Enrichment of bioactive compounds in microalgae for aquaculture

Microalgae are promising microorganisms for the production of food and fine chemicals. Several species of microalgae are used in aquaculture with the purpose of transfer bioactive compounds up to the aquatic food chain. The main objective of this project was to develop a stress–inducement strategy in order to enhance the biochemical productivity of Nannochloropsis gaditana, Rhodomonas marina and Isochrysis sp. for aquaculture purposes having in account their growth and organizational differences. In this regard, two experiments were design: the first one consisted on the alteration of overall nutrient availabilities in growth medium; and the second one comprised changes in nitrogen and sulfur concentrations maintaining the concentrations of the other nutrients present in a commercial growth medium (Nutribloom plus), which is frequently used in aquaculture. Microalgae dried biomass was characterized biochemically and elemental analysis was also performed for all samples. In first experimental design: linear trends between nutrient availability in growth media and microalgae protein content were obtained; optimum productivities of eicosapentaenoic (EPA) and docosahexaenoic acids (DHA) were attained for both R. marina and N. gaditana in growth media enriched with 1000 L L-1 of nutrient solution whereas for Isochrysis sp. the double of Nutribloom plus was needed; the decrease of glucans and total monosaccharides with nutrient availability for R. marina and Isochrysis sp. showed the occurrence of a possible depletion of carbohydrates towards lipids and proteins biosynthesis. Second experimental desing: N. gaditana exhibited the highest variation in their biochemical composition against the applied perturbation; variations observed for microalgae in their biochemical composition were reflected in their elemental stoichiometry; in N. gaditana the highest nitrogen concentrations lead to overall maximum productivities of the biochemical parameters. The results of the present work show two stress-inducement strategies for microalgae that may constitute a base for further investigations on their biochemical enhancement

Exploring Pavlova pinguis and Hemiselmis cf. andersenii as natural sources of high-value lipids

A crescente demanda dos consumidores por fontes naturais e sustentáveis de compostos de valor acrescentado tem levado as comunidades científica e industrial a explorar a biodiversidade das microalgas e a sua diversidade química. Na bioprospecção de microalgas para a produção integrada de biomassa e compostos de valor acrescentado, diversos desafios são encontrados, como o cultivo de novas espécies, a identificação de novas moléculas e a otimização das condições de cultivo para a produção dos fitoquímicos desejados. Este estudo investiga o potencial de duas microalgas inexploradas, Hemiselmis cf. andersenii e Pavlova pinguis, como fontes de lípidos com valor acrescentado para aplicação na indústria nutracêutica e áreas relacionadas. A análise dos extratos lipídicos revelou uma grande diversidade de metabolitos sintetizados pela H. cf. andersenii e pela P. pinguis, nomeadamente ácidos gordos, esteróis, álcoois e monoglicerídeos. H. cf. andersenii demonstrou ser rica em ómega-3 polinsaturados. Enquanto, a P. pinguis revelou ser uma grande produtora de fitoesteróis. Para verificar a robustez das microalgas e induzir a acumulação dos compostos desejados, foram realizados estudos com diferente suplementação de azoto e de fósforo no meio de crescimento das microalgas. As condições repletas de azoto revelaram-se eficazes para modelar a composição lipídica das microalgas para as indústrias nutracêutica e farmacêutica. Aumentos dos teores de fósforo induziram um aumento da produtividade da biomassa e da produção de lípidos nutricionalmente relevantes. Na P. pinguis, baixos teores de fósforo mostraram-se eficazes para a produção de carotenoides e açúcares. A H. cf. andersenii mostrou-se promissora para a coprodução de carotenoides e lípidos. A análise multivariada permitiu visualizar os efeitos intra e interespecíficos dos nutrientes na composição lipídica das microalgas. A grande versatilidade de compostos de valor acrescentado produzidos pelas microalgas estudadas aliadas às suas características biológicas (ausência de parede celular rígida), fazem destas candidatas promissoras para futura produção à escala industrial.The active seek of consumers for natural sustainable sources of high-value compounds has driven the scientific and industry communities to exploit microalgal biodiversity and its intrinsic chemical diversity. In the bioprospection of microalgae for integrated biomass and high value compounds production, several challenges are found, like the cultivation of new species, the identification of new molecules, and the optimization of culture conditions to produce the desired phytochemicals. The present work aimed to investigate the potential of two unexplored microalgae, Hemiselmis cf. andersenii e Pavlova pinguis, as sources of high-value lipids for further application in nutraceutical and other related fields. The detailed analysis of lipid extracts revealed a great diversity of metabolites synthesized by H. cf. andersenii and P. pinguis, namely fatty acids, sterols, alcohols, and monoglycerides. H. cf. andersenii was shown to be a rich source of omega-3 polyunsaturated fatty acids. Meanwhile, P. pinguis was found to be a high level producer of phytosterols. To evaluate the robustness of the microalgae and induce its production on high-value lipids, experiments were performed by inducing changes in nitrogen and phosphorus levels in microalgae growth medium. In both microalgae nitrogen-replete conditions were the most effective for modeling the lipid composition for nutraceutical and pharmaceutical industries. Increases in phosphorus concentrations prompted an increase in microalgal biomass productivity, as well as the production of nutritionally relevant lipids. In P. pinguis, low phosphorus concentrations were effective to produce carotenoids and sugars. H. cf. andersenii have shown to be suitable for the co-production of carotenoids and lipids. Multivariate analysis allowed to visualize the differential intra- and inter- specific effects of nitrogen and phosphorus on microalgal lipid composition. The great versatility of value-added compounds produced by the studied microalgae combined with its biological properties (absence of a rigid cell wall) make these microalgae promising candidates for future large-scale production