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- Antioxidant potential of extracts of Chromochloris zofingiensis cultivated in pilot-scale outdoor tubular photobioreactors under nitrogen limitationPublication . Corrêa, Priscila S.; M. Júnior, Wilson G. de; Caetano, NídiaChromochloris zofingiensis is known to be able to produce large amounts of astaxanthin and also to coproduce other molecules with antioxidant properties. Outdoor cultivation is the cheapest way for large-scale production; however, the unstable weather conditions can hinder the productivity of the biomass and the target product. The final biomass (0.92 g·L−1) and total carotenoids (0.55 mg·g−1) concentration achieved in outdoor cultivation (i.e., during autumn in Porto, Portugal) had no statistically significant difference compared to control cultivation (i.e., constant temperature, 18 °C, and light intensity, 4000 lx) (1.36 g·L−1 and 0.56 mg·g−1, respectively), however the biomass productivity was about threefold lower. Regarding the antioxidant potential, methanolic extracts from outdoor cultivation presented one of the highest values for radical scavenging ability (44.2 %) and ferrous-ion chelating ability (59.1 %), similarly to the results obtained by ethanolic extracts from indoor cultivation under nitrogen limitation. Highest total antioxidant capacities were observed in ethanolic extracts varying from 120.0 to 185.2 mg GAE·g−1.
- Valorização da borra de café: Recuperação de taninosPublication . Vilar, Mickael; Júnior, Wilson; Caetano, NídiaO elevado consumo mundial de café origina grande produção de resíduos. A borra (resíduo de extração) apresenta um grande potencial de contaminação devido à sua constituição (taninos, cafeína e polifenóis, entre outros compostos de elevado valor). Assim, a sua deposição, muitas vezes em condições descontroladas, representa um risco para o ambiente e perda de recursos. Neste trabalho pretendeu-se otimizar as condições de extração de taninos (composto de valor) em amostras de diferentes proveniências (cápsulas de café, borra de cafetarias, café não extraído). Os solventes testados neste trabalho foram água, acetona, metanol e etanol, tendo sido concluído que o solvente mais eficaz para a extração dos taninos foi a acetona à temperatura ambiente. A borra que apresentou uma maior abundância de taninos foi a proveniente de cápsulas, tendo sido possível recuperar 36,1 mgtaninos /100 gborra. Da borra de cafetarias húmida, extraída com etanol em 2 contactos, recuperaram-se 64,0 mgtaninos /100 gborra. O sucesso deste processo pode fomentar a redução da deposição descontrolada, com o desenvolvimento de uma indústria baseada em biorresíduos (borra), contribuindo para a criação de postos de trabalho e a produção de um bioproduto de valor, e para a dinamização da bioeconomia circular e a valorização dos biorresíduos.
- Microalgae for pigments and cosmeticsPublication . Caetano, Nídia S.; Corrêa, Priscila S.; Morais Júnior, Wilson G. de; Oliveira, Gisela M.; Martins, Antonio A.A.; Branco-Vieira, Monique; Mata, Teresa M.Microalgae are among the most promising cell factories of the near future. Their renewable nature, and ability to rely on photosynthesis to use CO2 or nutrients from wastewater to grow and multiply, make them an emergent source of valuable natural compounds. Although in the past, a few of these microalgae have been known for their value as a source of proteins, carbohydrates, exopolysaccharides, polyunsaturated fatty acids, omega 3 and omega 6 fatty acids, recently they have also been found increasingly important sources of more valuable compounds such as carotenoids, of which astaxanthin, lutein and β-carotene are of extreme importance in food, feed and cosmeceutical industries, and phycobiliproteins, chlorophylls, that are finding their place in the commercial market. There are still various challenges to be addressed to make sustainable the production of some of these valuable bioproducts. However, the circular economy and the biorefinery approach are at the center of the whole process to make the microalgae-based industry one of the most dynamic, modern and profitable industries. In this chapter it will be presented the potential microalgae sources of these valuable compounds, existing industrial applications, as well as the major ongoing research projects, and their contribution driving the blue bioeconomy.
- Microalgae Biomolecules: Extraction, Separation and Purification MethodsPublication . Corrêa, Priscila S.; Morais Júnior, Wilson Galvão; Martins, António A.; Caetano, Nídia; Mata, Teresa M.Several microalgae species have been exploited due to their great biotechnological potential for the production of a range of biomolecules that can be applied in a large variety of industrial sectors. However, the major challenge of biotechnological processes is to make them economically viable, through the production of commercially valuable compounds. Most of these compounds are accumulated inside the cells, requiring efficient technologies for their extraction, recovery and purification. Recent improvements approaching physicochemical treatments (e.g., supercritical fluid extraction, ultrasound-assisted extraction, pulsed electric fields, among others) and processes without solvents are seeking to establish sustainable and scalable technologies to obtain target products from microalgae with high efficiency and purity. This article reviews the currently available approaches reported in literature, highlighting some examples covering recent granted patents for the microalgae’s components extraction, recovery and purification, at small and large scales, in accordance with the worldwide trend of transition to bio-based products.
