Screening Of High-yield Natamycin Strains By Mutation And Optimization Of Fermentation Process

Natamycin is one of kind of macrolide antibiotics with26-membered ringpolyene structure, which is predominantly a strong, broad-spectrum antifungal agent.It is widely used in food industries and medicial treatment. However, the yield ofnatamycin at present is very low, so the application of natamycin is limited severelydue to the high cost of production. Therefore, it is very improtant to enhance theresearch and development of natamycin production process. In this study, the highproduction strain was selected by mutation. Meanwhile, fermengtation conditions wereoptimized. The major research contents and results are as follows:Streptomyces natalensis N8was used as the strating strain. The fermentationcharacteristics were studied and results showed that the yield of natamycin wasreached to1300mg/L when the seed culture time was38h, inoculum size was10%, pHwas7.2, culture temperature was28℃and fermentation medium composition wasas（%）: Glucose2, soluble starch4，soybean powder4，Yeast Extract0.7.Composite mutagenesis of ultraviolet and low energy nitrogen ion beam werestudied. Results showed that the optimal mutagenesis parameters: UV lamp power15W, the sample distance from the tube30cm, treatment time30s and the optimal lowenergy nitrogen ion beam mutagenesis parameters: nitrogen ion beam energy is8kev,dose2×10¹⁴ions/cm². Minimum inhibition concentration of streptomycin sulphate was0.6μg/mL. In these conditions,UV-N-8and UV-N23were obstained by repeatedmutation and screening when MIC of Streptomycin sulfate0.6μg/ml. And natamycinproduction reached to2130mg/L,2000mg/L, increased by71%,65%respectively.Streptomyces natalensis mutation strain UV-N-8was used as the original strain.Four factors with significant influence were chosen and optimized by response surfacemethods. Fermentation process parameters were obtained: glucose1.783%, solublestarch4.498%, yellow DouBing powder3.618%, yeast extract of0.694%. Prediction value of natamycin can be up to2212mg/L at this condition and the actual averagevalue2198mg/L,increasing by3.2%.According to the natamycin synthesis pathways, precursors such as sodiumacetate, sodium propionate, sodium butyrate and different fungal elicitors were studied.The results showed that the natamycin was highest when sodium propionate wasadded to a final concentration of0.6%at24h during the fermentation. In addition,fungal elicitors made from Penicillium chrysogenum and Cunninghamella echinulataboth can promote the natamycin yield.