The Effect Of Folate Pathway Regulation To The L-serine Accumulation By Corynebacterium Glutamicum SYPS-062

The tetrahydrofolate (THF) was generated in folate pathway in C. glutamicum, and engaged in regulating SHMT enzyme. SHMT enzyme catalysed the conversion of L-serine into glycine. The study focused on a L-serine producing strain C. glutamicum SYPS-062, which can accumulate L-serine directly from sugar substances. The gene pabAB overexpression strain C. glutamicum SYPS-062(ppabAB) and the gene pabAB deletion strain C. lutamicum SYPS-062△pabAB were constructed, the effect of pabAB to the L-serine accumulation in C. glutamicum SYPS-062, and the effect of other substances in the folate pathway to the L-serine acumulation were also studied. The results were as following:(1) The homologous fragment△pabAB was amplified through crossover PCR, and was ligased to pK18mobsacB,then the C. glutamicum SYPS-062△pabAB was constructed through homologous recombination.(2) The results showed that the ADC synthase raised 33% with the gene pabAB overexpression compared with the original strain, while it decreased 61% after the gene pabAB was deleted. Meanwhile the SHMT activity of C. glutamicum SYPS-062 (ppabAB) increased 30%, theμm raised 48%, and the Yp/x decreased 36.2% compared with that of the original srtain C. glutamicum SYPS-062; The SHMT activity of C. glutamicum SYPS-062△pabAB decresaed 20% when compared to that of the original strain, theμm decreased 32%, while the Yp/x increased 12% compared with the original strain.(3) The accumulation of L-serine by C. glutamicum SYPS-062△pabAB could reach up to 7.8 g/L in the optimized medium, which increased 14% compared to that of the original strain.