(571c) Platform Pathway for the Synthesis of 3-Hydroxyacids As Value Added Products Derived From Biomass

Dhamankar, H. H., Massachusetts Institute of Technology

The dwindling nature of petroleum and other fossil reserves has provided an impetus to microbial synthesis of fuels and value added chemicals from biomass as a renewable resource. The use of biomass as a feedstock requires the design and engineering of novel pathways connecting biomass derived simple sugars to such value added chemicals and fuels. 3-Hydroxyacids (3-HAs) are a versatile class of molecules that can serve as value added products derived from biomass. 3HAs such as 3-hydroxybutyrate and 3-hydroxyvalerate serve as monomers for biodegradable polyhydroxyalkanoates (PHAs) and chiral building blocks for pharmaceuticals and chemicals. We have established a novel platform pathway in E. coli that allows stereospecific synthesis of straight and branched chain 3HAs using glucose and small acid molecules as starting materials. Using this pathway we have been successful in establishing the first biosynthetic route towards the valuable pharmaceutical building block 3-hydroxy-γ-butyrolactone (3-HBL) and demonstrated synthesis of two novel PHA monomers: 3-hydroxyhexanoic acid and 4-methyl-3-hydroxyvaleric acid. Exploiting the full potential of this pathway requires exploring alternative pathway enzymes and engineering them to enhance pathway productivity and improve versatility for the synthesis of other valuable 3HAs. In particular, we are interested in enhancing pathway productivity for synthesis of 3-HBL which features as one of the top ten value added chemicals from biomass in a 2004 Department of Energy report and serves as a versatile chiral building block for the synthesis of drugs like Zetia®, cholesterol reducing synthetic statins such as atorvastatin (Lipitor ®) and rosuvastatin (Crestor ®), antibiotics such as Zyvox® and the nutritional supplement L-Carnitine. Ongoing efforts to identify alternative pathway enzymes for extending the 3HA pathway towards additional value added products as also enhancing enzyme activity and specificity through protein engineering towards specific products will be discussed.