The Preliminary Research On Metabolic Mechanism Of Strain SYPS-062 Directly Produced L-serine From Sugar Substances

SYPS-062 was an L-serine producing strain, which can directly produce L-serine from sugar substances. According to morphology, physiology and biochemical identification(16S rDNA), the bacterial SYPS-062 was identified as Corynebacterium glutamicum. L-serine metabolic network of Corynebacterium glutamicum was constructed to analyze SYPS-062 metabolic flux distribution, and metabolic flux analysis was used to analyze the key enzyme genes in-depth. The results are as follows:1,According to morphology, physiology and biochemical identification(16S rDNA), the bacterial SYPS-062 was identified as Corynebacterium glutamicum. In order to analyze the mechanism of L-serine accumulation in SYPS-062, the growth curve of SYPS-062 in nutrient broth medium was determined.2,The metabolic network of Corynebacterium glutamicum was constructed in this study. Using this model, the metabolic flux distributions of SYPS-062 and ATCC13032 were calculated, which were during the rapid synthesis stage of L-serine in SYPS-062 and the same age in ATCC13032. The results indicated that only 6.4% metabolic flux entered the HMP pathway of SYPS-062 while 29.6 % for ATCC13032 .This provided a sufficient evidence to account for the differences between the two strains.The phosphate phosphoenolpyruvate (PEP) nodes involved the anaplerosis reaction, which indicated that PEP is a key node of Corynebacterium glutamicum. In addition, G-3-P is one of the most important nodes into L-serine metabolic pathway. The MFA results provided a theotical basis for further study.3,Based on the metabolic flux analysis of the two Corynebacterium glutamicum, the differences in metabolic flux distribution could be one of main factors of L-serine accumulation, while serine hydroxymethyl-transferase, which is related with the degradation of L-serine and provide the one-carbon unit for the cell growth, is a key enzyme in Corynebacterium glutamicum. Accordingly, serine hydroxymethyl-transferase gene glyA was studied in this paper. Compared with C. glutamicum SYPS-062, the glyA genes from ATCC13032 shared 99.54% homology in nucleotide sequence. The specific activity of the two recombinant SHMT in E. coli had little difference, indicated that glyA genes was not an important factor of L-serine accumulation in SYPS-062.