Immobilization of pectinase on the glass bead using polyaldehyde kefiran as a new safe cross-linker and its effect on the activity and kinetic parameters

•Pectinase was immobilized on glass bead by oxidized kefiran as a new cross-linker.•The best immobilized enzyme activity was obtained at temperature 50 °C and pH 5.5.•Thermal and pH stability of immobilized enzyme was higher than free enzyme.•Immobilized pectinase had a great reusability.•SEM and AFM were used to confirm the immobilization of pectinase on glass beads. For the first time, polyaldehyde kefiran was applied to immobilize the pectinase on the glass bead and the finding was compared with free enzyme. Polyaldehyde kefiran, produced by periodate oxidation of kefiran, showed an aldehyde content of 23.6 ± 0.9% that was confirmed by FTIR. The results showed although the optimum temperature (50 °C) was not changed by immobilization, the optimum pH was shifted from 5.0 to 5.5. In optimal conditions, the specific activity of the free and immobilized pectinase was 2.93 ± 0.13 and 1.87 ± 0.24 unit/mg, respectively. Also, the immobilized pectinase had a higher thermal and pH stability than free enzyme. Km and Vmax of the immobilized pectinase were higher and lower than the free enzyme, respectively. In addition, SEM and AFM images illustrated a completely non-uniform surface after enzyme immobilization on the glass bead, which seemed to be related to the polyaldehyde kefiran strands.