Rinna, Francesca (2014) Microalgae biomass production at different growth conditions assessing the lipid content and fatty acid profile for feed, food and energy applications. [Tesi di dottorato]

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Abstract

Abstract The potential of microalgae as a source of food, feedstock and renewable energy has received considerable interest, but if microalgae production is to be economically viable and sustainable, further optimization of mass culture conditions are needed. In this work the attention was focused on the improvement of lipid productivity of two microalgae species Botryococcus braunii and Phaeodactylum tricornutum, and evaluation of lipid productivity and fatty acid profile of the cyanobacterium Arthrospira maxima, formely known as Spirulina, cultivated at the mediterranean latitudes. The thesis work consists of four experiments: 1) Growth of two strains of Botryococcus braunii (UTEX LB 572 and IB 115 ) in domestic effluents before and after pretreatment stage; 2) Effects of different environmental variables on quantity and quality of lipids of B. braunii cultivated in small and large scale; 3) Strategies to improve lipid content and fatty acid profile in Phaeodactylum tricornutum; 4) Lipid content and fatty acid profile of A. maxima cultivated in south of Italy. The two strains of B. braunii showedgood growth performances into the waste effluents with the highest value of lipid (24%) evidenced by UTEX LB 572 strain grown in influent medium. Both strains have showed a balance between saturated and unsaturated fatty acids suitable as a source of biofuel. B. braunii was shown to be capable of accumulating lipids as 65% of the biomass using nitrogen starvation, while supplying additional CO2 (3%) in the culture medium with nitrogen starvation did not improved lipid productivity. NaHCO3 as a source of C, instead of CO2, improved the -linoleic acid content of B.braunii (37±4% on total FA). -linolenic acid is important for its anti-inflammatory and immune-modulating activity and can have applications in food and feed. The lipid content and lipid productivity of P. tricornutum was significantly enhanced using nitrogen starvation. Production in ponds under greenhouse showed the highest value in EPA content (25,7%) on total FA and low production costs with high biomass productivity. The obtained results suggested that nitrogen limited algal cultivation is feasible and could be a useful strategy for producing lipid as biofuel feedstock or fatty acids for food and feed. A. maxima was grown for two years (2012-2013), from June to November, monthly evaluating lipid content and lipid profile of the obtained biomass. The mean value of lipid content in the two seasons were 8.0±3.2 and 8.3 ± 2.2 %(dw), in 2012 and 2013, respectively. The highest values was in September of both years. The lipid profile did not shown significant differences through the year and the sum of linoleic and –linolenic acids was about 50% of total FA. B. braunii and P. tricornutum cultivated, with low-cost technologies showed lipid productivityconsiderably more higher than Sunflower, Olive, Soy and Corn. A. maxima showed a lipid productivity of 0.96 t/ha/y, value close to sunflower lipid productivity 0.77t/ha/y. Thereforemicroalgae A.maxima, P.tricornutum e B.braunii are promising source of oil to be used as a functional ingredient in food industry or for the market of food supplements. These microalgae could be cultivated at our latitudes at relatively low cost of production with good nutritional characteristic

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