3-Hydroxypropionate production using a novel malonyl-CoA-mediated biosynthetic pathway in genetically engineered E. coli Strain
3-hydroxypropionic acid (3-HP) is a promising platform chemical with a wide range of applications. Traditional chemical synthesis of 3-HP is well-established, but resource limitations, high price and the toxicity of the used raw materials do not meet the new sustainable development goals. Microbial synthesis of 3-HP by fermentation should become a promising and attractive route mainly for environmental production, renewable resources, sustainable development. In this paper, to biosynthesize 3-HP directly from malonate, a novel malonyl-CoA-mediated biosynthetic pathway is successfully assembled as follows: firstly, various transporters involved in malonate transportation was systematically investigated and screened; secondly, to biosynthesize the 3-HP, an original strategy is employed by heterologously co-expressing the mutant of malonyl-CoA reductase (MCR) from Chloroflexus aurantiacus and malonyl-CoA synthetase (MatB) from Rhodopseudomonas palustris in the Escherichia coli C43 (DE3) strain, which was screened from three different MatB enzymes; finally, to further enhance the production of 3-HP, native transhydrogenase (PntAB) and NAD kinase (YfjB) genes were expressed so as to increase the NADPH supply in E. coli. The final genetically modified strain, SGN78, showed a significant improvement in the malonate utilization and produced 1.20 ± 0.08 g/L of 3-HP in flask culture. Our work thus led to a demonstration of 3-HP production in E. coli with the shortest route for 3-HP biosynthesis, which was composed of only three steps from substrate. And it also opens the gateway for biosynthesis of 3-HP or other malonyl-CoA-based valuable chemicals directly from malonate in E. coli.