Studies On L-Arginine Fermentation Conditions

In this paper, the optimal seed medium, the best fermentation medium in flask-shaking and the batch fermentation process in 5-liter fermentor and the analysis of dynamic were investigated for L-arginine production with recombinant Escherichia coli LGE35(Thr^-, Met^-, Kan⁺). The results are as follows:[1] The genetic markers were tested for E.coli LGE35(Thr^-, Met^-, Kan⁺). The results showed that the genetic markers were not lost. The optimal seed medium was optimized by one-variable-at-a-time and orthogonal experiment methods. The optimum seed medium composition was found to be: sucrose 20g/L, beef extract 50g/L, peptone 20g/L, L-methionine 0.05g/L, L-threonine 0.05g/L,kanamycin 0.1g/L, calcium carbonate 20g/L.[2] Based on the one-variable-at-a-time experiment of fermentation medium, three main significant factors of the sucrose, ammonium sulfate and yeast extract powder which affect the flask-shaking batch fermentation production of L-arginine secreted by recombinant E.coli LGE35 were screened by the Plackett-Burman design. The optimal level of these three significant factors and their interactions were studied by response surface methodology. The polynomial regression model was established and the optimum medium composition was determined as follows: sucrose 71g/L,ammonium sulfate 31g/L,yeast extract powder 14g/L, MgSO₄·7H₂O 1g/L, K₂HPO₄ 3g/L, L-methionine 0.15g/L, L-threonine 0.1g/L, kanamycin 0.05g/L, FeSO₄ 0.01g/L,MnSO₄ 0.01g/L,VB1 0.01g/L. The optimum fermentation condition was studied. The results showed that: temperature 30℃, pH7.0, inoculum 8%, flask-shaking speed 240 r/min.. Under optimum conditions, after the strain E.coli LGE35 was cultured 96 hours, it can be produced 16.04g/L of L-arginine which increased about 32.78% more than before.[3] Based on the flask-shaking batch fermentation condition, the batch fermentation was investigated with strain E. coli LGE35 in 5-liter fermentor. The L-arginine batch fermentation kinetics was studied based on the experimental data from the batch fermentation of 5-liter fermentor. Three kinetic models were constructed which could reflect the regularity of growth, product formation and substrate consumption in the process of batch fermentation.