Biomass productivity enhancement and extraction of high values products of an extremophile microalga from SCCA culture collection

The main objectives of the Ph.D. thesis were: i. to characterize the growth of Coccomyxa melkonianii SCCA 048 for the production of high-value bio-products, such as lipids; ii. to investigate the growth and lipids production kinetics of the microalga, and the optimization of its biomass production as well as its lipids productivity in qualitative-quantitative terms; iii. to identify the best cultivation strategies of the selected strain for enhanced production of biomass and high-value compounds, with viable exploitation in large-scale plants (Raceways) for several biotechnological applications. Coccomyxa melkonianii SCCA 048, belonging to the Sardinian Culture Collection of Algae (SCCA), is a green extremophile microalga found in a mine drainage habitat and characterized by the ability to live in highly selective environments with extreme conditions, such as high concentrations of heavy metals. This strain has been already elected for its rich carotenoids profile. These features make C. melkonianii SCCA 048 a very promising strain for cultivation in economic open ponds and for the production of high-value products if cultivated under a suitable cultivation strategy. The thesis research aimed to optimize the production of biomass and to study the effect of pH and nitrogen concentration on lipid composition. After the identification and contextualization of the research topic, supported by updated scientific literature, the thesis identifies the effects of the selected parameters on the production of biomass and lipid content in quantitative and qualitative terms. The results identify the optimal pH and nitrogen values for biomass production and highlight the productive potential of the Sardinian microalga C. melkonianii. Furthermore, the research acquired new information on the physiology of this strain, which constitutes a fundamental prerequisite for any future project that foresees the use of the organism on a large scale.