Optimization Of The Strain Producing L-isoleucine And Its Fermentation

The thesis use gradient spread plate method to separate a high yield L-isoleucine single colony as my experiment strain.Use the method of paper chromatography to determine L-isoleucine content.Optimize the seed culture condition and fermentation process,in order to enhance the yield of L-isoleucine content,establish the foundation of commercial process.Optimizing the method of paper chromatography,ensure the condition of paper chromatogram,the additive amount of ninhydrin is 0.7%,proportion of developing solvent is n-butyl alcohol:glacial acetic acid:water=12:3:5,develop 5 hours,elution time is 40min,absorb wavelength is 516nm.Use gradient spread plate method to obtain single colony,obtain a high yield L-isoleucine strain form thirty single colonies,L-isoleucine content reach 9.40g/L at the condition of low rotate speed.Ensure the additive amount of corn steep liquor is 4%in seed medium,culture time is 28h.Optimize the fermentation process,ensure carbon source of fermentation medium is glucose,additive amount is 14.5%,nitrogen source is dry corn steep liquor,additive amount is 0.3%,fermentation temperature is 30℃,pH 6.8～7.1,rotate speed of table concentrator is 200r/min,inoculum size is 10%.Use the optimized fermentation process condition to experiment,average L-isoleucine content reach 23.63g/L.Through experiment to know about the influence of sodium citrate and glycine betaine for L-isoleucine fermentation,the additive amount of sodium citrate is 2%,acid production reach 25.59g/L,enhance 14.2%compare with none sodium citrate.The additive amount of glycine betaine is 1%,acid production reach 24.79g/L,enhance 11.2%compare with none glycine betaine.