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Abstract(s)
A biotecnologia das microalgas está a ganhar cada vez mais importância, havendo já um número significativo de estudos publicados. Contudo, a grande maioria dos trabalhos realizados continua a ser com macroalgas. A maior parte dos estudos com macro- e microalgas têm, contudo, uma base empírica, relacionada com os organismos congéneres que são as plantas vasculares.
No trabalho apresentado nesta Tese revemos inicialmente algumas das aplicações das microalgas, em especial as de origem marinha. Após uma resenha sobre os polissacarídeos (capítulo 1.1), focamo-nos na aplicação (potencial) dos biocompostos na saúde humana, em geral (capítulo 1.2) e nas doenças cardiovasculares, em particular (capítulo 1.3) e ainda em doenças crónicas como as relacionadas com o stress oxidativo, a diabetes ou o Parkinson, devido às suas propriedades antioxidantes.
Em seguida, aprofundamos o conhecimento sobre os polissacáridos algais (capítulo 2). Neste capítulo, revemos as características bioquímicas deste tipo de polímeros e mostramos algumas das vastas aplicações dos polissacáridos produzidos pelas microalgas (capítulo 2.1). Mostramos ainda quão abrangente pode ser a utilização destes compostos, quer em aplicações médicas (capítulo 2.2), quer em nutrição, devido à sua riqueza em fibras (capítulo 2.3).
Sabendo que duas das espécies produtoras de elevadas quantidades de carotenoides são a Dunaliella salina e a Haematococcus pluvialis, desenvolvemos um primeiro trabalho experimental em que os respectivos meios de cultura foram enriquecidos com as fito-hormonas cinetina (kin) e ácido diclorofenoxiacético (2,4-D) (capítulo 3.1). A influência positiva de 2,4-D foi bastante significativa, dado que a adição de 1.0 mg /l meio de cultura de H. pluvialis, sózinha ou em conjunto com kin (1.0 mg /l), aumentou a produção de biomassa em 320% e 290% respectivamente. Uma ainda menor concentração de 2,4-D (0.5 mg /l) induziu, em D. salina (a 15% salinidade, NaCl m/v), um aumento de 410% no número de células. Num trabalho experimental posterior submeteu-se a Haematococcus a condições de stress (privação de nutrientes e luminosidade elevada) para indução da carotenogénese. A biomassa foi depois recolhida e procurou-se a melhor forma de manter a estabilidade dos carotenoides produzidos e uma taxa de degradação mais reduzida. As melhores condições de preservação verificaram-se quando se secou as algas por atomização (temperatura de entrada de 180ºC e temperatura de saída de 110ºC) e armazenamento dos pós a -21ºC em azoto. Desta forma conseguiu-se recuperar 90% do pigmento astaxantina (capítulo 4). Quando se manipulou o meio de cultura de Porphyridium cruentum, verificou-se que a adição de sulfato (21 mM em sulfato) aumentou a produção do exopolissacárido (EPS), e o conteúdo em proteína (52 mM e 104 mM em sulfato) e sulfato (104 mM) no EPS. Contudo, as características físico-químicas do polímero não sofreram alterações. Este EPS mostrou possuir capacidade antiviral, em especial contra o vírus Vesicular estomatitis (capítulo 3.2).
Duas experiências diferentes permitiram mostrar que as microalgas têm também aplicação na área ambiental (capítulo 5). Verificou-se que a flora autóctone de um efluente de cervejeira pode ser utilizada para remoção de grande parte do azoto e fósforo, mas também para remover uma parte significativa da carga orgânica dessa água residual. Devido à qualidade da proteína obtida — na qual se observou um aumento de vários aminoácidos essenciais — e do perfil lipídico da biomassa — tendo-se verificado um aumento de alguns ácidos gordos como o ácido eicosapentaenóico (ou EPA) —, a biomassa final pode ser recolhida e eventualmente utilizada em rações para animais, ou ainda para produção de biodiesel (capítulo 5.1). Numa última experiência testou-se a influência da utilização das microalgas, tanto sozinhas como em consórcio com rizobactérias promotoras do crescimento, no melhoramento dos solos. Os pós das algas Chlorella vulgaris e/ou dos consórcios obtidos por atomização foram também incluídos em microcápsulas revestidas por maltodextrina (MD) e goma-arábica (GA) ou gelatina (G). Os consórcios de Chlorella:Stenotrophomonas encapsulados em MD:G e MD:GA 1:1 (m/m) foram os que induziram um melhor crescimento, em termos de biomassa seca, tanto da raiz, como da parte aérea das plantas utilizadas neste estudo (capítulo 5.2).
