S88: A platform pathway for the production of value-added chiral hydroxyacids

Hydroxyacids are versatile, chiral compounds that can be readily modified into several useful derivatives.  We have developed a novel microbial system for the biosynthesis of several 3-hydroxyalkanoic acids and lactones through the condensation of various acyl-CoA moieties as well as the various tools we use to manipulate acyl-CoA biochemistry.  One such molecule, 3-hydroxy-γ-butyrolactone (3-HBL), has been defined as a “top value-added chemical from biomass” by the US Department of Energy.  The compound is frequently used in the pharmaceutical industry as the central building block for many blockbuster drugs like Zetia^(R) and in several statins (cholesterol-reducing drugs) such as atorvastatin and rosuvastatin.  There are no reported enzymes or metabolic pathways, natural or engineered, for the biosynthesis of 3-HBL.  Our group established the first complete biosynthetic pathway towards 3-hydroxy-γ-butyrolactone (3-HBL) and its hydrolyzed form, 3,4-dihydroxybutyric acid (DHBA) in Escherichia coli, and demonstrated the synthesis of 3-HBL and DHBA at the shake flask scale, using glucose and glycolate as feedstocks. We have since constructed a pathway for the endogenous production of glycolate to achieve direct synthesis of 3-HBL and DHBA from glucose as a single feedstock.  Work on development of the integrated pathway, the accompanying host engineering, and ongoing efforts to improve pathway productivity will be presented.  Direct synthesis of DHBA and 3-HBL from glucose opens avenues to their syntheses from other simple sugars derived from biomass. Results will also be presented on the flexibility of the platform pathway for the production of other, structurally distinct 3-hydroxyalkanoic acids.