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Increased ethylene production by overexpressing phosphoenolpyruvate carboxylase in the cyanobacterium Synechocystis PCC 6803
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. (Mikrobiell kemi)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. (Mikrobiell kemi)ORCID iD: 0000-0002-6413-1443
Natl Renewable Energy Lab, Biosci Ctr, Golden, CO USA.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. (Mikrobiell kemi)ORCID iD: 0000-0001-7256-0275
2020 (English)In: Biotechnology for Biofuels, ISSN 1754-6834, E-ISSN 1754-6834, Vol. 13, article id 16Article in journal (Refereed) Published
Abstract [en]

Background: Cyanobacteria can be metabolically engineered to convert CO2 to fuels and chemicals such as ethylene. A major challenge in such efforts is to optimize carbon fixation and partition towards target molecules.

Results: The efe gene encoding an ethylene-forming enzyme was introduced into a strain of the cyanobacterium Synechocystis PCC 6803 with increased phosphoenolpyruvate carboxylase (PEPc) levels. The resulting engineered strain (CD-P) showed significantly increased ethylene production (10.5 +/- 3.1 mu g mL(-1) OD-1 day(-1)) compared to the control strain (6.4 +/- 1.4 mu g mL(-1) OD-1 day(-1)). Interestingly, extra copies of the native pepc or the heterologous expression of PEPc from the cyanobacterium Synechococcus PCC 7002 (Synechococcus) in the CD-P, increased ethylene production (19.2 +/- 1.3 and 18.3 +/- 3.3 mu g mL(-1) OD-1 day(-1), respectively) when the cells were treated with the acetyl-CoA carboxylase inhibitor, cycloxydim. A heterologous expression of phosphoenolpyruvate synthase (PPSA) from Synechococcus in the CD-P also increased ethylene production (16.77 +/- 4.48 mu g mL(-1) OD-1 day(-1)) showing differences in the regulation of the native and the PPSA from Synechococcus in Synechocystis.

Conclusions: This work demonstrates that genetic rewiring of cyanobacterial central carbon metabolism can enhance carbon supply to the TCA cycle and thereby further increase ethylene production.

Place, publisher, year, edition, pages
2020. Vol. 13, article id 16
National Category
Microbiology
Identifiers
URN: urn:nbn:se:uu:diva-392232DOI: 10.1186/s13068-020-1653-yISI: 000513591700001PubMedID: 32010220OAI: oai:DiVA.org:uu-392232DiVA, id: diva2:1347569
Funder
NordForsk, 82845Available from: 2019-09-01 Created: 2019-09-01 Last updated: 2020-03-25Bibliographically approved
In thesis
1. Increased Carbon Fixation for Chemical Production in Cyanobacteria
Open this publication in new window or tab >>Increased Carbon Fixation for Chemical Production in Cyanobacteria
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The combustion of fossil fuels has created many environmental problems, the major one, the greenhouse effect. Thus, we need solutions in order to replace fossil fuels and recycle the CO2 in the atmosphere. Renewable energies have created attention the last decades but electricity is the main energy form obtained. Photosynthetic organisms (including cyanobacteria) can be used as cell factories since they can convert solar energy to chemical energy. In addition, the requisites to grow them are few; light water, CO2 and inorganic nutrients. Cyanobacteria have been genetically engineered in order to produce numerous chemicals and fuels of human interest in direct processes. However, the amount of product obtained is still low. Increased carbon fixation in cyanobacteria results in higher production of carbon-based substances. This thesis focuses on the effects of overexpressing the native phosphoenolpyruvate carboxylase (PEPc) in the model cyanobacterium Synechocystis PCC 6803. PEPc is an essential enzyme and provides oxaloacetate, an intermediate of the tricarboxylic acid cycle (TCA cycle). The TCA cycle is involved in connecting the carbon and nitrogen metabolism in cyanobacteria. The strains were further engineered to produce ethylene and succinate, two examples of interests for the chemical and fuel industry. Strains with additional PEPc produced significantly more ethylene and succinate. Moreover, an in vitro characterization of PEPc from the cyanobacterium Synechococcus PCC 7002 was performed. The focus was on oligomerization state, kinetics and the structure of the carboxylase. This thesis demonstrates that increasing carbon fixation and discovering the bottlenecks in chemical production can lead to higher yields and gives us hope that cyanobacteria can be commercialized.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 65
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1848
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-392234 (URN)978-91-513-0736-7 (ISBN)
Public defence
2019-10-18, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2019-09-25 Created: 2019-09-01 Last updated: 2019-10-15

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