CIM1-Teses
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- Heterotrophic cultivation of Thraustochytrids using glycerol and saline medium from a dairy effluentPublication . Fortes, Luís André Roque; Raposo, SaraMicroalgae are a promising source of biofuels and other valuable chemicals. The reduced economic feasibility of microalgal cultures is due to low cell density and slow growth rate of these cultures. Thus, it is necessary to develop sustainable processes that will be able to increase the productivity, maximize the production yield and reduce production costs. To achieve this goals, it is necessary to improve the understanding of the behavior of microalgal cultures. A robust method was developed for the growth of Thraustochytrids in saline waste medium using glycerol as carbon source. The first study case was the heterotrophic cultivation of Schizochytrium limacinum in order to achieve the highest growth and DHA content possible using alternative raw materials. In the second study case, the temperature profiles of Japanochytrium sp. were analyzed to identify the optimal temperature for growth and PUFAs production. The first case study, Schizochytrium limacinum was grown in saline waste medium using glycerol as carbon source. After 216 hours of fermentation the values obtained were the following: biomass concentration of 40.4 g.L-1, DHA content of 48.5% and a DHA productivity of 424 mg.L-1.d-1. The results obtained proved that Schizochytrium limacinum. is able to grow and produce high levels of DHA using saline waste medium and glycerol as carbon source. Besides, it was made the economic balance of the used media for biomass and DHA production. In standard medium to produce 1 kg of biomass and 1 kg of DHA will cost 105 € and 1.235 €, respectively. While in saline waste medium to produce 1 kg of biomass and 1 kg of DHA will cost 17.16 € and 180.7 €, respectively. The second case study, Japanochytrium sp. was cultivated at different temperatures of 15, 20, 25 and 30 ˚ C. The highest value of biomass, 22 g.L-1, was obtained at 25 ˚C whereas the lowest value of biomass, 11 g.L-1, was obtained at 15 ˚C. For 20 ˚C and 30 ˚C the biomass concentration was 19 g.L-1 and 16 g.L-1, respectively. These results are in agreement with the literature, where the optimal temperature to the growth of thraustochytrids range between 22-28 ˚C. Glycerol is the major byproduct of the biodiesel industry and since it is expensive to purify, biodiesel producers must seek alternative methods for its disposal. Hence using glycerol as a carbon source for fermentation is an alternative use for this product.