Assessing the suitability of Pleurochrysis and associated strains, for simultaneous biofuel production and carbon capture
Pleurochrysis and Chrysotila are coccolithophorid algae (Haptophycea), which are mainly marine unicellular phytoplankton. The coccolithophorids are of global interest as they can fix carbon by photosynthesis, as well forming calcium carbonate coccoliths. They are the largest carbon sinks and one of the largest primary producers of biomass on the planet, with their ancestors being responsible for the deposition of large quantities of chalk. They can also produce high amounts of lipids, which have a high potential application as a renewable fuel and alternative food source. The objective of this study was to investigate the suitability of different strains of Pleurochrysis and Chrysotila for simultaneous biofuel production and carbon capture, and to explore the potential of a biorefinery approach to achieve this. The initial twelve strains provided by the Culture Collection of Algae and Protozoa (CCAP) were assessed for their morphological characteristics, in order to assess their suitability for further experimentation. Subsequently, growth optimisation was then performed on a variety of different species, as well as isolates that had not been identified to species level. These included Pleurochrysis sp. CCAP 944/4, Chrysotila carterae CCAP 944/6, Chrysotila carterae CCAP 961/2, Chrysotila carterae CCAP 961/1, Chrysotila carterae CCAP 961/4, Chrysotila carterae CCAP 961/5 and Chrysotila carterae CCAP 961/8. Further experimentation was then undertaken to the assess the potential of carbon sequestration via calcite formation within these cells. Understanding the process in which carbon is incorporated into the cells and understanding the conditions that promoted the production of extracellular coccoliths became key when understanding the conditions in which these coccoliths detach from the cells. Cells were assessed via scanning electron microscopy (SEM) and subjected to different environmental stresses to induce the removal of coccoliths. The most productive strains were then analysed to assess lipid quantities and dry weight of biomassby using standard methods of lipid extractions. Samples were then subjected to gas chromatography (GC) analysis to understand the composition of their lipids and suitability for biofuel production. An overall summary to assess the potential of using a biorefinery approach to sequester CO2 and produce lipids was discussed in the final chapter. This includes the comparison of pond systems and bioreactors, as well as utilising the coccoliths produced by cells which could then be applied to environmental engineering procedures. This in turn could be a significant tool for geochemical and environmental engineering as a way of managing climate change.
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