Effect Of Alkaline PH Shock On The Fermentation Of Validamycin A And Its Mechanism

Validamycin A(Val-A)is a widely used antifungal antibiotic with strong rice sheath blight resistance.Fermentation pH is a critical factor which affects the fermentation process of Val-A.Environmental stress is an important way to promote the production of secondary metabolites in Streptomyces.However,the research on the fermentation process of Val-A by pH shock is limited.In this paper,the production of Val-A under different pH shock conditions was studied in detail.It was found that the treatment with sodium hydroxide solution at 20 h obtained a higher yield together with faster protein synthesis and sugar consumption.In the present study,the gene expression profile of Streptomyces hygroscopicus 5008 after pH shock was analyzed by gene chip and qRT-PCR.The results showed that genes related to amino acid metabolism,carbon metabolism and electron respiratory chain were significantly up-regulated,and some transcription factors and signal transduction system-related genes expression are also raised.Respiratory activity and glutamate concentration increased.Val-A production has been promoted by a series of complex mechanisms to convey and response to the environment stress signal,which led to enhancement of glutamate metabolism and respiration activity.The paper also described a new method for rapid detection of contaminants in Val-A fermentation.GC-MS combined with PCA was used to analyze the differences of odorants in the fermentation broth,which formed a new method to detect the contamination early in the fermentation process.Kinds of contaminant microbes and types of fermentation medium had no effect on the result.