Thermal stability of two xylanases from Macrotermes subhyalinus little soldier: kinetic and thermodynamic analysis | IJB
Description
The knowledge on thermal inactivation kinetics of enzymes is necessary to allow their adequate utilization as natural biopreservatives in the food industry and technology applications. In this work, the kinetics of thermal inactivation was studied for the previously purified and characterized xylanases Xyl1 and Xyl2 from Macrotermes subhyalinus little soldier. Samples of xylanases were treated at different time-temperature combinations in the range of 5-60 min at 50-65°C and the kinetic and thermodynamic parameters for xylanases were calculated. The inactivation kinetic follows a first-order reaction with k-values between 0.0192 ± 0.0002 to 0.0405 ± 0.0003 and 0.0119 ± 0.0005 to 0.0418 ± 0.0004 min-1 for Xyl1 and Xyl2, respectively. Activation energy (Ea) and Z-values were estimated to 48.08 ± 1.84 kJ mol-1 and 43.47 ± 3.02°C for Xyl1, 75.52 ± 3.52 kJ.mol-1 and 27.77 ± 1.87°C for Xyl2. The catalytic reactions of both xylanases are endothermic due to positive enthalpy. The high value obtained for the variation in enthalpy of activation indicates that a high amount of energy is required to initiate denaturation, probably due to the molecular conformation of xylanases. All results suggest that both xylanases are relatively resistant to long heat treatments up to 50°C.