Effect Of Trimethylglycine On The Fermentation Of L-Leucine

L-leucine is one of the eight essential amino acids. It is widely used in medicine, food and so on. The production of L-leucine could get enormous economic value and the development of amino acid industry would bring giant market. Under the guidance of the metabolic control fermentation theory, the strain Corynebacterium glutamicum JL1211( Met-+2-TAr+α-ABr+β-HLr+SGr+Rifr) was tested by shaking flask fermentation and 5L fermentor fermentation. The optimized results like the components of the fermentation culture and the optimal feeding strategy are obtained. The metabolic fluxs were analysed and the transcriptome analysis was taken. The results are as followed:(1) The effects of trimethylglycine, VB5 and VB12 in the fermentation culture were tested. The results showed that trimethylglycine added in the fermentation culture could enhance the production of L-leucine and shorten the fermentation period. Under the optimal proportion of fermentation culture, with trimethylglycine1.8g/L、VB50.1mg/L and VB120.2mg/L, the fermentation period was shrinked to 33h; with trimethylglycine 3g/L、VB50.3mg/L、VB120.2mg/L, the production of L-leucine was increased to 8.9g/L.(2) Through the 5L fermentor fermentation, the optimal feeding strategy and fermentation culture composition were obtained. With trimethylglycine added in the glucose by 1.5‰ mass concentration feeding into the fermentor during fermentation, the concentration of glucose being controlled in 10g/L, the production of L-leucine was enhanced to 45.8g/L. Different kinds of trimethylglycine, like sigma trimethylglycine, anhydrous trimethylglycine, phosphate trimethylglycine and hydrochloride trimethylglycine, were tested to ensure the most influencial kind of trimethylglycine. The maximum L-leucine production was obtained by adding sigma trimethylglycine.(3) Comparing the data of trimethylglycine adding in the glucose by 1.5‰ mass concentration feeding into the fermentor during fermentation, the concentration of glucose controlled in 10g/L, with the data of the concentration of glucose controlled in 10g/L during fermentation, the metabolic fluxes were analysed. Pyr node and α-KG node were identified to be the most important nodes for enfluencing the production of L-leucine. The adding of sigma trimethylglycine could increase the conversion rate of Pyr and α-KG.(4) By comparing the fermentation liquid sample after transcriptome analysis, the ABC transporters were significantly affected. The genes expression levels were raised. The cellular membrane permeability was increased and that caused the high L-leucine production.