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-TiO 2 ) and ε-poly- l -lysine-functionalized M-TiO 2 (EPL-M-TiO 2 ) were prepared as carriers for immobilizing SIase. SIase was effectively immobilized on EPL-M-TiO 2 (SI-EPL-M-TiO 2 ) 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-TiO 2 was more stable in pH and thermal tests than SIase immobilized on M-TiO 2 and free SIase. K m of SI-EPL-M-TiO 2 was 204.92   mmol/L, and v max was 45.7   μmol/L/s. Batch catalysis reaction of sucrose by SI-EPL-M-TiO 2 was performed under the optimal conditions. The half-life period of SI-EPL-M-TiO 2 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-TiO 2 has good operational stability. Thus, SI-EPL-M-TiO 2 can be used as a biocatalyst in food industries.