Optimization of Medium Composition for Expression of Recombinant Sucrose Phosphorylase and Effect of Chemical Reagents on Enzyme Activity

In order to improve the expression level of recombinant sucrose phosphorylase, the effects of different carbon sources, nitrogen sources, protectants and metal ions on the expression of recombinant sucrose phosphorylase in Escherichia coli was studied by single factor test, then the optimal composition of recombinant sucrose phosphorylase expression medium was determined by orthogonal test. In addition, the effects of different chemical reagents and metal ions on the stability of recombinant sucrose phosphorylase were investigated.The results showed that vitamin C and FeCl₂ significantly (P<0.01) inhibited the protein expression, and Cu²⁺ and Zn²⁺ completely killed the microorganisms. On the contrary, starch, K⁺ and Mg²⁺ could promote the expression of recombinant sucrose phosphorylase, and the synergistic effect could greatly improve the expression efficiency of recombinant sucrose phosphorylase. The total enzyme activity of optimal combination, with 0.5% starch, 0.1% K⁺ and 0.05% Mg²⁺ in 50 mL LB medium, was 1207.83 U, which was increased by 3.6 -fold. The results showed that 10 mmol/L Fe²⁺, 10 mmol/L Mg²⁺, 1% bovine serum protein and 0.1% Tween 80 could increase the enzyme activity and stability of sucrose phosphorylase in a certain extent.