Thorough research and modification of one-carbon units cycle for improving L-methionine production in Escherichia coli

Methionine is the only one of the essential amino acids that contain sulfur, widely used as a feed additive in agriculture. In this study, the availability of 5-methyl-tetrahydrofolate was confirmed as the main limitation in the complex multibranched biosynthetic pathway of L-methionine. The cycle of one-carbon units was thoroughly investigated and modified to supply 5-methyl-tetrahydrofolate for L-methionine production, such as enhancing the supply of precursor, expediting the conversion rate of the cycle, introducing exogenous serine hydroxymethyltransferase and increasing pool size of one-carbon units carrier. The final strain MYA/pAmFA-4 was able to produce 20.89 g/L L-methionine by fed-batch fermentation, which was the highest titer reported in the literatures. This study is instructive for other metabolites biosynthesized needing one-carbon units or having a complex multibranched biosynthetic pathway.

Automated summary

In this study, the availability of 5-methyl-tetrahydrofolate was identified as the main limitation in the biosynthesis of L-methionine. The one-carbon unit cycle was thoroughly investigated and modified to enhance the production of L-methionine. The final strain MYA/pAmFA-4 achieved the highest reported titer of 20.89 g/L L-methionine. This study provides insights for the biosynthesis of other metabolites with complex multibranched pathways or requiring one-carbon units.