Engineering Microbial R- and S- β-Hydroxybutyrate Production

Beta-hydroxybutyrate (BHOB) is a therapeutically valuable enantiomeric ketone body that is synthesized by both prokaryotes and eukaryotes. Bacterial synthesis of BHOB has so far mostly been exploited for the synthesis of biofuels and to a lesser extent for the pharmaceutical industry. In this study, we carefully evaluated the expression, induction, selection, and detection elements and identified multigene pathways to direct the synthesis of physiologically relevant amounts of BHOB. Utilizing the reversal of the beta−oxidation pathway that has previously been used for biofuel generation, we engineered E. coli strains with a prebiotic-activated circuit to secrete either (S)−BHOB or (R)−BHOB. Our findings demonstrate high-yield microbial BHOB production with a defined enantiomeric composition and highlight its therapeutic potential for cancer and gut−brain axis involving disorders.