Thermostability of Aspergillus niger inulinase from sugar beet molasses in the submerged fermentation and determination of its kinetic and thermodynamic parameters.

Inulinases are commonly used for the production of high-fructose syrup, fructooligosaccharides, and inulooligosaccharides and also in the food and pharmaceutical industries. Besides, inulinases are also utilized for the fabrication of various high-added-value products such as bioethanol, lactic acid, citric acid, sugar alcohols, single-cell oils and proteins, 2,3-butanediol, gluconic acid, and butanol. Besides, before using an enzyme in a bioprocess, the determination of its properties is very essential. Therefore, this study evaluated the thermostability (30–80 °C for 0.5–6 h) of Aspergillus niger inulinase produced from sugar beet molasses in the shake flask fermentation and determined its kinetic and thermodynamic features. Based on the thermostability test of inulinase, it was stable at 30 °C and 40 °C and activity retained approximately 78.5% and 21.8% at 50 °C and 60 °C at the end of 6-h incubation time. Besides, half-life and D-value of enzyme reduced with increasing temperature, but increased with increasing incubation time at a fixed temperature. Q₁₀-values were generally below one and reduced with increasing temperature. Nevertheless, inactivation energy and Z-value of inulinase were between 203.8 and 293.2 kJ/mol and between 17.05 and 20.99 °C to varying incubation times. Enthalpy and entropy of inulinase decreased with increasing temperature. The free energy of inulinase was unstable with increasing temperature depending on its inactivation energy. Consequently, inulinase can be used for biocatalytic strategies in various bioprocesses at relatively high temperatures. [ABSTRACT FROM AUTHOR]