High-Yield Biosynthesis of 3-Hydroxypropionic Acid from Acetate in Metabolically Engineered <i>Escherichia coli</i>

The third-generation biorefineries aimed at "carbon-negative" production of fuels and chemicals utilizing one-carbon molecules and renewable energy sources were raised to tackle the pressing climate change and food scarcity issues. Acetate derived from syngas fermentation, a viable nonfood carbon source, has recently been elevated in bulk chemicals biosynthesis. In this study, we successfully engineered <i>Escherichia coli</i> to produce 3-hydroxypropionic acid (3-HP) from acetate via the malonyl-CoA pathway. Initially, the constitutive promoter of the 3-HP biosynthetic pathway for efficient 3-HP production was screened in acetate-based medium. Then, efforts were focused on reducing the competition for malonyl-CoA by inhibiting the fatty acids (FAs) synthesis pathway. Furthermore, we enhanced the supply of NADPH and acetyl-CoA through cofactor engineering. The engineered strain ZWR18(M*DA) accumulated 5.53 g/L 3-HP, corresponding to a yield of 0.732 g/g, and achieved 97.60% of the theoretical yield. In whole-cell catalysis, ZWR18(M*DA) produced 23.89 g/L 3-HP with a yield of 0.734 g/g, reaching 97.87% of the theoretical yield. Utilizing syngas-derived acetate for whole-cell catalysis allowed ZWR18(M*DA) to accumulate 18.87 g/L 3-HP with a yield of 0.58 g/g. These results indicate that acetate from syngas can serve as a cost-effective and environmentally friendly alternative to traditional carbon sources, offering a sustainable biorefinery pathway for industrial biomanufacturing.