Thursday, July 30, 2009 - 10:00 AM
S140
Engineering E. coli for commercial production of optically pure D(-) and L(+)-lactic acid
Tammy B. Grabar, Myriant Technologies, LLC, 66 Cummings Park, Woburn, MA 01801, Shengde Zhou, Biological Sciences, Northern Illinois University, 155 Castle Dr., DeKalb, IL 60115, and Lonnie O. Ingram, Microbiology and Cell Science, University of Florida, Bldg 981, Museum Road, Gainesville, FL 32611.
Full commercialization of bio-based lactic acid is critically dependent on the inexpensive and efficient production of optically pure D(-) or L(+) enantiomers. An Escherichia coli derivative was engineered to produce high concentrations of lactic acid in mineral salts medium in a simple batch fermentation. Under fermentative conditions, generation of ATP for growth was tightly coupled to lactate dehydrogenase by deletion of genes involved in other NADH oxidation routes. Therefore selection of strains with improved growth characteristics also selected for increased lactic acid production. An additional deletion, mgsA, was introduced to improve optical purity. A D(-)-lactic acid production strain, TG113 (ΔadhE, ΔackA, ΔpflB, ΔmgsA, Δfrd), contains only native DNA and was engineered and evolved to produce high titers of chirally pure (>99.9%) D(-)-lactic acid. Strain TG108 (ΔldhA::ldhL, ΔadhE, ΔackA, ΔpflB, ΔmgsA, Δfrd) contains the ldhL gene from Pediococcus acidilactici and was engineered to produce only L(+)-lactic acid. In mineral salts medium containing 1 mM betaine, both strains produced over 115 g (1.3 mol) lactate from 12% (w/v) glucose, >95% theoretical yield. Further improvements for commercial production were selected for by metabolic evolution.
See more of Metabolic engineering strategies for strain improvement
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See more of The Annual Meeting and Exhibition 2009 (July 26 - 30, 2009)
See more of Invited Oral Papers
See more of The Annual Meeting and Exhibition 2009 (July 26 - 30, 2009)