n-Butanol production in Saccharomyces cerevisiae is limited by the availability of coenzyme A and cytosolic acetyl-CoA
- Background: Butanol isomers are regarded as more suitable fuel substitutes than bioethanol. n-Butanol is naturally produced by some Clostridia species, but due to inherent problems with clostridial fermentations, industrially more relevant organisms have been genetically engineered for n-butanol production. Although the yeast Saccharomyces cerevisiae holds significant advantages in terms of scalable industrial fermentation, n-butanol yields and titers obtained so far are only low. Results: Here we report a thorough analysis and significant improvements of n-butanol production from glucose with yeast via the acetoacetyl-CoA-derived pathway. First, we established an improved n-butanol pathway by testing various isoenzymes of different pathway reactions. This resulted in n-butanol titers around 15 mg/L in synthetic medium after 74 h. As the initial substrate of the n-butanol pathway is acetyl-coenzyme A (acetyl-CoA) and most intermediates are bound to coenzyme A (CoA), we increased CoA synthesis by overexpression of the pantothenate kinase coaA gene from Escherichia coli. Supplementation with pantothenate increased n-butanol production up to 34 mg/L. Additional reduction of ethanol formation by deletion of alcohol dehydrogenase genes ADH1-5 led to n-butanol titers of 71 mg/L. Further expression of a mutant form of an ATP independent acetylating acetaldehyde dehydrogenase, adhEA267T/E568K, converting acetaldehyde into acetyl-CoA, resulted in 95 mg/L n-butanol. In the final strain, the n-butanol pathway genes, coaA and adhE A267T/E568K, were stably integrated into the yeast genome, thereby deleting another alcohol dehydrogenase gene, ADH6, and GPD2-encoding glycerol-3-phosphate dehydrogenase. This led to a further decrease in ethanol and glycerol by-product formation and elevated redox power in the form of NADH. With the addition of pantothenate, this strain produced n-butanol up to a titer of 130 ± 20 mg/L and a yield of 0.012 g/g glucose. These are the highest values reported so far for S. cerevisiae in synthetic medium via an acetoacetyl-CoA-derived n-butanol pathway. Conclusions: By gradually increasing substrate supply and redox power in the form of CoA, acetyl-CoA, and NADH, and decreasing ethanol and glycerol formation, we could stepwise increase n-butanol production in S. cerevisiae. However, still further bottlenecks in the n-butanol pathway must be deciphered and improved for industrially relevant n-butanol production levels.
Author: | Virginia SchadewegGND, Eckhard BolesORCiD |
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URN: | urn:nbn:de:hebis:30:3-440304 |
DOI: | https://doi.org/10.1186/s13068-016-0456-7 |
ISSN: | 1754-6834 |
Pubmed Id: | https://pubmed.ncbi.nlm.nih.gov/26913077 |
Parent Title (English): | Biotechnology for biofuels |
Publisher: | BioMed Central |
Place of publication: | London |
Document Type: | Article |
Language: | English |
Date of Publication (online): | 2017/05/22 |
Year of first Publication: | 2016 |
Publishing Institution: | Universitätsbibliothek Johann Christian Senckenberg |
Release Date: | 2017/05/22 |
Tag: | ABE fermentation; Coenzyme A; Pantothenate; Saccharomyces; acetyl-CoA; n-butanol |
Volume: | 9 |
Issue: | Art. 44 |
Page Number: | 12 |
First Page: | 1 |
Last Page: | 12 |
Note: | Copyright: © Schadeweg and Boles 2016. Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. |
HeBIS-PPN: | 425198316 |
Institutes: | Biowissenschaften / Biowissenschaften |
Dewey Decimal Classification: | 5 Naturwissenschaften und Mathematik / 57 Biowissenschaften; Biologie / 570 Biowissenschaften; Biologie |
Sammlungen: | Universitätspublikationen |
Open-Access-Publikationsfonds: | Biowissenschaften |
Licence (German): | Creative Commons - Namensnennung 4.0 |