Abstract: In order to obtain SOD-producing strains, diluted plate method was used to isolate strains from soil. Non-denaturing gel electrophoresis and NBT staining were applied to identify SOD. The types of SOD were analyzed by inhibition test. Homological analysis was conducted according to physiological and biochemical characteristics as well as 16S rDNA sequence analysis. Furthermore, the effects of carbon source, nitrogen source, carbon/nitrogen ratio, inoculation amount, and medium volume in a 250 mL flask on the yield of SOD were investigated. The results showed that among 10 strain isolates, Lshm-3 was found to have higher ability to produce SOD. The SOD produced by the strain Lshm-3 was sensitive to chloroform-ethanol and insensitive to H2O2 and therefore could be identified as Mn-SOD. NBT staining revealed that this enzyme was a SOD isozyme. The strain Lshm-3 was identified as a member of the genus SerratiaBizio. Its fermentation conditions were optimized to be using maizena as the carbon source, using peptone as the nitrogen source, carbon/nitrogen ratio of 4:1, inoculation amount of 8%, and medium volume in a 250 mL flask of 70 mL.

Key words: isolation, SOD-producing strain, identification, optimization