The Optimization of Fermentation Conditions for Antifungal MetaboliteProduction with Streptomyces hygroscopicus A03

[Aims]Streptomyces hygroscopicus A03 is an antagonistic strain isolated by this research group.In previous studies,the active metabolite of the strain presented a significant inhibitory effect against many phytopathogenic fungi.In order to develop an efficient fermentation process for producing antifungal substances with Streptomyces hygroscopicus A03 and provide technical parameters for the further scale up of the process,the medium components and culture conditions were optimized with methods of orthogonal design and mono-factor test in this paper.[Results] The following optimal formula of liquid production medium was obtained: glucose 5 g/L,soluble starch 5 g/L,soybean meal 10 g/L,KH2PO4 0.5 g/L,CaCO3 1 g/L and MgSO4·7H2O 0.1 g/L.The suitable culture conditions were as follows: the liquid seed was cultured for 40 hours,the fermentation was carried out in 500 mL erlenmeyer flask with 80 mL production medium inoculated with 12%(volume fraction) seed culture and incubated at 28 ℃,180 r/min for 216 hours.The inhibition zone produced by the filtrate of the fermented broth was 3.04 cm in diameter.[Conclusions] A lab-scale fermentation process for strain A03 was successfully established in the study.The fermentation level with the optimized process was 52.0% higher,and the fermentation period was 33.77% shorter than that by the basic fermentation process.The study result provided a set of valuable parameters for the metabolic control and scale up of the fermentation process of strain A03.