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Efficient bio-production of citramalate using an engineered Escherichia coli strain

Webb, Joseph P.; Arnold, S. Alison; Baxter, Scott; Hall, Stephen J.; Eastham, Graham; Stephens, Gill

Authors

Joseph P. Webb

S. Alison Arnold

Scott Baxter

Stephen J. Hall

Graham Eastham

Gill Stephens



Abstract

Citramalic acid is a central intermediate in a combined biocatalytic and chemocatalytic route to produce bio-based methylmethacrylate, the monomer used to manufacture Perspex and other high performance materials. We developed an engineered E. coli strain and a fed-batch bioprocess to produce citramalate at concentrations in excess of 80 g l-1 in only 65 h. This exceptional efficiency was achieved by designing the production strain and the fermentation system to operate synergistically. Thus, a single gene encoding a mesophilic variant of citramalate synthase from Methanococcus jannaschii, CimA3.7, was expressed in E. coli to convert acetyl-CoA and pyruvate to citramalate, and the ldhA and pflB genes were deleted. By using a bioprocess with a continuous, growth-limiting feed of glucose, these simple interventions diverted substrate flux directly from central metabolism towards formation of citramalate, without problematic accumulation of acetate. Furthermore, the nutritional requirements of the production strain could be satisfied through the use of a mineral salts medium supplemented only with glucose (172 g l-1 in total) and 1.4 g l-1 yeast extract. Using this system, citramalate accumulated to 82±1.5 g l-1, with a productivity of 1.85 g l-1 h-1 and a conversion efficiency of 0.48 gcitramalate g-1 glucose. The new bioprocess forms a practical first step for integrated bio- and chemocatalytic production of methylmethacrylate.

Citation

Webb, J. P., Arnold, S. A., Baxter, S., Hall, S. J., Eastham, G., & Stephens, G. (2018). Efficient bio-production of citramalate using an engineered Escherichia coli strain. Microbiology, 164(2), 133-141. https://doi.org/10.1099/mic.0.000581

Journal Article Type Article
Acceptance Date Nov 15, 2017
Online Publication Date Dec 12, 2017
Publication Date Feb 1, 2018
Deposit Date Nov 28, 2017
Publicly Available Date Mar 28, 2024
Journal Microbiology
Electronic ISSN 1465-2080
Publisher Microbiology Society
Peer Reviewed Peer Reviewed
Volume 164
Issue 2
Pages 133-141
DOI https://doi.org/10.1099/mic.0.000581
Keywords citramalic acid; methyl methacrylate; fed-batch fermentation; bio-based chemicals
Public URL https://nottingham-repository.worktribe.com/output/909583
Publisher URL http://mic.microbiologyresearch.org/content/journal/micro/10.1099/mic.0.000581

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