Heterologous expression and enzymatic properties of catalase from Bacillus sonorensis s262

Abstract:

[Background] The catalase produced by Bacillus sonorensis s262 has the ability to degrade aflatoxin B₁ (AFB₁).[Objective] To express Bacillus sonorensis s262 peroxidase in Escherichia coli, optimize the expression conditions, and determine the enzymatic properties. [Methods] The catalase gene katA was ligated into the pET28a(+) vector to construct the recombinant expression plasmid pET28a-katA, which was then transformed into E. coli BL21(DE3) competent cells. Furthermore, the expression conditions including IPTG concentration, the induction temperature, and the induction time of the recombinant enzyme were optimized. Ni-NTA Sefinose^TM resin was used to purify the recombinant enzyme. The optimal reaction temperature and thermal stability, the optimal pH and pH stability, and the effects of metal ions on the enzyme activity were determined, and the kinetics of the recombinant enzyme was analyzed by double-reciprocal plotting. The degradation rate of AFB₁ by the recombinant catalase was measured by high performance liquid chromatography. [Results] The recombinant expression plasmid pET28a-katA proved to be successfully constructed by double digestion (BamH Ⅰ and Hind Ⅲ) and sequencing. The molecular weight of the purified recombinant enzyme ranged from 55 kDa. The expression conditions in E. coli were optimized as follows: induction with 0.8 mmol/L IPTG at 25 ℃ for 10 h. The kinetic parameters V_max and K_m were (760.17±19.61) mmol/(min·L) and (63.73±3.87) mmol/L, respectively, at the optimal catalytic temperature of 50 °C and optimal pH 7.0. In addition, 0.1 mmol/L Fe²⁺, Zn²⁺, and Cu²⁺ increased the enzyme activity by 40%, 8%, and 12%, respectively, while 0.1 mmol/L K⁺ decreased the enzyme activity by 39%. The degradation rate of AFB₁ by the recombinant enzyme was 61.44%. [Conclusion] We successfully expressed and purified the catalase of B. sonorensis in E. coli, laying a foundation for the industrial production and application of catalase.