In order to improve the yield and quality of L-valine by microorganism in fermentation industry, two strategies including breeding high production activity strains and optimizing the fermentation conditions should be taken into account. The metabolic control fermentation breeding has become an important strain improvement strategy. In this paper, breeding of L-valine producer NJ-5 was conducted. Then, fermentation conditions were optimized and the metabolic flux distribution of the three L-valine producers ...