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Title: Genome scale metabolic modelling of Phaeodactylum tricornutum
Author: Singh, Dipali
ISNI:       0000 0004 7430 8243
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 2017
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Diatoms are photoautotrophic unicellular algae and are among the most abundant, adaptable and diverse marine phytoplankton. Their ability to synthesise lipid as a storage compound (20%-50% dry cell weight) makes them a potential sources of biofuel and high-value commodities such as ω fatty acids. However, diatoms have unique features in their biochemistry as compared to higher plants and hence, there is a prior need to understand diatom metabolism to enable physiological and genetic manipulation, and improve their strains. The present work involves construction and analysis of genome scale metabolic models (GSMs) of Phaeodactylum tricornutum, a model diatom, the characterisation of physiological properties and the identification of the potential strategies to optimise the lipid production. GSMs were constructed based on a previously published model and metabolic databases, and were analysed using structural modelling techniques to understand the metabolic responses at different environmental and physiological conditions. The model results suggest change in metabolic responses, mainly associated with the Calvin cycle, reductant transfer, photorespiration, TCA cycle, glyoxylate cycle, lipid metabolism, carbohydrate metabolism and energy dissipation mechanisms under changing environmental and physiological conditions. Carbon xation and triose-phosphate production can take place solely in the chloroplast, despite of differences in the localisation and regulation of the Calvin cycle enzymes as compared to higher plants. Further, model analysis suggests that lipid production in P. tricornutum increases both when exposed to high light and with the availability of glycerol. The potential metabolic routes for lipid production involves phosphoketolase pathway, threonine metabolism, recycling of glycolate and HCO3 fixation. Based on the model analysis, experiments were designed where cultures were exposed to high light, supplemented with HCO3 , under phototrophic and mixotrophic conditions. This resulted to an increase in biomass and lipid productivity. In addition, by revealing the potential metabolic routes involved with lipid production, our work also suggests possible targets for metabolic engineering that could divert carbon towards lipid production.
Supervisor: Poolman, Mark ; Fell, David Sponsor: European Commission
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral