keratinase was partially purified by thermal precipitation then, entrapped and cross linking via glutaraldehyde into Na-Alginate, and examined the properties of the immobilized enzyme. The molecular weight of the enzyme was found as 63 kDa. Immobilization was achieved with 83.76 yield. Reusability of immobilized enzyme was determined as 12 times with 90 residual activity. Maximum keratinolitic activity time was measured as 40 minutes. Optimum pH for free keratinase was 8.0, for immobilized keratinase was 6.0, however, optimum temperature did not change both free and immobilized keratinase. The Michaelis-Menten constant (K-m) were found as 2.5 x 10(-3) M and 0.011 M for free and immobilized keratinase, respectively. The maximum reaction rate (V-max) for the free and immobilized keratinase was calculated as 83.33 U mL(-1 )min(-1) and 12.5 10.83 U mL(-1 )min(-1), respectively. Furthermore, The turnover number (k(cat)) and catalytic performance (k(cat)/K-m) of enzymes were 58.8 min(-1) and 1.96 x 104 min(-1)M(-1) for the free enzyme, 9.80 min(-1) and 8.91 x 102 min(-1)M(-1) for the encapsulated enzyme, respectively. Thermodynamic parameters of free enzyme; Delta G(#): 6.62 x 104 kJ mol(-1); Delta G(#) (E-T): -2.57 x 104 kJ mol(-1); Delta G(#) (ES): -1.51 x 104 kJ mol(-1); Delta H-#: -2.60 x 103 kJ mol(-1); Delta S-#: -2.20 x 102 kJ mol(-1) K-1 and the thermodynamic parameters of the encapsulated enzyme Delta G(#): 7.08 x 104 kJ mol(-1); Delta G(#) (E-T): -1.77 x 104 kJ mol(-1); Delta G(#) (ES): -1.17 x 104 kJ mol(-1); Delta H-#: -2.60 x 103 kJ mol(-1); Delta S-#: -2.35 x 102 kJ mol(-1) K-1.