Abstract:The high-yielding strain of sisomicin was selected by protoplast normal pressure and room temperature plasma mutagenesis. A high-yielding strain I4-10 was obtained through mutagenesis and the biological titer of sisomicin reached 1 389 U/mL, which was 35.4% higher than the original strain. By optimizing the carbon source and nitrogen source of the high-yielding strain I4-10, it was determined that the soluble starch and beef meal were the most suitable carbon and nitrogen sources for the mutant strain I4-10. The response surface method was further used to optimize the fermentation medium. Results showed that the mass concentrations of soybean meal and DL-methionine were significant influencing factors, and the optimal addition concentrations were 32.78 g/L and 1.75 g/L, respectively. Under this optimal condition, the biological titer of sisomicin was increased to 1 849 U/mL, which was 80% higher compared to the original strain. Finally, the authors compared the transcription level of the key enzymes related to the metabolic pathway of sisomicin, the growth of the high-yielding mutant strain and the strain in the starting bacteria, and preliminarily analyzed the high production mechanism of sisomicin by the mutant strain I4-10.
