MICROALGAE AS CELL FACTORIES: RESEARCH AND INDUSTRIAL APPLICATIONS

The primary aim of this thesis is addressing the evolving industrial needs of the APG group, which has been engaged in pioneering new products and technologies in the realms of oil and green chemistry. The overarching goal is to seamlessly transition this expertise into the budding field of microalgae and the low-carbon footprint market, thereby contributing to increase the company already significant efforts to sustainability. The incessant surge in demand for microalgae-based products, particularly in the nutraceutical and cosmetic markets, necessitates a continuous cycle of development and investments to meet client demands effectively. The focal point of our efforts revolves around the enhancement of a well-established extract produced by our company known as RED. This extract, derived from the diatom P.tricornutum, is enriched with the carotenoid Fucoxanthin, renowned for its promises in various applications, including the treatment of diabetes, liver diseases, and lipid metabolism. Additionally, it exhibits substantial cosmeceutical properties, serving as an antioxidant, UV damage protector, and anti-wrinkle agent, thus encapsulating the characteristics of an innovative and grounbreaking ingredient. To realize the full potential of Fucoxanthin, our primary challenge lies in optimizing its production. A meticulous experimental plan has been devised to achieve this objective. This plan encompasses the development of a higher-yielding strain and an improved production method, optimizing both biomass production within the photobioreactors and the extract itself. The cornerstone of improving Fucoxanthin production is the purification from microbes of the original microalgae strain used in the production plant. Various isolation techniques and antibiotic mixtures have been rigorously tested to reduce the interference from other microorganisms during the inoculation process, resulting 40 in a more efficient strain performance. Further, since purified strains exhibited inadequate growth on solid substrates, extensive studies were conducted to optimize colony formation, thereby increasing the number of obtainable strains. These strains were subsequently evaluated for their Fucoxanthin content, leading to the development of a rapid analysis method using thin-layer chromatography to identify promising strains with higher Fucoxanthin content. The selected promising strains were subjected to different light spectra to assess their impact on growth and Fucoxanthin production. A two-step growth process was implemented to optimize biomass growth and Fucoxanthin accumulation. To gain a deeper understanding of the isolated morphology of the selected strain and its potential influence on growth vessel selection, a morphological study was conducted through electron microscopy. Additionally, a study on lipid droplet distribution was carried out by staining the microalgae with a fluorescent marker. Following these laboratory phases, the strains were scaled up and grown in a closed photobioreactor within the production plant, ensuring optimal conditions based on temperature, light irradiance, and mixing parameters determined during the laboratory phases. The resulting biomass underwent downstream processes, including centrifugation and freeze-drying, to remove excess water and mitigate the potential heat damage associated with heat-based water evaporation systems. The extraction process was carried on the resultin biomass powder, yielding a substantial Fucoxanthin extraction. Comprehensive analyses were conducted on the finished product, encompassing Fucoxanthin content, lipids, and the phytochemical profile of the extract. Simultaneously, the biomass was subjected to analyses for protein and lipid content. 41 The knowledge acquired during this endeavor paved the way for its application to a different microalgal strain, Tetraselmis suecica. Responding to a specific client request, we tailored the content of the alditol mannitol within the microalgae biomass. This was achieved through the manipulation of the medium composition, involving variations in salt concentrations to stress the osmotic balance in the microalgae without compromising viability. Moreover, a dedicated HPLC method for mannitol analysis was developed to support this experimental phase.