| الوصف: |
Background: Xenocoumacin 1 (Xcn 1), a kind of water-soluble antibiotic discovered from the cell-free broth of Xenorhabdus nematophila YL001, has exhibited excellent activity against bacteria, oomycetes and fungi. However, the low yield limits the development and utilization of Xcn1. In order to increase the yield of Xcn1, the fermentation process was optimized in this study. Results: Maltose and proteose peptone were identified as the best carbon and nitrogen sources that significantly affected Xcn1 production using a-factor-at-a-time approach. Response surface methodology was applied to optimize the medium constituents for Xcn1 production by X. nematophila YL001. Higher Xcn1-content (113.65 μg/mL) was obtained after optimizing medium components. The optimal levels of medium components were (g/L): proteose peptone 20.83, maltose 12.74, K2HPO4 3.77. Fermentation conditions, such as initial pH, inoculum size, temperature, rotation speed, liquid volume and the length of fermentation, were also investigated by using a-factor-at-a-time method to get a higher production of Xcn1. X. nematophila YL001 was able to produce higher Xcn1 (153.56 μg/mL) at 25°C, initial pH 7.0, inoculum size 10%, culture medium 75 mL in a 250 mL shake flash with an agitation rate of 150 rpm for 48h. Additionally, kinds, concentrations and adding time of the precursor were also investigated. X. nematophila YL001 was able to produce the highest Xcn1 (173.99 μg/mL) when the arginine was added to the broth with 3 mmol/L at the 12th hour. An overall 243.38% increase in Xcn1 content was obtained as compared with mean observed response at TSB medium.Conclusions: To the best of our knowledge, there are no reports on optimization of fermentation process for Xcn1 production quantified by HPLC. The results show that nutrition, precursors and fermentation conditions had a highly influence on the production of Xcn1 by X. nematophila YL001. The optimized medium and fermentation conditions resulted in a 243.38% increase in Xcn1 production. This work will be helpful for the development of X. nematophila YL001 cultivation process for efficient Xcn1 production and lay a foundation for its industrial production. |
