| Abstract: | Objective The fermentation medium compositions for doramectin production by mutant strain Streptomyces avermitilis 3D-5 was optimized through response surface methodology (RSM). Methods Firstly, positive effect factors on doramectin production were found by the one-factor-at-a-time method, and then, soybean cake powder, maltodextrin and MgSO4 were screened as the significant factors for doramectin biosynthesis with the Plackett-Burman (P-B) design. Furthermore, the steepest ascent path was applied to investigate the optimal range of the medium composition. Finally, the optimal combination ratio of soybean cake powder, maltodextrin and MgSO4 was determined by the Central composite design (CCD). Results Results showed that the doramectin yield rose up to 589.43mg/L, under the achieved compositions of soybean cake powder 17.30g/L, maltodextrin 77.30g/L, and MgSO4 1.50g/L. The verification experiment showed the doramectin yield was consistent with the model prediction (589.43mg/L), which was 20.37% higher than that of the original medium condition. Conclusion The fermentation process physiological parameters obtained for the strain S. avermitilis 3D-5 in the 5L bioreactor showed that the specific growth rate was signi?cantly enhanced under the optimized medium, and the higher oxygen uptake rate accompanied with higher specific production rate. The specific dormadetin production rate was markedly enhanced in the optimized medium. |
