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Germann AT, Nakielski A, Dietsch M, Petzel T, Moser D, Triesch S, Westhoff P, Axmann IM. A systematic overexpression approach reveals native targets to increase squalene production in Synechocystis sp. PCC 6803. Front Plant Sci 2023; 14:1024981. [PMID: 37324717 PMCID: PMC10266222 DOI: 10.3389/fpls.2023.1024981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 04/28/2023] [Indexed: 06/17/2023]
Abstract
Cyanobacteria are a promising platform for the production of the triterpene squalene (C30), a precursor for all plant and animal sterols, and a highly attractive intermediate towards triterpenoids, a large group of secondary plant metabolites. Synechocystis sp. PCC 6803 natively produces squalene from CO2 through the MEP pathway. Based on the predictions of a constraint-based metabolic model, we took a systematic overexpression approach to quantify native Synechocystis gene's impact on squalene production in a squalene-hopene cyclase gene knock-out strain (Δshc). Our in silico analysis revealed an increased flux through the Calvin-Benson-Bassham cycle in the Δshc mutant compared to the wildtype, including the pentose phosphate pathway, as well as lower glycolysis, while the tricarboxylic acid cycle predicted to be downregulated. Further, all enzymes of the MEP pathway and terpenoid synthesis, as well as enzymes from the central carbon metabolism, Gap2, Tpi and PyrK, were predicted to positively contribute to squalene production upon their overexpression. Each identified target gene was integrated into the genome of Synechocystis Δshc under the control of the rhamnose-inducible promoter Prha. Squalene production was increased in an inducer concentration dependent manner through the overexpression of most predicted genes, which are genes of the MEP pathway, ispH, ispE, and idi, leading to the greatest improvements. Moreover, we were able to overexpress the native squalene synthase gene (sqs) in Synechocystis Δshc, which reached the highest production titer of 13.72 mg l-1 reported for squalene in Synechocystis sp. PCC 6803 so far, thereby providing a promising and sustainable platform for triterpene production.
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Affiliation(s)
- Anna T. Germann
- Institute for Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Andreas Nakielski
- Institute for Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Maximilian Dietsch
- Institute for Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Tim Petzel
- Institute for Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Daniel Moser
- Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany
| | - Sebastian Triesch
- Institute of Plant Biochemistry, Cluster of Excellence on Plant Science (CEPLAS), Heinrich Heine University, Düsseldorf, Germany
| | - Philipp Westhoff
- Plant Metabolism and Metabolomics Laboratory, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Ilka M. Axmann
- Institute for Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
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Barone GD, Cernava T, Ullmann J, Liu J, Lio E, Germann AT, Nakielski A, Russo DA, Chavkin T, Knufmann K, Tripodi F, Coccetti P, Secundo F, Fu P, Pfleger B, Axmann IM, Lindblad P. Recent developments in the production and utilization of photosynthetic microorganisms for food applications. Heliyon 2023; 9:e14708. [PMID: 37151658 PMCID: PMC10161259 DOI: 10.1016/j.heliyon.2023.e14708] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 03/08/2023] [Accepted: 03/15/2023] [Indexed: 05/09/2023] Open
Abstract
The growing use of photosynthetic microorganisms for food and food-related applications is driving related biotechnology research forward. Increasing consumer acceptance, high sustainability, demand of eco-friendly sources for food, and considerable global economic concern are among the main factors to enhance the focus on the novel foods. In the cases of not toxic strains, photosynthetic microorganisms not only provide a source of sustainable nutrients but are also potentially healthy. Several published studies showed that microalgae are sources of accessible protein and fatty acids. More than 400 manuscripts were published per year in the last 4 years. Furthermore, industrial approaches utilizing these microorganisms are resulting in new jobs and services. This is in line with the global strategy for bioeconomy that aims to support sustainable development of bio-based sectors. Despite the recognized potential of the microalgal biomass value chain, significant knowledge gaps still exist especially regarding their optimized production and utilization. This review highlights the potential of microalgae and cyanobacteria for food and food-related applications as well as their market size. The chosen topics also include advanced production as mixed microbial communities, production of high-value biomolecules, photoproduction of terpenoid flavoring compounds, their utilization for sustainable agriculture, application as source of nutrients in space, and a comparison with heterotrophic microorganisms like yeast to better evaluate their advantages over existing nutrient sources. This comprehensive assessment should stimulate further interest in this highly relevant research topic.
