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Percorrer por autor "Josenhans, Sarah"

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  • Environmental and nutritional parameters influencing the growth of Skeletonema cultures and optimization of the large-scale production in photobioreactors
    Publication . Josenhans, Sarah; Raposo, Sara; Pereira, Hugo
    Microalgae have a large variety of applications and their biomass can be produced in a sustainable way. The diatom genus Skeletonema comprises a unique biochemical composition and is already widely used in the cultivation of shrimps and molluscs. The biomass of Skeletonema strains is rich in essential biomolecules, including fucoxanthin and polyunsaturated fatty acids and hold a high market demand. However, the large-scale production of this species is still challenging and needs to be optimised. In this context, different trials were conducted from lab- to industrial-scale and the growth of Skeletonema sp. cultures was observed and evaluated. In the laboratory, using Algem® photobioreactors (PBRs), obtained results revealed that autumn conditions are favourable over winter conditions, and cultures with lower inoculum concentrations show a higher specific growth rate. In addition, an initial silicate concentration of at least 0.11 mM favours the growth of the culture and the species growth is tolerant to pH values within 7.0 to 8.5. After the lab-scale optimization, cultures were successfully scaled-up under outdoor conditions, using flat panel PBRs of 100 - 1000 L and later to tubular PBRs up to 19000 L. In the production PBRs, it was found that nutrient starvation impairs the physiological state of cultures and diluted cultures suffer from photoinhibition by radiation maxima of 1500 μmol m-² s-1. A maximal daily growth rate of 0.331 d-1 was observed in a tubular PBR, exposed to an average radiation and temperature of 521 μmol m-² s-1 and 15.24 °C, respectively. The average macronutrient composition of Skeletonema sp. biomass as percentage of dry weight was 20.88 % carbohydrates, 31.52 % proteins and 18.14 % lipids. Overall, the lab-scale optimization and large-scale production of Skeletonema was successfully achieved and the biochemical composition of the biomass seems favourable for the nutrition of aquaculture organisms.
    2019-12-16Dissertação de mestrado Acesso aberto Ver mais