The invention discloses a method for fermenting and producing L-
leucine, which comprises the following steps: loading LB medium into a
shake flask, inserting slant strains, and then placing the
shake flask on a
shaker for 28 hours of cultivation to obtain seed liquid, Standby; then the seed liquid is connected to a fermenter with a
fermentation medium for
fermentation and cultivation; during the
fermentation process, by controlling the stirring speed and
air volume, the dissolved
oxygen in the first 20 hours of the fermentation process is 6-8 mg / L, and the dissolved
oxygen after 20 hours is 6-8 mg / L. 3-6mg / L; the pH of the fermentation process is controlled by automatic feeding of
ammonia water, and the pH is controlled to be 6.4-6.7 before the OD value of the
bacteria reaches 25. After the OD value of the
bacteria increases to 25, the pH increases by 0.1 per hour until it increases Remains unchanged after 7.2; L-
leucine is extracted and refined after fermentation. The method of the invention shortens the fermentation period, improves the fermentation output, has simple and easy control technology, and is low in cost, and is very suitable for large-scale industrial application.