Enhancement in stability and reusability: Immobilization and characterization of inulin fructotransferase from Paenarthrobacter aurescens QL1.001 in calcium alginate microcapsules

Inulin fructotransferase (IFTase), a microbial enzyme , efficiently catalyzes the conversion of inulin into difructose anhydride Ⅲ (DFA Ⅲ). However, the poor stability and reusability of IFTase limits its industrial application. To overcome this challenge, IFTase from Paenarthrobacter aurescens QL1.001 was immobilized in calcium alginate microcapsules using the method of emulsification/internal gelation in this work. A systematic optimization of the microcapsule preparation parameters was conducted using a single-factor experimental design, resulting in an optimal formulation: 1.5% sodium alginate concentration, a molar ratio of calcium carbonate to sodium alginate (Ca/Alg) of 0.33, a molar ratio of glacial acetic acid to calcium carbonate (acid/Ca) of 5, the enzyme amount of 4 mg, and ferroferric oxide (Fe 3 O 4 ) amount of 10 mg. Furthermore, the particle size of the microcapsules was regulated via adjusting the stirring speed, revealing that as the stirring speed increased, the particle size decreased gradually, while the recovery of immobilized enzyme remained relatively stable. Compared to the free enzyme, IFTase immobilized within calcium alginate microcapsules demonstrated significantly enhanced pH and thermal stability . The immobilized enzyme retained 71.77% of its initial enzyme activity after incubation at 70 °C for 3 h. This immobilized enzyme also exhibited remarkable storage stability and reusability, retaining 14.83% of its initial activity after eight consecutive uses. In summary, the proposed calcium alginate microcapsule immobilization technique for IFTase significantly improved enzyme stability and reusability, offering a practical approach for the industrial production of DFA III. • Inulin fructotransferase was immobilized in calcium alginate microcapsules. • The formula of calcium alginate microcapsules was optimized. • Microcapsule particle size decreased with increasing stirring speed. • The thermal and pH stability of the immobilized IFTase were significantly improved. • The immobilized IFTase exhibited excellent storage stability and good reusability.