Effects Of Gene SerA And SdaA On Accumulation Of L-serine In Corynebacterium Glutamicum SYPS-062

This paper was focused on Corynebacterium glutamicum SYPS-062, a strain isolated from soil sample that can directly product L-serine from sugar as substance. Based on molecular biology techniques, using recombinant DNA technology and other means of molecular, we analyzed, modified the key enzyme genes of L-serine metabolic pathways in the strain and constructed a genetic engineering strain. The fermentation performance of the recombinant strain in shake flask was studied3-Phosphoglycerate dehydrogenase (3-PGDH), coded by the gene serA, is the initial enzyme of the L-serine biosynthetic pathway with activity being inhibited by high concentrations of L-serine in C. glutamicum. Mutein of gene serA that 591 nucleic acid bases was truncated at the 3'-terminal end was constructed. When expressed in E. coli, mutein serA^Δ591 showed a specific PGDH dehydrogenase activity of 1.092 U/mg protein. The activity reduced to 74.13% compared with the protein coded by gene serA but no longer being sensitive to the high concertration of L-serine.According to the result before, gene serA^Δ591 and serA were overexpressed respectively in C. glutamicum SYPS-062. It showed that the activity of 3-PGDH in C. glutamicum (pJC1-tac-serA^Δ591) and C. glutamicum (pJC1-tac-serA) increased by 47.42% and 67.38%. However, L-serine in C. glutamicum (pJC1-tac-serA^Δ591) was increased by 8.63% and increased by 1.84% in C. glutamicum (pJC1-tac-serA). It showed that the overexpressed of genes serA^Δ591 was more conducive to the improvement of L-serine production. L-serine dehydratase (Ser-DH) catalyze the degradation of L-serine to pyruvateis ,it was encoded by the gene sdaA, on this paper we obtained the homologous fragment of gene sdaA homologous fragment by crossover-PCR, and the gene sdaA C. glutamicum SYPS-062 was deletion based on the principle of homologous recombination. When the gene sdaA coding SerDH was deletion, the unit cell L-serine production increased 15.13%, and there was no significant difference in the consumption of sugar.According to the results above and the key position of L-serine in central metabolism, a strain as did the overexpression of gene serA^Δ591 and the deletion of gene sdaA was constructed. As the change in the metabolism of L-serine in the recombinant C. glutamicum SYPS-062ΔsdaA(pJC1-tac-serA^Δ591), the recombine strain was resulted in a transient accumulation of L-serine increased 23.18% with a 53.94% improved in the unit cell by fermentation with the slower growth.Due to the regulation of microbial metabolism network by itself, Analyzing the mechanism of L-serine producing from the cell metabolism, modifing the key genes of L-serine metabolic pathways, constructing a genetic engineering strain of high yields of L-serine is the future development trends.