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Project Title: Directed evolution of photosystem II for light-driven biocatalysis
Summary: Photosystem II (PSII) is an enzyme, which uses light energy to split water. It achieves this fission by generating chemical species with some of the highest potentials observed in biology. Previous research has shown that PSII exhibits catalytic promiscuity by oxidising several small molecules other than water. Therefore, this enzyme represents a potential source for novel biotransformations.
Through the development and application of directed evolution and synthetic biology methods, my project aims to lay the foundations for biotechnologies that tap into this unharnessed capability for sustainable biocatalysis. Two ideas will be explored initially: The oxidation of arsenic and the oxidation of small alcohols. Arsenic(III) is a toxic compound with a detrimental effect on public health due to its presence in groundwater in several countries. It is approximately 60 times more toxic than Arsenic(V). State-of-the-art water treatment involves oxidising Arsenic(III) to Arsenic(V) prior to removal using unsustainable practices. Similarly, the oxidation of small alcohols, a process central to the chemical industry, traditionally relies on hazardous oxidising agents and energy-intensive processes.
I will use error-prone PCR and targeted random mutagenesis approaches to generate mutant libraries of D1, a core subunit of PSII, which contains the catalytic site and other redox cofactors. Then, I will be selecting and screening these libraries for enhanced oxidation of the aforementioned compounds using artificial evolutionary pressures and high-throughput screening. Promising PSII variants will be characterised using a myriad of biochemical and biophysical techniques. I will also explore applications of machine learning to enhance directed evolution.
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