Metabolic engineering of Escherichia coli for production of valerenadiene.

Abstract

Valeriana officinalis is a medicinal herb which produces a suite of compounds in its root tissue useful for treatment of anxiety and insomnia. The sesquiterpene components of the root extract, valerenic acid and valerena-1,10-diene, are thought to contribute to most of the observed anxiolytic of Valerian root preparations. However, valerenic acid and its biosynthetic intermediates are only produced in low quantities in the roots of V. officinalis. Thus, in this report, Escherichia coli was metabolically engineered to produce substantial quantities of valerena-1,10-diene in shake flask fermentations with decane overlay. Expression of the wildtype valerenadiene synthase gene (pZE-wvds) resulted in production of 12μg/mL in LB cultures using endogenous FPP metabolism. Expression of a codon-optimized version of the valerenadiene synthase gene (pZE-cvds) resulted in 3-fold higher titers of valerenadiene (32μg/mL). Co-expression of pZE-cvds with an engineered methyl erythritol phosphate (MEP) pathway improved valerenadiene titers 65-fold to 2.09mg/L valerenadiene. Optimization of the fermentation medium to include glycerol supplementation enhanced yields by another 5.5-fold (11.0mg/L valerenadiene). The highest production of valerenadiene resulted from engineering the codon-optimized valerenadiene synthase gene under strong Ptrc and PT7 promoters and via co-expression of an exogenous mevalonate (MVA) pathway. These efforts resulted in an E. coli production strain that produced 62.0mg/L valerenadiene (19.4mg/L/OD600 specific productivity). This E. coli production platform will serve as the foundation for the synthesis of novel valerenic acid analogues potentially useful for the treatment of anxiety disorders.

• Authors: S Eric Nybo, Jacqueline Saunders, Sean P McCormick
• Journal: Journal of biotechnology (J Biotechnol) Vol. 262 Pg. 60-66 (Nov 20 2017) ISSN: 1873-4863 [Electronic] Netherlands
• PMID: 28988031 (Publication Type: Journal Article)
• Copyright: Copyright © 2017 Elsevier B.V. All rights reserved.

Chemical References

• Codon
• Indenes
• Sesquiterpenes
• Sesquiterpenes, Guaiane
• Viral Proteins
• valerenadiene
• valerenic acid
• valerenal
• bacteriophage T7 RNA polymerase
• DNA-Directed RNA Polymerases
• Glycerol
• Erythritol
• Mevalonic Acid

Topics

• Codon
• DNA-Directed RNA Polymerases (genetics)
• Erythritol
• Escherichia coli (genetics, metabolism)
• Fermentation
• Gene Expression Regulation, Bacterial
• Genetic Vectors
• Glycerol (metabolism)
• Indenes (metabolism)
• Metabolic Engineering
• Metabolic Networks and Pathways (genetics)
• Mevalonic Acid (metabolism)
• Promoter Regions, Genetic
• Saccharomyces cerevisiae (metabolism)
• Sesquiterpenes (chemistry, metabolism)
• Sesquiterpenes, Guaiane
• Valerian (genetics)
• Viral Proteins (genetics)