Resumindo, pensamos que, com estes trabalhos, contribuímos para o aumento do conhecimento em biotecnologia de microalgas e teremos talvez alertado para o grande potencial das microalgas, especialmente as de origem marinha, devido à sua grande variedade e riqueza da sua biomassa em compostos bioactivos.
The biotechnology of microalgae is gaining more and more importance, and a significant number of studies is already published. However, the vast majority of the work has been performed with macroalgae. Nonetheless, most of the studies with macro- and microalgae have an empirical basis, relating to the counterpart organisms, which are vascular plants. In the beginning of the work presented in this thesis, we reviewed some of the applications of microalgae, especially the ones of marine origin. After reviewing the literature on polysaccharides (chapter 1.1), we focused on the (potential) application of the biocompounds from microalgae in human health, in general (chapter 1.2), and in the cardiovascular diseases, in particular (chapter 1.3). We also focused on the applications in chronic diseases, such as those related to the oxidative stress, like diabetes or Parkinson, due to the antioxidant properties of such compounds. Then, we went deeper into the knowledge of the polysaccharides (chapter 2). In this chapter, we reviewed the biochemical characteristics of this type of polymers, and showed some of the vast applications of the polysaccharides produced by microalgae (chapter 2.1). We showed as well how broad the uses of these compounds may be, both in medical uses (chapter 2.2) and in nutrition, due to being rich in fibre (chapter 2.3). Considering that the two species producing high amounts of carotenoids are Dunaliella salina and Haematococcus pluvialis, we developed a first experimental work on which the respective culture media were enriched with phytohormones kinetin (Kin) and dichlorophenoxyacetic acid (2,4-D) (chapter 3.1). The positive influence of 2,4-D was very significant, as the addition of 1.0 mg /l culture of H. pluvialis, alone or combined with Kin (1.0 mg /l), enhanced the production of biomass in 320% and 290%, respectively. An even lower concentration of 2,4-D (0.5 mg /l) induced an increase of 410% in the D. salina cell number (under 15% salinity, NaCl w/v). In further experimental work, we subjected Haematococcus to stress conditions (deprivation of nutrients and high brightness) to induce carotenogenesis. After collecting the carotenized biomass, we looked for the best conditions in order to maintain the stability of the produced carotenoids, with a lower degradation ratio. The best preservation conditions after spray-drying the biomass (inlet temperature of 180ºC and outlet temperature of 110ºC) showed to be the storage of the dried powders in nitrogen at -21ºC. A 90% of astaxanthin recovery was obtained at these conditions (chapter 4). During the manipulation of the Porphyridium cruentum culture medium, we verified that the addition of sulphate (21 mM in sulphate) increased the production of the exopolysaccharide (EPS), and also the protein (52 mM and 104 mM in sulphate) and sulphate content (104 mM) of the EPS. However, the physicochemical characteristics of the polymer did not suffer any modifications. This EPS showed to have antiviral properties, particularly against Vesicular stomatitis virus (chapter 3.2). Two different experiments allowed us to show that microalgae may also find application in the environmental area (chapter 5). We verified that the autochthonous flora from the effluent of a brewery might be used to remove the majority of the nitrogen and phosphorus, and also a significant part of the organic load of that wastewater. Due to the quality of the protein – where we observed an increase in several essential aminoacids — and the lipid profile of the biomass – where it was observed an increase in some fatty acids, such as eicosapentaenoic acid (EPA) —, the final biomass may be harvested and eventually used in animal feed, or to produce biodiesel (chapter 5.1). In the last experiment, we studied the influence of the use of microalgae, alone or as a consortium with growth-promoting rhizobacteria (GPRB), on soil improvement. Spray-dried powders from the alga Chlorella vulgaris and/or the consortia were also included into microcapsules coated with maltodextrin (MD) and arabic gum (GA) or gelatin (G). The consortia Chlorella:Stenotrophomonas encapsulated in MD:G and MD:GA 1:1 (w/w) were the ones that induced a higher growth, considering the dried biomass, of both the roots and the shoots of the plants used in this study (chapter 5.2). In summary, we think that, through these studies and experimental work, we have contributed to the enhancement of the knowledge in the biotechnology of microalgae and we have, at least, drawn the attention to the great potential of microalgae, particularly those from marine sources, due to their vast diversity and richness of their biomass in bioactive compounds.
