Breeding Of L-Glutamic Acid Hyper-producer And Optimization Of Its Fermentation

In this paper, the fermentation principles of metabolism control were applied into original strain improvement of Corynebacterium melassecola GL-3 for the overproduction of L-glutamic acid. Then the compositions of medium and the conditions in fermentation were studied. The main research contents and results were as follows:Through examination the accuracy of the biological sensing method , combining the experimental specific circumstances, bio-sensing method for breeding strains detected L-glutamic in experiments was established. The reclaim of average bio-sensing of this method was 99.7%. This method was simple, rapid and economical.The L-glutamic producer was derived from the original strain Corynebacterium melassecola GL-3 by chemical and physical mutation methods, the plate screening with: High osmotic pressure, succinate as sole carbon sourse, NaF, SG, Gln. A strain N77-124(High osmotic pressure tolerance,Sucg,NaFr,SGr,Glnr) which could accumulate 110g/L L-glutamic acid.under un-optimization condition was acquired.The optimization of medium contents and fermentation conditions for N77-124 was conducted. The optimum seed medium conditions were pH 7.2 and the optimum medium volume was 30mL/250mL. The optimum fermentation medium contains glucose 161g/L, corn steep liquor 3.0g/L, K2HPO4·3H2O 2.0g/L, MgSO4·7H2O 0.8g/L,Urea 5.5. The optimum fermentation conditions were 500mL contains 20mL broth, initial pH7.5, inoculated time 8 h, culturing at 30±1℃on reciprocating shaker, shaking speed 100r/min, seed volume 10%, fermentation time 36h. After optimization, the production of L-glutamic was up to 114g/L with high conversion efficiency of 71%.N77-124 strains flask fed-batch fermentation of the preliminary was studied. The optimum initial glucose concentration was 80g/L. The lowest glueose concentration maintained was 10-20g/L. The optimum feeding glucose concentration was 600g/L. The control of fermentation temperature in this way: 0-10 h 34℃, 10-20 h 36℃, 20 h 38℃. The production of L-glutamic acid was up to 117g/L and conversion rate was up to 72% after 32 h.