Immobilization of <i>Aspergillus terreus</i> URM4658 inulinase in calcium alginate beads, evaluation of their biochemical characteristics and kinetic/thermodynamic parameters, and application on inulin hydrolysis

The present study aimed to immobilize an inulinase obtained from <i>Aspergillus terreus</i> URM4658 by entrapment in calcium alginate beads. The immobilization process yielded a satisfactory yield (92.72%) using 1.25% sodium alginate and 0.35 M CaCl₂ with a curing time of 90 min. The immobilized enzyme exhibited optimum pH and temperature at 7.0 and 60 °C, respectively, showing an increased affinity for the substrate after the immobilization process, as evidenced by the decrease in <i>K_m</i> compared to its free form. Moreover, the immobilized inulinase demonstrated good thermostability at 50 and 60 °C, as observed from the <i>t</i>_1/2 (649.83-420.84 min) and <i>D</i>-values (2158.67-1398.00 min), respectively. The immobilized biocatalyst also exhibited good reusability, maintaining 92.73% of residual activity after 10 reaction cycles and no loss of activity after 30 days of storage. A continuous inulin hydrolysis operation in a packed bed reactor was performed using the immobilized inulinase, and a maximum release of total reducing sugars and nystose of 3.27 and 0.82 g L^-1, respectively, was observed. The results indicate that an immobilized biocatalyst is a promising alternative for bioprocess involving inulin-rich feedstocks.