Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Agricultural Botany

Blue-green algae (cyanobacteria) have all the potential to act as a platform for the development of fourth-generation biofuel. Nevertheless, the diversity and eco-physiology of blue-green algae in northern African countries and their biofuel production potential is still understudied. The aim of this thesis was screening eight isolates of blue-green algae belonging to genera of Anabaena (A. circinalis, A. fertilissima, A. sphaerica, A. variabilis, and A. sp.) and Nostoc (N. commune, N. muscorum, and N. sp.) for high lipid productivity, and to select the best isolate to further increase its lipid induction using different treatments. The results revealed that A. sphaerica was the superior isolate with good fatty acids profile and with the highest lipids productivity which was attributed to high specific growth rate and high lipid concentration. A. sphaerica was then subjected to different treatments including culture operation mode, media duplicity as well as different nutrition strategies in terms of nutrients supplementation or elimination (i.e. two stages mode of nutrition). All studied parameters of A. sphaerica were found to be best induced by NO₃ or PO₄ elimination in two stages mode of nutrition, as well as under 60oM FeCl₃ supplementation. The environmental adaptability of A. sphaerica for lipid production under single or/and combined salt (50, 75, and 100 mM NaCl) and mild heat stress (35 {u00BA}C) was evaluated, and it was found that lipids productivity was best induced under all studied NaCl concentrations, while the 35 {u00BA}C treatment slightly increased both lipid yield and lipids % of A. sphaerica

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