The biotechnology of microalgae is gaining more and more importance, and a significant number of studies is already published. However, the vast majority of the work has been performed with macroalgae. Nonetheless, most of the studies with macro- and microalgae have an empirical basis, relating to the counterpart organisms, which are vascular plants. In the beginning of the work presented in this thesis, we reviewed some of the applications of microalgae, especially the ones of marine origin. After reviewing the literature on polysaccharides (chapter 1.1), we focused on the (potential) application of the biocompounds from microalgae in human health, in general (chapter 1.2), and in the cardiovascular diseases, in particular (chapter 1.3). We also focused on the applications in chronic diseases, such as those related to the oxidative stress, like diabetes or Parkinson, due to the antioxidant properties of such compounds. Then, we went deeper into the knowledge of the polysaccharides (chapter 2). In this chapter, we reviewed the biochemical characteristics of this type of polymers, and showed some of the vast applications of the polysaccharides produced by microalgae (chapter 2.1). We showed as well how broad the uses of these compounds may be, both in medical uses (chapter 2.2) and in nutrition, due to being rich in fibre (chapter 2.3). Considering that the two species producing high amounts of carotenoids are Dunaliella salina and Haematococcus pluvialis, we developed a first experimental work on which the respective culture media were enriched with phytohormones kinetin (Kin) and dichlorophenoxyacetic acid (2,4-D) (chapter 3.1). The positive influence of 2,4-D was very significant, as the addition of 1.0 mg /l culture of H. pluvialis, alone or combined with Kin (1.0 mg /l), enhanced the production of biomass in 320% and 290%, respectively. An even lower concentration of 2,4-D (0.5 mg /l) induced an increase of 410% in the D. salina cell number (under 15% salinity, NaCl w/v). In further experimental work, we subjected Haematococcus to stress conditions (deprivation of nutrients and high brightness) to induce carotenogenesis. After collecting the carotenized biomass, we looked for the best conditions in order to maintain the stability of the produced carotenoids, with a lower degradation ratio. The best preservation conditions after spray-drying the biomass (inlet temperature of 180ºC and outlet temperature of 110ºC) showed to be the storage of the dried powders in nitrogen at -21ºC. A 90% of astaxanthin recovery was obtained at these conditions (chapter 4). During the manipulation of the Porphyridium cruentum culture medium, we verified that the addition of sulphate (21 mM in sulphate) increased the production of the exopolysaccharide (EPS), and also the protein (52 mM and 104 mM in sulphate) and sulphate content (104 mM) of the EPS. However, the physicochemical characteristics of the polymer did not suffer any modifications. This EPS showed to have antiviral properties, particularly against Vesicular stomatitis virus (chapter 3.2). Two different experiments allowed us to show that microalgae may also find application in the environmental area (chapter 5). We verified that the autochthonous flora from the effluent of a brewery might be used to remove the majority of the nitrogen and phosphorus, and also a significant part of the organic load of that wastewater. Due to the quality of the protein – where we observed an increase in several essential aminoacids — and the lipid profile of the biomass – where it was observed an increase in some fatty acids, such as eicosapentaenoic acid (EPA) —, the final biomass may be harvested and eventually used in animal feed, or to produce biodiesel (chapter 5.1). In the last experiment, we studied the influence of the use of microalgae, alone or as a consortium with growth-promoting rhizobacteria (GPRB), on soil improvement. Spray-dried powders from the alga Chlorella vulgaris and/or the consortia were also included into microcapsules coated with maltodextrin (MD) and arabic gum (GA) or gelatin (G). The consortia Chlorella:Stenotrophomonas encapsulated in MD:G and MD:GA 1:1 (w/w) were the ones that induced a higher growth, considering the dried biomass, of both the roots and the shoots of the plants used in this study (chapter 5.2). In summary, we think that, through these studies and experimental work, we have contributed to the enhancement of the knowledge in the biotechnology of microalgae and we have, at least, drawn the attention to the great potential of microalgae, particularly those from marine sources, due to their vast diversity and richness of their biomass in bioactive compounds.
Description
Keywords
Biotecnologia de microalgas Chlorella Cianobactérias Dunaliella Haematococcus Porphyridium Polissacáridos Carotenoides Compostos bioactivos Biotechnology of microalgae Cyanobacteria Polysaccharides Carotenoids Bioactive compounds