Combinatorial Metabolic Engineering of Escherichia coli MG1655 Enables Efficient Biosynthesis of Vitamin B6.

Pyridoxine (PN) is the most important commercial form of vitamin B6. Currently, PN is chemically synthesized using toxic chemicals, causing environmental pollution. Microbial production of vitamin B6 offers a more sustainable alternative, but its low productivity makes it difficult to meet commercialization demands. Here, metabolic engineering strategies were used to efficiently improve the PN production. Directed evolution of 4-phosphoerythronate dehydrogenase led to a 4-fold increase in PN production. In addition, the pdxK and pdxH genes were then knocked out to redirect the metabolic flux from pyridoxine 5'-phosphate to PN, and genes involved in glycerol-to-pentose phosphate metabolism were overexpressed to increase precursors for PN synthesis. Finally, the recombinant strain produced 2120.1 ± 7.8 mg/L PN with a productivity of 32.1 mg/L/h by batch fermentation. The strategies reported here will be useful for the efficient and sustainable biobased production of PN.