Monday, July 30, 2007 - 8:30 AM
S19
Metabolic Engineering of Saccharomyces cerevisiae for the Fermentative Production of High-Value Terpenoid Compounds
Grace E. Park, Bryan T. Greenhagen, Kevin Nowaczyk, Richard P. Burlingame, and Bryan Julien. Allylix, Inc., A165 ASTeCC Building, University of Kentucky, Lexington, KY 40506
Numerous compounds used as fragrances and flavorings belong to the terpenoid class of plant molecules. The availability of these compounds can vary due to environmental conditions, and their synthesis is expensive due to their complexity. To provide a cost-effective and sustainable source of these compounds, engineered Saccharomyces cerevisiae strains have been developed for their production. Nootkatone, the molecule that gives grapefruit its distinctive smell and taste, is a member of this family. It is used currently as a flavoring for beverages, but its current high cost of production prevents its broader use. Valencene, the biosynthetic precursor to nootkatone, is synthesized from farnesyl pyrophosphate (FPP) by the enzyme citrus valencene synthase (CVS). Valencene can then oxidized, either biologically by a P450 or chemically, to produce nootkatone. In strains of S. cerevisiae engineered to overproduce FPP, expression of wild type CVS results in low-level production of valencene. To increase the levels, a microculture screen was developed to identify potential CVS-expressing strains with increased valencene productivity in mutant libraries. After directed mutagenesis of the CVS gene, several enzyme variants were identified using this screen. Amino acid changes were identified, and their affects on levels of expression and enzyme activity were determined. Chimeric enzymes, containing mutations from two or more variants, showed additive affects of mutations on enzyme activities. The use of these metabolic and protein engineering technologies, coupled with fermentation process development, will allow economically-viable production of nootkatone and other high-value terpenoids for the flavor and fragrance, insect repellant, and pharmaceutical markets.
Web Page: www.allylix.com
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See more of Invited Oral Papers
See more of The Annual Meeting and Exhibition 2007 (July 29 - August 2, 2007)