High-level production of vitamin K2 in Escherichia coli via modular molecular engineering

Menaquinone-7 (MK-7), a key form of vitamin K2 with wide-ranging nutritional and pharmaceutical applications, has attracted increasing interest for microbial production. Here, we developed an integrated modular metabolic engineering strategy in Escherichia coli to enhance MK-7 biosynthesis. Cellular membrane capacity and acetate metabolism were rewired to improve precursor supply for the mevalonate (MVA) pathway, while arabinose induction was applied to overexpress three critical enzymes, including BsHepPPS (Bacillus subtilis), EcMenA (E. coli), and BsUbiE (B. subtilis). Among them, EcMenA was identified as a major bottleneck. Rational protein engineering based on folding free energy analysis and consensus design yielded the EcMenA mutant G110W, which produced 102.55 mg/L MK-7 in shake-flask fermentation, a 57.2 % increase compared with the wild-type (WT) enzyme. Further active-site hotspot random mutagenesis generated a G110W-Q57T double mutant, raising MK-7 production to 176.38 mg/L, a 72 % increase compared to the single mutant. Optimization of EcMenA expression cassette by ribosome binding site redesign using a generative network further improved MK-7 titer to 227.53 mg/L in shake flasks. Finally, scale-up fermentation in a 50-L bioreactor, combined with optimized fermentation strategies, achieved a maximum MK-7 titer of 2.18 g/L. This study establishes a systematic framework integrating metabolic rewiring, enzyme engineering, and expression optimization, providing a robust platform for industrial-scale MK-7 production in microbial hosts.