Thermalstabilization of chitinolytic enzymes of Pantoea dispersa

The thermodynamic deactivation kinetics, ΔH*, ΔS*, E and ΔG* were used to understand the stability behaviour of the novel chitinases (I–III) of the marine isolate Pantoea dispersa in a range of salts and varying pH conditions (pH 4–9). The deactivation rate decreased with increasing half-life of chitinase I–III in the presence of salts at 30–60 °C with the following effect on the order of stability evident NaCl > KH2PO4 > KBr > NH4NO3 > KNO3 > MgSO4·7H2O > CaCl2. With increasing pH the deactivation rate decreased whilst the half-life of chitinase I–III increased. This lead to increased stability at high pH's with the following order of stability evident 9 ≥ 8 > 7 > 6 > 5 > 4 at 30–60 °C. With increasing pH's and addition of each salt ΔH* of chitinase I–III increased whilst deactivation energy decreased. Furthermore, ΔS* was found to be comparatively lower than untreated chitinase I–III. The free energy of chitinase I–III decreased with increasing pH and different salts in the same order as described above. The greater stability of chitinase I (t1/2: 270, 225, 185 and 135 min), chitinase II (t1/2: 225, 210, 195 and 135 min) and chitinase III (t1/2: 210, 150, 120 and 105 min) at 30–60 °C respectively were observed at pH 8. With the addition of NaCl, the following stabilities of chitinase I (t1/2: 270, 225, 185 and 135), chitinase II (t1/2: 225, 210, 195 and 135) and chitinase III (t1/2: 210, 150, 120 and 105) at 30–60 °C respectively were observed which is greater than the chitinase of Trichoderma harzianum a recognised commercial biocontrol agent.