Breading Of L-Glutamine Producer And Optimization Of Fermentation Process

L-glutamine is found most abundantly in mammals blood, it is widely used in clinical medicine, nutrition and animal feed. It has broad marketing space and developing prospect.In this paper, the original strain Corynebacterium acetoacidophilum LG-3 was mutated gradually by UV and DES treatments, a L-glutamine producing strain LG-65 was obtained based on metabolic control principle.Then, the fermentation conditions in shaker flask and 7 L fermentor were studied, and the batch fermentation kinetic in batch culture with 7 L fermentor was analysised. The study work and results are as follows:(1) The original strain Corynebacterium acetoacidophilum LG-3 was mutated gradually by UV and DES treatments and then the mutated strains were screened by sulfaguanidine(SG) and high concentration (NH₄)₂SO₄, a L-glutamine producing strain LG-65 was obtained. The L-glutamine yield of 43.5 g/L was obtained after culturing in shaker flask with unoptimized condition for 72 hrs, and its yield is 34.3 % more than original strain.(2) The culture conditions of seed and fermentation were studied for LG-65, the optimal medium and culture conditions were obtained after being optimized. After optimization, the productivity was up to 47⁴8 g/L, improved 4.9 g/L.(3) Based on the optimum condition in shaker flask, the batch fermentation in 7-liter fermentor was performed with LG-65. 51.2g/L L-glutamine was obtained after cultured 46 hrs in 7-liter fermentor. The fed-batch fermentation was studied also. The effects of (NH₄)₂SO₄ and original glucose on L-glutamine yield were compared while in fed-batch culture with flask shaker. The yield of 55.0 g/L was obtained in fed-batch culture for 40 hrs with 7-liter fermentor based on the optimized fed-batch fermnetation condition.(4) Based on the experimental result of LG-65 in batch culture with 7-liter fermentor, the kinetic models of batch fermentation were studied. And the models of strain growth, product yield and substrate consumption were obtained. After fitted by software MATLAB, the fitting parameters and fitting curve were obtained which could reflect the batch culture process of LG-65.