An innovative method for immobilizing sucrose isomerase on ε-poly-L-lysine modified mesoporous TiO₂

Sucrose isomerase (SIase) is the key enzyme in the enzymatic synthesis of isomaltulose. Mesoporous titanium dioxide (M-TiO₂) and ε-poly-L-lysine-functionalized M-TiO₂ (EPL-M-TiO₂) were prepared as carriers for immobilizing SIase. SIase was effectively immobilized on EPL-M-TiO₂ (SI-EPL-M-TiO₂) with an enzyme activity of 39.41 U/g, and the enzymatic activity recovery rate up to 93.26%. The optimal pH and temperature of immobilized SIase were 6.0 and 30 °C, respectively. SI-EPL-M-TiO₂ was more stable in pH and thermal tests than SIase immobilized on M-TiO₂ and free SIase. K_m of SI-EPL-M-TiO₂ was 204.92 mmol/L, and ν_max was 45.7 μmol/L/s. Batch catalysis reaction of sucrose by SI-EPL-M-TiO₂ was performed under the optimal conditions. The half-life period of SI-EPL-M-TiO₂ under continuous reaction was 114 h, and the conversion rate of sucrose after 16 batches consistently remained at around 95%, which indicates that SI-EPL-M-TiO₂ has good operational stability. Thus, SI-EPL-M-TiO₂ can be used as a biocatalyst in food industries.