Partial purification and characterization of Aspergillus niger inulinase produced from sugar-beet molasses in the shaking incubator and stirred-tank bioreactors.

The objectives of this study were to purify Aspergillus niger inulinase produced from sugar-beet molasses in the shaking incubator (100 mL) and stirred-tank bioreactors (5-L and 30-L) by using some downstream processes and to determine enzyme kinetics and characterization. The results showed that the best centrifuge-time combination was 16,873 ×g-5 min with the purification coefficient of 1.4. Besides, with the ultrafiltration process, the inulinase activities yielded using the shaking incubator, pH-controlled/uncontrolled small-scale bioreactors, and large-scale bioreactor were increased from 1101.3, 2079.2, 1561.3, and 787.5 U/mL to 12,065.2, 21,789.0, 11,296.9, and 2948.1 U/mL with purification coefficients of 5.33, 1.38, 1.46, and 1.67, respectively. Additionally, for the inulinase from shaking incubator and pH-uncontrolled bioreactor, the values of Km for inulin and sucrose were 17.8 and 49.4 mg/mL and 28.8 and 25.9 mg/mL, respectively. As the enzyme amount added to the substrate increased, the activity also increased. Mn2+ is the activator of the enzyme, and Cu2+ and Ag+ are inhibitors of the enzyme. The molecular weight of inulinase has been determined to be between 60 and 70 kDa. Consequently, this study ensures valuable and significant information about the purification and characterization of inulinase for industrial implementations.