Elevated production of 3-hydroxypropionic acid in recombinant Escherichia coli by metabolic engineering

Abstract Background: 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 techniques the metabolic flux of precursor acetyl-CoA, CRISPR/Cas9-based DNA editing techniques were used to knock out the genes encoding pyruvate oxidase (poxB), lactate dehydrogenase (ldhA) and phosphate transacetylase (pta) reducing the by-products consumption. Simultaneously, to elevate the production of 3-HP and reduce the burden of the recombinant plasmid in Escherichia coli, the critical precursor of the malonyl-CoA pathway, acetyl-CoA carboxylase gene (accDABC), was overexpressed on the genome. Results: We overexpressed the codon-optimized malonyl-CoA reductase gene (mcr) and increased 3-HP production also via adaptive laboratory evolution using the PpHpdR/PhpdH system to construct metabolite biosensors based on transcription factors. Combining the above metabolic engineering efforts with media and fermentation conditions optimization in a fermentor agitation resulted in the 3-HP titer of the engineered strain increasing about 63.5 times from the initial 0.34 g/L to 21.6 g/L. Conclusions: This study encourages further bioprocess development to produce 3-HP from the malonyl-CoA pathway.