Screening, mutagenesis and gene expression analysis for improving fucoxanthin biosynthesis in the marine diatom Phaeodactylum tricornutum.
- Publication Type:
- Thesis
- Issue Date:
- 2023
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Advancements in agricultural technology have been a prevailing feature of exponential human population growth since the Neolithic revolution 5. Plants have long been recognised as providers of vital services in the form of food, raw materials, and compounds for health 6.
However, there is a growing appreciation of the need to transform current agricultural practices that are strongly associated with high water demand, pollution of soil and waterways, and biodiversity loss 7,8.
Microalgae harbour enormous potential as sustainable contributors to a wide array of industries and technologies, including the production of useful molecules for health and food, sequestration of atmospheric carbon, wastewater treatment, and production of sustainable biofuels 9,10.
This thesis is focused on the marine diatom Phaeodactylum tricornutum as a production platform for the primary carotenoid fucoxanthin, which is a pigment currently used in the food and pharmaceutical sectors 11. Each chapter represents proof of concept studies for, and betters understanding of, critical areas of microalgae biotechnology – high-throughput screening, untargeted mutagenesis, artificial selection and gene expression for pigment biosynthesis.
In Chapter 1, a reliable, inexpensive, and fast high-throughput screening method was developed for detecting fucoxanthin in P. tricornutum. In Chapter 2, three mutagens were evaluated for the ability to increase fucoxanthin in P. tricornutum mutants. Fluctuating pigment content detected over six months in three mutant lines and one strain displaying a 35% increase in fucoxanthin at four months highlighted the critical need for temporal phenotype stability for studies of this kind. In Chapter 3, a FACS-based method was used to artificially isolate a population of P. tricornutum with increased growth, pigment content, and fucoxanthin productivity under an industry-relevant culturing regime. Additionally, gene expression analysis and gene pathway enrichment analysis were used to highlight genes of potential interest to chlorophyll and fucoxanthin biosynthesis. It was found that the tetrapyrrole pathway was significantly enriched and likely responsible for upregulated chlorophyll, while only three genes along the carotenoid pathway were upregulated, indicating only a few critical rate-limiting steps in fucoxanthin biosynthesis.
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