(191bd) Use of an Escherichia coli pyruvate-Overproducing Platform Strain to Produce ?-Valine

Biocatalytically derived, carbon-neutral chemicals are becoming increasingly attractive over traditional catalytic methods, but are impeded by the slow, metabolic engineering design-build-test cycle. To expedite this process, a precursor-abundant strain to industrially relevant chemicals will enable high-throughput engineering of diverse biosynthesis pathways. To this end, the metabolic potential of Escherichia coli was assessed computationally and pyruvate identified as the optimal precursor to produce commercially relevant chemicals. Subsequently, a genome-scale metabolic model of E. coli was used to design strains that achieved astonishing pyruvate yields up to 95% of the theoretical maximum. Next, as a proof-of-concept, ÊŸ-valine was chosen as a target for overproduction to test the platform capabilities of a pyruvate-producing strain since it is an amino acid widely used as a nutritional supplement in several industries with a global demand of about 500 tons annually. Currently, a pyruvate-producing E. coli strain harboring a plasmid expressing ÊŸ-valine biosynthetic genes has been engineered to achieve 69% of the theoretical maximum yield, the highest reported for E. coli, as opposed to 39% for wild-type E. coli with the same plasmid, in approximately 22 hours of aerobic culturing in a defined, glucose minimal medium. This study demonstrates that a pyruvate platform strain is, indeed, a versatile tool to rapidly engineer strains to produce various chemicals.