Deletion of gene gnd encoding 6-phosphogluconate dehydrogenase promotes l-serine biosynthesis in a genetically engineered strain of Methylobacterium sp. MB200
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To identify potential target genes involved in l-serine biosynthesis in Methylobacterium sp. MB200 and to evaluate the gnd genetically-engineered strains for l-serine production.
Five genes that are not associated with the central metabolic pathway but with l-serine biosynthesis were identified from Methylobacterium sp. MB200 mutants. Gene gnd, encoding 6-phosphogluconate dehydrogenase (PGDH), was selected for further evaluation. The gnd deletion mutant showed a 600% increase in d-serine tolerance and an 80% decrease in PGDH activity compared to Methylobacterium sp. MB200. gnd over-expression did not affect d-serine tolerance, whereas it did increase enzyme-activity up to 136%. Additionally, analysis revealed that in Methylobacterium sp. MB200, l-serine inhibited PGDH activity. The deletion of gnd did not affect growth, whereas it did enhance the biosynthesis of l-serine, resulting in a 225% increase in production of l-serine compared to the wild-type.
gnd, one of the five genes identified here that is associated with l-serine synthesis, can be developed as a potential candidate for metabolic engineering to promote l-serine synthesis in Methylobacterium sp. MB200.
KeywordsMethylobacterium l-Serine Metabolic engineering Gene deletion 6-Phosphogluconate dehydrogenase
This project was supported by the National Nature Science Foundation of China (Grant No. 31160022).
Supplementary Fig. 1—Schematic diagram of construction of the gnd-deleted vector pk18mobSacB-gndLR.
Supplementary Fig. 2—TLC analysis of l-serine synthesis by Methylobacterium sp. MB200 and mutant strains.
Supplementary Fig. 3—PCR verification of the MB200Δgnd, MB200∆gnd(pCM80-gnd), and MB200(pCM80-gnd).
Supplementary Table 1—Bacterial strains, plasmids, and primers used in this study.
Compliance with ethical standards
Conflict of interest
The authors declare no conflict of interest.
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