| Summary: | Inulinases are enzymes involved in the hydrolysis of inulin, which can be used in the food industry to produce high-fructose syrups and fructo-oligosaccharides. For this purpose, different <i>Aspergillus</i> strains and substrates were tested for inulinase production by solid-state fermentation, among which <i>Aspergillus terreus</i> URM4658 grown on wheat bran showed the highest activity (15.08 U mL<sup>−1</sup>). The inulinase produced by this strain exhibited optimum activity at 60 °C and pH 4.0. A detailed kinetic/thermodynamic study was performed on the inulin hydrolysis reaction and enzyme thermal inactivation. Inulinase was shown to have a high affinity for substrate evidenced by very-low Michaelis constant values (0.78–2.02 mM), which together with a low activation energy (19.59 kJ mol<sup>−1</sup>), indicates good enzyme catalytic potential. Moreover, its long half-life (<i>t</i><sub>1/2</sub> = 519.86 min) and very high <i>D</i>-value (1726.94 min) at 60 °C suggested great thermostability, which was confirmed by the thermodynamic parameters of its thermal denaturation, namely the activation energy of thermal denaturation (<i>E*<sub>d</sub></i> = 182.18 kJ mol<sup>−1</sup>) and Gibbs free energy (106.18 ≤ Δ<i>G</i>*<sub>d</sub> ≤ 111.56 kJ mol<sup>−1</sup>). These results indicate that <i>A. terreus</i> URM4658 inulinase is a promising and efficient biocatalyst, which could be fruitfully exploited in long-term industrial applications.
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