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Affiliation(s)
- Giovanni D. Barone
- Institute of Molecular Biotechnology, Graz University of Technology, Petersgasse 14, 8010, Graz, Austria
- Corresponding author.
| | - Tomislav Cernava
- Institute of Environmental Biotechnology, Graz University of Technology, Petersgasse 12/I, 8010, Graz, Austria
| | - Jörg Ullmann
- Roquette Klötze GmbH & Co. KG, Lockstedter Chaussee 1, D-38486, Klötze, Germany
| | - Jing Liu
- State Key Laboratory of Marine Resource Utilization in South China Sea Hainan University, 58 Renmin Avenue, Meilan District, Haikou, Hainan Province, 570228, PR China
| | - Elia Lio
- Institute of Chemical Sciences and Technologies (SCITEC) “Giulio Natta” Italian National Research Council (CNR), via Mario Bianco 9, 20131, Milan, Italy
| | - Anna T. Germann
- Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - Andreas Nakielski
- Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
| | - David A. Russo
- Friedrich Schiller University Jena, Institute for Inorganic and Analytical Chemistry, Bioorganic Analytics, Lessingstr. 8, D-07743, Jena, Germany
| | - Ted Chavkin
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | | | - Farida Tripodi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126, Milano, Italy
| | - Paola Coccetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126, Milano, Italy
| | - Francesco Secundo
- Institute of Chemical Sciences and Technologies (SCITEC) “Giulio Natta” Italian National Research Council (CNR), via Mario Bianco 9, 20131, Milan, Italy
| | - Pengcheng Fu
- State Key Laboratory of Marine Resource Utilization in South China Sea Hainan University, 58 Renmin Avenue, Meilan District, Haikou, Hainan Province, 570228, PR China
| | - Brian Pfleger
- Knufmann GmbH, Bergstraße 23, D-38486, Klötze, Germany
| | - Ilka M. Axmann
- Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany
- Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University Düsseldorf, D-40001, Düsseldorf, Germany
- Corresponding author. Synthetic Microbiology, Department of Biology, Heinrich Heine University Düsseldorf, 40225, Düsseldorf, Germany.
| | - Peter Lindblad
- Microbial Chemistry, Department of Chemistry–Ångström, Uppsala University, Box 523, SE-75120, Uppsala, Sweden
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Abstract
Design and implementation of synthetic biological circuits highly depends on well-characterized, robust promoters with predictable input-output responses. While great progress has been made with heterotrophic model organisms such as Escherichia coli, the available variety of tunable promoter parts for phototrophic cyanobacteria is still limited. Commonly used synthetic and semisynthetic promoters show weak dynamic ranges or no regulation at all in cyanobacterial models. Well-controlled alternatives such as native metal-responsive promoters, however, pose the problems of inducer toxicity and lacking orthogonality. Here, we present the comparative assessment of dose-response functions of four different inducible promoter systems in the model cyanobacterium Synechocystis sp. PCC 6803. Using the novel bimodular reporter plasmid pSHDY, dose-response dynamics of the re-established vanillate-inducible promoter PvanCC was compared to the previously described rhamnose-inducible Prha, the anhydrotetracycline-inducible PL03, and the Co2+-inducible PcoaT. We estimate individual advantages and disadvantages regarding dynamic range and strength of each promoter, also in comparison with well-established constitutive systems. We observed a delicate balance between transcription factor toxicity and sufficient expression to obtain a dose-dependent response to the inducer. In summary, we expand the current understanding and employability of inducible promoters in cyanobacteria, facilitating the scalability and robustness of synthetic regulatory network designs and of complex metabolic pathway engineering strategies.
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Affiliation(s)
- Anna Behle
- Institute for Synthetic Microbiology, Heinrich Heine University Duesseldorf, 40225 Duesseldorf, Germany
| | - Pia Saake
- Institute for Synthetic Microbiology, Heinrich Heine University Duesseldorf, 40225 Duesseldorf, Germany
| | - Anna T. Germann
- Institute for Synthetic Microbiology, Heinrich Heine University Duesseldorf, 40225 Duesseldorf, Germany
| | - Dennis Dienst
- Department of Chemistry − Ångström, Uppsala University, 75120 Uppsala, Sweden
| | - Ilka M. Axmann
- Institute for Synthetic Microbiology, Heinrich Heine University Duesseldorf, 40225 Duesseldorf, Germany
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