Thermodynamics and Thermal Inactivation of Endo-β-1,4-Glucanase Produced from Aspergillus niger

Abstract

The limited understanding of the thermal properties of endo-β-1,4-glucanase poses a significant obstacle to its widespread industrial use. This research was designed to explore the thermodynamic and thermal inactivation of endo-β-1,4-glucanase extracted from Aspergillus niger for industrial applications. In this study, grape bagasse was utilized as the carbon source. Endo-β-1,4-glucanase was derived from Aspergillus niger through a submerged fermentation process. Aspergillus niger endo-β-1,4-glucanase was partially purified to the extent of gel filtration chromatography (Sephadex G-100) with a 2.68% yield and a specific activity of 9.21 U/mg after ammonium sulphate precipitation (50% saturation) and dialysis. Endo-β-1,4-glucanase activity reached its optimal at a pH of 5.0. The enzyme exhibited an optimum activity at temperature of 55°C and a maximum thermostability with a half-life of 364.79 min. Thermodynamic parameters showed that the enthalpy of activation of denaturation (∆H) was 26.12, 26.04, 25.99, 25.96, 25.92, 25.87, and 25.79 KJ/mol at 40oC, 50oC, 55oC, 60oC, 65oC, 70oC, and 80oC, respectively. A z-value of 0.014oC was obtained, with an activation energy (Ea) of 28.73 KJ/mol for the denaturation of the enzyme indicating the enzyme's responsiveness to a rise in temperature. The D-value of the enzyme ranged from 291.5 to 1212.1 min. The Gibbs free energy was negative (∆???? > 0) at the temperatures studied, while the entropy change was positive (∆???? < 0). The thermodynamic studies showed the thermal deactivation of the enzyme. These characteristics at the optimum conditions and stability of the enzyme make it a promising enzyme for industrial applications, particularly for bioethanol fermentation.