Construction of a New Genetic Engineering Bacterium for Preparation of Superoxide Dismutase with High Productivity

Abstract

A new Mn-SOD gene encoding 202 amino acids was cloned from genomic DNA of Bacillus subtilis ATCC 9372 for construction of a genetic engineering bacterium to produce SOD. Its phylogenetic relationships with other Bacillus spp. revealed that this predicted protein is most closely related to B. atrophaeus NRS-213 (AY197616) and B. subtilis 168. This gene was inserted into expression plasmid pET28a and first successfully expressed in E. coli BL21. The SOD was expressed accounted for approximately 45.6% of total bacterial protein. The activity of the SOD was 2553.211 U/mg, the enzyme showed maximum activity at about pH 8.0 and relatively stable from pH 6.0 to 11.0. This SOD had a good thermal stability with >75% retaining of the relative enzymatic activity after incubation at 50 °C for 90 min. This study demonstrated that a new genetic engineering bacterium to produce SOD with high productivity has been successfully constructed.