Heterologous expression and characterization of multi-resistant manganese superoxide dismutase from Thermus aquaticus in Escherichiacoli.

This study describes the heterologous expression and stability profiling of a manganese superoxide dismutase from Thermus aquaticus (TaqMn-SOD). Codon-optimized TaqMn-SOD fused with a C-terminal 6His tag was expressed in Escherichia coli. The apoenzyme (ApoTaqMn-SOD) was successfully recovered and purified under optimized induction conditions followed by post-lysis thermal treatment (85 °C for 90 min), affording a yield of >100 mg of purified protein per liter of culture. The purified TaqMn-SOD exhibits a specific activity of about 3000 U/mg and exceptional stability profiles: retaining full activity at 85 °C for 4 h; maintaining >56% activity across a broad pH range of 3.0-12.0; tolerating ethanol concentrations up to 40%, preserving >80% activity after 48 h and 50-80% activity after 90 d in 5-20% ethanol. Moreover, its activity was not significantly affected by various divalent metal ions (excepting Fe2+), organic solvents, detergents, denaturants, or the chelating agent EDTA, with n-hexane enhancing activity by 47%. The enzyme was partially inactivated (47%) in simulated gastric fluid for 10 min, but remained stable in simulated intestinal fluid and water. These results suggest that TaqMn-SOD holds potential for applications in high-temperature food processing, thermally-stable cosmetic manufacturing, agricultural protection, and pharmaceutical formulations requiring stability under extreme conditions.