Screening of fermentation medium for herbicidal active strain HZ-011 and optimization of its conditions

【Objective】 Todetermine the ratio of various factors of the fermentation medium and the optimal fermentation conditions of strain HZ-011 that has herbicidal effect on weeds, andprovide theoretical basis for development of HZ-011 herbicide and application in farmland.【Method】 The basic medium for the growth of strain HZ-011 was selected by solid medium with the goal of spore production. Single factor experiment was used to optimize the fermentation medium and fermentation conditions of strain HZ-011. The liquid medium composition and ratio of strain HZ-011 were optimized by using the principle of central composite design(CCD). The interaction between the components of the medium was analyzed by response surface methodology. The pathogenicity of potted weeds(Chenopodium album, Amaranthus retroflexus, Elsholtzia densa and Malva crispa) was tested with HZ-011 fermentation broth.【Result】 After optimization, the optimal proportion of culture medium of strain HZ-011 was sucrose 48.744 g/L, peptone 15.626 g/L, NaCl 0.214 g/L and K₂ HPO₄0.428 g/L. The optimum fermentation conditions were p H 7, temperature 25 ℃, culture time 5 days, liquid loading 180 ml and rotating speed 180 r/min. The results of pot experiment showed that strain HZ-011 killed all C. album and A. retroflexus, and the pathogenicity of E. densa was 75%, then the pathogenic rate of winter sunflower was 40%.【Conclusion】 The optimized medium increased the spore production of strain HZ-011, which lays a foundation for the application of the strain in the biological control of farmland weeds.