Screening Of High Yield Of Nosiheptide Strain And Studies On Its Fermentation

Nosiheptide is sulfur polypeptide antibiotic by S.actuosus production, mainly inhibits the growth of gram positive bacteria, that can promote the absorption of nutrients, improve the utilization rate of feed.Screening high production strain of Nosiheptide by fusion of inactivated parental protoplasts prepared by using lysozyme.The strain of GM-6 was isolated and the increased yield was about 5.3% higher than that of the parent strain. The titer of Y3-52 has reached 1009mg/L and its increased yield was about 15%.Setting different concentrations of base analogs 5-BU and applied to the plate and then we obtains the sudden change strain of B40,enhances 5.8% compared to the primitive strain.In order to avoid the resistant of the strains,the composite mutation of the strains by ARTP and 5-BU,we get the strain of AH-12 has been 15.3% increased.The chemical mutagen EMS (ethylmethane sulfonate) was employed to create a mutant collection by treating the strain and we get the strain of E-12 has been 50%increased to the starting strain of Y19.The fermentation condition was determined by using the single-factor experiments and the response surface method.The optimized fermentation condition of Streptomyces actuosus was obtained as follows:soybean of 37.97g/L,liquefied starch of 74.13g/L,yeast extract of 2.63g/L, CaCO3 of 4g/L, initial pH of 6.5, Tween80 of 1.5mL/L, Mn2+0.02%.The production of nosiheptide reaching 1394mg/L, which was increased by 8% compared with the original condition.The strain was verified by pilot in 3L fermentation tank. Based on the dynamic analysis of biomass, nosiheptide titer, sugar, amino nitrogen and pH value during the synthesis of nosiheptide by S.actuosus. The fermentation process was constantly regulated by different single pH value to investigate the dynamic variation principles of biomass and specific growth rate of S.actuosus and the nosiheptide synthesis. S. actuosus has maximum specific growth rate with pH6.5-7.0 while nosiheptide synthesis titer was highest with pH7.0. The optimal dissolved oxygen is 40%.Optimization for the fed-batch fermentation process of Nosiheptide is in the 72h with 400mL 7% liquefied starch and 200mL 4% soybean.In the condition,nosiheptide titer was 1677μg/mL on 3L fermentation tank which increased by 45% than before optimization.