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Estudos de downstream processing da biomassa da microalga marinha Nannochloropsis gaditana produzida em biorreatores ao ar livre na obtenção de ácidos gordos polinsaturados e carotenoides
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Neste projeto procedeu-se ao estudo do efeito do pré-tratamento da biomassa na extração
lipídica da microalga marinha Nannochloropsis gaditana, a qual é considera uma excelente
produtora de compostos de alto valor acrescentado, como os ácidos gordos ω3 e os carotenoides.
Assim, como métodos de secagem recorreu-se à liofilização (método mais utilizado com biomassa
microalgal), à secagem na estufa e no secador solar (métodos mais sustentáveis). Como técnicas
de rutura celular foi estudado a moagem por moinho de bolas e a Homogeneização a Alta Pressão
(HPH), antes ou depois do processo da secagem. Após estes tratamentos, as amostras foram
submetidas a diferentes métodos de extração sólido-líquido: Soxhlet, Extração Acelerada por
Solventes Pressurizados (ASE, com n-hexano e etanol) e Extração com CO2 Supercrítico (SFE).
Por fim, foi feita a quantificação gravimétrica dos lípidos totais e a caracterização por
Cromatografia em Fase Gasosa com um Detetor de Ionização de Chama (GC-FID) dos ácidos
gordos e por espetrofotometria UV-Vis dos carotenoides. De todas as amostras, obtidas destas
diversas operações unitárias, verificou-se que o ácido eicosapentaenóico (EPA, 20:5ω3) foi o
ácido gordo obtido maioritariamente com percentagens de, 17 a 30 % (Soxhlet), 15 a 21 % (ASE
com n-hexano), 8 a 18 % (ASE com etanol), e 4 a 6 % (SFE). Para além do EPA, foram ainda
identificados ácidos gordos saturados e insaturados em C18 e C20, como os ácidos palmitoleico
(16:1ω7), linoleico (18:2ω6) e araquidónico (20:4ω6). Relativamente aos carotenoides totais, foi
possível identificar nos extratos, 0,002 a 0,041 % (Soxhlet), 0,002 a 0,044 % e 0,002 a 0,032 %
(ASE com n-hexano e etanol, respetivamente) e 0,05 a 0,14 % (SFE). Assim, o conjunto de prétratamentos onde se obteve maior rendimento em ácidos gordos foi a secagem na estufa, seguida
de rutura celular no moinho de bolas, com extração por ASE (n-hexano).
This project studied the effect of pre-treating biomass on the lipid extraction of the marine microalgae Nannochloropsis gaditana, which is an excellent producer of high value-added compounds such as carotenoids and ω3 polyunsaturated fatty acids. The drying methods used were freeze-drying (the most widely used method with microalgal biomass), oven drying and solar drying (the most sustainable methods). Ball milling and High-Pressure Homogenization (HPH) were studied as cell disruption techniques, either before or after the drying process. After these treatments, the samples were subjected to different solid-liquid extraction methods: Soxhlet, Accelerated Pressurised Solvent Extraction (ASE, with n-hexane and ethanol) and Supercritical CO2 Extraction (SFE). Finally, the total lipids were quantified gravimetrically, and the fatty acids were characterised by Gas Chromatography coupled to a Flame Ionisation Detector (GC-FID) and the carotenoids by UV-Vis spectrophotometry. Of all the samples obtained from these different unit operations, it was found that eicosapentaenoic acid (EPA, 20:5ω3) was the fatty acid obtained most frequently, with percentages, respectively, of 17 to 30 % (Soxhlet), 15 to 21 % (ASE with n-hexane), 8 to 18 % (ASE with ethanol), and 4 to 6 % (SFE). In addition to EPA, saturated fatty acids and unsaturated fatty acids at C18 and C20 were also identified, such as palmitoleic (16:1ω7), linoleic (18:2ω6) and arachidonic (20:4ω6) acids. Regarding total carotenoids, it was possible to identify 0.002 to 0.041 % of Soxhlet, 0.002 to 0.044 % and 0.002 to 0.032 % of ASE with n-hexane and ethanol, respectively, and 0.05 to 0.14 % of SFE in the extracts. Thus, the set of pre-treatments where the highest yield of fatty acids was obtained with oven drying, followed by cell disruption in a ball mill, and extraction by ASE (n-hexane).
This project studied the effect of pre-treating biomass on the lipid extraction of the marine microalgae Nannochloropsis gaditana, which is an excellent producer of high value-added compounds such as carotenoids and ω3 polyunsaturated fatty acids. The drying methods used were freeze-drying (the most widely used method with microalgal biomass), oven drying and solar drying (the most sustainable methods). Ball milling and High-Pressure Homogenization (HPH) were studied as cell disruption techniques, either before or after the drying process. After these treatments, the samples were subjected to different solid-liquid extraction methods: Soxhlet, Accelerated Pressurised Solvent Extraction (ASE, with n-hexane and ethanol) and Supercritical CO2 Extraction (SFE). Finally, the total lipids were quantified gravimetrically, and the fatty acids were characterised by Gas Chromatography coupled to a Flame Ionisation Detector (GC-FID) and the carotenoids by UV-Vis spectrophotometry. Of all the samples obtained from these different unit operations, it was found that eicosapentaenoic acid (EPA, 20:5ω3) was the fatty acid obtained most frequently, with percentages, respectively, of 17 to 30 % (Soxhlet), 15 to 21 % (ASE with n-hexane), 8 to 18 % (ASE with ethanol), and 4 to 6 % (SFE). In addition to EPA, saturated fatty acids and unsaturated fatty acids at C18 and C20 were also identified, such as palmitoleic (16:1ω7), linoleic (18:2ω6) and arachidonic (20:4ω6) acids. Regarding total carotenoids, it was possible to identify 0.002 to 0.041 % of Soxhlet, 0.002 to 0.044 % and 0.002 to 0.032 % of ASE with n-hexane and ethanol, respectively, and 0.05 to 0.14 % of SFE in the extracts. Thus, the set of pre-treatments where the highest yield of fatty acids was obtained with oven drying, followed by cell disruption in a ball mill, and extraction by ASE (n-hexane).
Descrição
Tese de Mestrado, Química Tecnológica, 2025, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
Nannochloropsis gaditana Ácidos gordos polinsaturados Extração de microalgas Pigmentos EPA Teses de mestrado - 2025