AUTHOR=Lo Jonathan , Humphreys Jonathan R. , Magnusson Lauren , Wachter Benton , Urban Chris , Hebdon Skyler D. , Xiong Wei , Chou Katherine J. , Ching Maness Pin 

TITLE=Acetogenic production of 3-Hydroxybutyrate using a native 3-Hydroxybutyryl-CoA Dehydrogenase

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.948369

DOI=10.3389/fmicb.2022.948369

ISSN=1664-302X

ABSTRACT=<p>3-Hydroxybutyrate (3HB) is a product of interest as it is a precursor to the commercially produced bioplastic polyhydroxybutyrate. It can also serve as a platform for fine chemicals, medicines, and biofuels, making it a value-added product and feedstock. Acetogens non-photosynthetically fix CO<sub>2</sub> into acetyl-CoA and have been previously engineered to convert acetyl-CoA into 3HB. However, as acetogen metabolism is poorly understood, those engineering efforts have had varying levels of success. 3HB, using acetyl-CoA as a precursor, can be synthesized by a variety of different pathways. Here we systematically compare various pathways to produce 3HB in acetogens and discover a native (<italic>S</italic>)-3-hydroxybutyryl-CoA dehydrogenase, <italic>hbd2</italic>, responsible for endogenous 3HB production. In conjunction with the heterologous thiolase <italic>atoB</italic> and CoA transferase <italic>ctfAB</italic>, <italic>hbd2</italic> overexpression improves yields of 3HB on both sugar and syngas (CO/H<sub>2</sub>/CO<sub>2</sub>), outperforming the other tested pathways. These results uncovered a previously unknown 3HB production pathway, inform data from prior metabolic engineering efforts, and have implications for future physiological and biotechnological anaerobic research.</p>