Effects of pgk and ilvN genes on L-serine production by Corynebacterium glutamicum.

To increase the carbon flux of the L-serine synthesis pathway of Corynebacterium glutamicum A36, the phosphoglycerate kinase (pgk) was overexpressed to increase the accumulation of 3- phosphoglycerate, the precursor of L-serine. It had no significant effect on the L-serine titer. Furthermore, the acetohydroxyacid synthase gene ilvN of the byproduct L-valine synthesis pathway was knocked out. Only a little L-valine was accumulated after knocking out ilvN, however, the recombinant strain was not an auxotrophic strain. The titer of L-serine decreased, and the addition of L-valine was benefit to the production of L-serine. Then, L-valine was added to the medium. When L-valine was 750 mg/L, the titer of L-serine was 34. 19 g /L, with the yield of 0. 34 g / g, and the productivity was 0. 28 g /( L h), increased by 11. 8%, 13. 3% and 12. 0%, respectively, compared to the original strain A36. [ABSTRACT FROM AUTHOR]