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- Otto, Maximilian, 1991
(author)
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Combining Metabolic Engineering and Synthetic Biology Approaches for the Production of Abscisic Acid in Yeast
- 2023
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Doctoral thesis (other academic/artistic)abstract
- Nature presents us with a myriad of complex and diverse molecules. Many of these molecules prove to be useful to humans and find applications as pharmaceuticals, biofuels, agrochemicals, cosmetic ingredients or food additives. One highly promising natural product with a broad range of potential applications is the terpenoid abscisic acid (ABA). ABA fulfils a pivotal role in higher plants by regulating various developmental processes as well as abiotic stress responses. However, ABA is also produced in many other organisms, including humans. It appears to be a ubiquitous and evolutionary conserved signalling molecule throughout nature. Genetically engineered microorganisms, referred to as microbial cell factories, can be a sustainable source of natural products. In this thesis, a cell factory for the heterologous production of ABA was established and optimized employing the yeast Saccharomyces cerevisiae. Cell factory development is an inherently time-consuming process. As an enabling technology for subsequent work on the ABA cell factory, we expanded the modular cloning toolkit for yeast and made it more applicable for common genetic engineering tasks (Paper I). The ABA biosynthetic pathway of Botrytis cinerea was used to construct an ABA-producing S. cerevisiae strain (Paper II). The activity of two B. cinerea proteins, BcABA1 and BcABA2, was found to limit ABA titers. Two optimization approaches were devised for the following studies. Firstly, various rational engineering targets were explored, of which the native yeast gene PAH1 was identified as the most promising candidate (Paper III). Knockdown of PAH1 benefited ABA production without affecting growth. Secondly, platform strains for screening BcABA1 and BcABA2 enzyme libraries were developed, which utilize an ABA biosensor and enable a high throughput screening approach (Paper IV). In this work, we combined metabolic engineering and synthetic biology approaches for the heterologous production of ABA, and furthermore provided tools and insights that will be useful beyond the scope of this project.
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| 2. |
- Otto, Maximilian, 1991, et al.
(author)
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Expansion of the Yeast Modular Cloning Toolkit for CRISPR-Based Applications, Genomic Integrations and Combinatorial Libraries
- 2021
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In: ACS Synthetic Biology. - : American Chemical Society (ACS). - 2161-5063. ; 10:12, s. 3461-3474
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Journal article (peer-reviewed)abstract
- Standardisation of genetic parts has become a topic of increasing interest over the last decades. The promise of simplifying molecular cloning procedures, while at the same time making them more predictable and reproducible has led to the design of several biological standards, one of which is modular cloning (MoClo). The Yeast MoClo toolkit provides a large library of characterised genetic parts combined with a comprehensive and flexible assembly strategy. Here we aimed to (1) simplify the adoption of the standard by providing a simple design tool for including new parts in the MoClo library, (2) characterise the toolkit further by demonstrating the impact of a BglII site in promoter parts on protein expression, and (3) expand the toolkit to enable efficient construction of gRNA arrays, marker-less integration cassettes and combinatorial libraries. These additions make the toolkit more applicable for common engineering tasks and will further promote its adoption in the yeast biological engineering community.
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| 3. |
- Otto, Maximilian, 1991, et al.
(author)
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Integration of a multi-step heterologous pathway in Saccharomyces cerevisiae for the production of abscisic acid
- 2019
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In: Microbial Cell Factories. - : Springer Science and Business Media LLC. - 1475-2859. ; 18:1
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Journal article (peer-reviewed)abstract
- Background: The sesquiterpenoid abscisic acid (ABA) is mostly known for regulating developmental processes and abiotic stress responses in higher plants. Recent studies show that ABA also exhibits a variety of pharmacological activities. Affordable and sustainable production will be required to utilize the compound in agriculture and as a potential pharmaceutical. Saccharomyces cerevisiae is an established workhorse for the biotechnological production of chemicals. In this study, we constructed and characterised an ABA-producing S. cerevisiae strain using the ABA biosynthetic pathway from Botrytis cinerea. Results: Expression of the B. cinerea genes bcaba1, bcaba2, bcaba3 and bcaba4 was sufficient to establish ABA production in the heterologous host. We characterised the ABA-producing strain further by monitoring ABA production over time and, since the pathway contains two cytochrome P450 enzymes, by investigating the effects of overexpressing the native S. cerevisiae or the B. cinerea cytochrome P450 reductase. Both, overexpression of the native or heterologous cytochrome P450 reductase, led to increased ABA titres. We were able to show that ABA production was not affected by precursor or NADPH supply, which suggested that the heterologous enzymes were limiting the flux towards the product. The B. cinerea cytochrome P450 monooxygenases BcABA1 and BcABA2 were identified as pathway bottlenecks and balancing the expression levels of the pathway enzymes resulted in 4.1-fold increased ABA titres while reducing by-product formation. Conclusion: This work represents the first step towards a heterologous ABA cell factory for the commercially relevant sesquiterpenoid. © 2019 The Author(s).
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| 4. |
- Otto, Maximilian, 1991, et al.
(author)
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Saccharomyces cerevisiae as a Heterologous Host for Natural Products
- 2022
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In: Methods in Molecular Biology. - New York, NY : Springer US. - 1940-6029 .- 1064-3745. ; 2489, s. 333-367
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Book chapter (other academic/artistic)abstract
- Cell factories can provide a sustainable supply of natural products with applications as pharmaceuticals, food-additives or biofuels. Besides being an important model organism for eukaryotic systems, Saccharomyces cerevisiae is used as a chassis for the heterologous production of natural products. Its success as a cell factory can be attributed to the vast knowledge accumulated over decades of research, its overall ease of engineering and its robustness. Many methods and toolkits have been developed by the yeast metabolic engineering community with the aim of simplifying and accelerating the engineering process.In this chapter, a range of methodologies are highlighted, which can be used to develop novel natural product cell factories or to improve titer, rate and yields of an existing cell factory with the goal of developing an industrially relevant strain. The addressed topics are applicable for different stages of a cell factory engineering project and include the choice of a natural product platform strain, expression cassette design for heterologous or native genes, basic and advanced genetic engineering strategies, and library screening methods using biosensors. The many engineering methods available and the examples of yeast cell factories underline the importance and future potential of this host for industrial production of natural products.
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| 5. |
- Pereira, Rui, 1986, et al.
(author)
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Metabolic Engineering of Yeast
- 2021
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In: Metabolic Engineering: Concepts and Applications: Volume 13a and 13b. - : Wiley. ; 13, s. 689-733
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Book chapter (other academic/artistic)abstract
- This chapter focuses on a few examples that can serve as illustrations of how powerful yeast metabolic engineering stands today. Yeast, especially S. cerevisiae, plays an essential role in bioethanol production. Rapid ethanol production by yeast cells makes the fermentation process less susceptible to contamination. Higher alcohols are attractive due to some advantages compared with bioethanol, such as higher energy density, better blending into gasoline, higher octane value, lower hygroscopicity, and less corrosivity. The ethanol production process in the industry is mainly achieved through simultaneous saccharification and fermentation. Production of insulin, by volume the largest pharmaceutical protein produced, has paved the way for a wide use of S. cerevisiae for production of recombinant proteins. Virus like particles are proteins of virus capsid, which are produced by recombinant DNA technology and are important for the development of viral vaccines as they can self-assemble and display similar immunogenic properties as native viruses.
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