Abstract: In order to screen and obtain stable and efficient abiogenousazotobacter, samples were selected from the soil of plant rhizosphere and silt in multiple regions, separated and screened with nitrogen-free medium, and nitrogenase activity was determined by acetylene reduction method. Morphological observation, physiological and biochemical test and 16S rDNA sequence molecular identification were made. Furthermore, the growth conditions were optimized through a combination of single factor and response surface test. The results showed that a strain of abiogenousazotobacter with nitrogenase activity of 140.14 nmol C2H4/mg·protein·hr was screened from the soil of the corn rhizosphere in Shuozhou, Shanxi Province. It was identified as Azotobacter and named Azotobacter sp. strain C-5-2; the optimal conditions for the growth of the strain were sucrose concentration 10 g/L, rotation speed 148 r/min, temperature 32 ℃ and initial pH 9.0.

Key words: abiogenousazotobacter, screening, growth conditions, response surface optimization