Efficient biosynthesis of 3-hydroxypropionic acid in recombinant Escherichia coli by metabolic engineering

3-Hydroxypropionic acid (3-HP) is a platform compound that can produce many chemical commodities. This study focuses on establishing and optimizing the production of 3-HP in E. coli. We constructed a series of engineered E. coli strains which can produce 3-HP via the malonyl-CoA pathway. To increase the metabolic flux of acetyl-CoA, a precursor for the synthesis of 3-HP, CRISPR/Cas9-based DNA editing technique was used to knock out the genes encoding pyruvate oxidase (poxB), lactate dehydrogenase (ldhA) and phosphate transacetylase (pta), thereby reducing the formation of by-products. Concurrently, the acetyl coenzyme a carboxylase gene (accDABC) is overexpressed on the chromosome with the objective of augmenting intracellular acetyl-CoA levels and, consequently, 3-HP production. Next, we introduced a plasmid containing a codon-optimized malonyl-CoA reductase gene (mcr) into the engineered strain. Finally, we constructed a transcription factor-based metabolite biosensor utilizing the PpHpdR/PhpdH system, followed by the screening of mutant strains for enhanced 3-HP production through adaptive laboratory evolution. Combining the above metabolic engineering efforts with optimisation of media and fermentation conditions, the 3-HP titer of the engineered strain WY7 increased from an initial titer 0.34 g/L to 48.8 g/L. This study encourages further research in metabolic pathway optimizationto produce 3-HP.