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The effect of betaine on lysine production and the corresponding metabolic flux analysis
Pages: 125-131
Year: Issue:  3
Journal: Bulletin of Fermentation Science and Technology

Keyword:  lysineosmotic pressurebetainemetabolic flux analysis;
Abstract: The osmotic pressure is very high at the end of the lysine fermentation process.Betaine is usually used as osmolyte to relieve the impact of the high osmotic pressure. However, the addition of betaine can inhibit the inner tolerance of E. coli to high osmotic pressure. In order to improve the titer of lysine fermentation, its inner tolerance against osmotic pressure should be activated. When betaine was added at OD562 of 19.5, the productivity increased from 5.6 g/(L·h) to 6.3 g/(L·h), and yield increased from 65% to 68.5%. The increase of initial glucose concentration can also promote the productivity to 6.6 g/(L·h). The combination of inner tolerance and addition of osmolyte can further relieve higher osmotic pressure at the end of the fermentation process than the addition of osmolyte alone. The metabolic flux of high lysine yield process was analyzed. The flux of the reverse conversion of fructose-6 P was 43% higher than the control and TCA cycle flux was 18.6% lower than the control. These results indicated that the removal of betaine from the initial medium and the increase of initial glucose concentration are beneficial to lysine fermentation.
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