Application of the new method to determine the activation energies and optimum temperatures of inulin hydrolysis by exo-inulinases Aspergillus niger

Abstract

Inulinases catalyze the hydrolysis of inulin to obtain fructose with a yield of about 90–95%. Inulin is a reserve carbohydrate in plant tubers like Jerusalem artichoke, chicory, garlic and onion, leek, rye, barley, dandelion, burdock, banana. The paper presents a comparative analysis to determine the optimum temperatures and the activation energies for various origin exo-inulinases from Aspergillus niger. The parameters were estimated based on the literature of the activity curves versus temperature for hydrolysis of inulin. It was assumed that both the hydrolysis reaction process and the deactivation process of exo-inulinase were first-order reactions by the enzyme concentration. The governing equations are formulated including the activation energy of the deactivation process and temperature effects. A mathematical model describing the effect of temperature on exo-inulinases from Aspergillus niger activity was used. Based on the comparison analysis, values of the activation energies $$E_{\mathrm{a}}$$ were in the range from $${25.20 \pm 2.92}$$ to $${60.95 \pm 8.30}\,\hbox {kJ}\,\hbox {mol}^{-1}$$ , the deactivation energies $$E_{\mathrm{d}}$$ were in the range from $${80.86 \pm 3.59}$$ to $${268.66 \pm 24.06}\,\hbox {kJ}\,\hbox {mol}^{-1}$$ and the optimum temperature $$T_{\mathrm{opt}}$$ was obtained in the range from $${325.25 \pm 0.41}$$ to $${337.35 \pm 0.70\,\hbox {K}}$$ .