Vincent Mutabiirwa Rwehumbiza

• The research objectives investigated in this project include physicochemical harvesting of Nannochloropsis salina cells from dilute culture suspensions, extraction of lipids from N. salina concentrates and their conversion to fatty acid methyl esters (FAMEs) and determination of the content of the flocculating chemicals in lipids and FAMEs. Moreover, the effect of recycling the filtrate derived from chemical flocculation of N. salina on the growth of N. salina was analyzed. Part of the work also focused on isolation and purification of polysaccharides from Porphyridium purpureum and determination of the polysaccharide’s Z-average diameters and zeta potentials and polysaccharide-matrix binding thermodynamics on selected anion exchangers. Following extraction of bioactive polysaccharide, the assay for screening antiviral efficacy of sulfated polysaccharides from the microalgae was developed after which the antiviral efficacy of partially purified metabolites was tested against dairy bacteriophages. Additionally, the extracts from P. purpureum and Isochrysis galbana were screened for antibacterial and antifungal properties. Lastly, the bacterial communities in symbiotic interaction with P. purpureum cultures were determined and studied to determine whether or not they affect polysaccharide biosynthesis by the microalgae.