- Produção de biodiesel usando resíduos de pilhas alcalinas esgotadas como catalisador heterogéneoPublication . Moreira, Diogo Filipe Silva; Caetano, Nídia de Sá; Morais Júnior, Wilson GalvãoAs alterações climáticas verificadas atualmente no mundo motivam a procura de fontes de energia alternativa sustentáveis visando a substituição dos combustíveis fósseis, os principais causadores da mudança climática. Uma das soluções é a sua substituição por biocombustíveis, destacando-se o biodiesel como alternativa ao gasóleo. Na produção de biodiesel são cada vez mais usados catalisadores heterogéneos, pois reduzem o custo do processo devido à possibilidade de reutilização e geram um produto de melhor qualidade. O zinco e o manganês são componentes de catalisadores que têm apresentado alta eficiência nesta reação. Assim, foram realizados ensaios para a produção de biodiesel, utilizando a mistura catódica das pilhas alcalinas descartadas, com alta concentração de zinco e manganês. Os resultados mostram que a eficiência do uso do resíduo como catalisador na produção de biodiesel é comprovada pela obtenção de um biocombustível com densidade de 880 kg/m3, viscosidade de 4,5 mm2/s e teor de ésteres metílicos de ácidos gordos de 96,8%, conforme especificado na norma EN 14214. Assim, demonstrou- se a viabilidade técnica da utilização de um resíduo problemático (pilhas usadas) na valorização de um outro resíduo (óleo vegetal) através da produção de um biocombustível (biodiesel). Este trabalho é o primeiro registo publicado na literatura científica.
- Acid pretreatment of sugarcane biomass to obtain hemicellulosic hydrolisate rich in fermentable sugarPublication . Morais Júnior, Wilson Galvão; Pacheco, Thályta F.; Corrêa, Priscila S.; Martins, António A.; Mata, Teresa M.; Caetano, NídiaThe objective of this work was to find the ideal pretreatment conditions with high efficiency to obtain a hydrolyzate rich in fermentable sugars and low possible inhibitors levels. Thus, it was applied diluted phosphoric acid to pretreat the sugarcane biomass. Through a Central Composite Design, it was evaluated the influence of temperature, operating time and acid concentration. The pretreatment efficiency was verified by the concentration of total monosaccharides in the liquid fraction after the reaction. The phosphoric acid concentration of 4.95% at 80 °C, during 375 min, resulted in a hemicellulosic hydrolyzate with the highest concentration of fermentable sugars (saccharification greater than 99%), with the absence of HMF and furfural, and relatively low amounts of acetic acid.
- Sugarcane Bagasse Saccharification by Enzymatic Hydrolysis Using Endocellulase and β-glucosidase Immobilized on Different SupportsPublication . Morais Júnior, Wilson Galvão; Pacheco, Thályta F.; Gao, Shipeng; Martins, Pedro A.; Guisán, José M.; Caetano, NídiaThe saccharification of sugarcane bagasse by enzymatic hydrolysis is one of the most promising processes for obtaining fermentable sugar to be used in the production of second-generation ethanol. The objective of this work was to study the immobilization and stabilization of two commercial enzymes: Endocellulase (E-CELBA) in dextran coated iron oxide magnetic nanoparticles activated with aldehyde groups (DIOMNP) and β-glucosidase (E-BGOSPC) in glyoxyl agarose (GLA) so that their immobilized derivatives could be applied in the saccharification of pretreated sugarcane bagasse. This was the first time that the pretreated sugarcane bagasse was saccharified by cascade reaction using a endocellulase immobilized on dextran coated Fe2O3 with aldehyde groups combined with a β-glucosidase immobilized on glyoxyl agarose. Both enzymes were successfully immobilized (more than 60% after reduction with sodium borohydride) and presented higher thermal stability than free enzymes at 60, 70, and 80 °C. The enzymatic hydrolysis of the sugarcane bagasse was carried out with 15 U of each enzyme per gram of bagasse in a solid-liquid ratio of 1:20 for 48 h at 50 °C. Under these conditions, 39.06 ± 1.18% of the cellulose present in the pretreated bagasse was hydrolyzed, producing 14.11 ± 0.47 g/L of reducing sugars (94.54% glucose). In addition, DIOMNP endo-cellulase derivative maintained 61.40 ± 1.17% of its enzymatic activity after seven reuse cycles, and GLA β-glucosidase derivative maintained up to 58.20 ± 1.55% of its enzymatic activity after nine reuse cycles.
- LCA: A tool to develop sustainable microalgal biorefineriesPublication . Caetano, N.S.; Corrêa, P.S.; Morais Júnior, W. G.; Mata, T.M.; Martins, A.A.A.; Branco Vieira, M.Microalgae biorefineries, similar to oil refineries, are planned to exploit and maximize the value of microalgae biomass, producing as many products as possible. The biorefinery flowsheet can take different configurations, depending on the target products and the technologies to be applied. Due to the diversity of microalgae composition and strain phenotypic plasticity, some constraints can be faced for choosing the ideal candidate species. However, there are several alternatives to explore the potentiality of a strain that can make the biorefinery economically viable, environmentally friendly, and socially acceptable. Life cycle assessment (LCA) is a tool that allows evaluating the environmental impacts of a product, process, or system, and should be used to assess the environmental performance of a planned biorefinery. When combined with life cycle costing (LCC) evaluation and social life cycle assessment (S-LCA), LCA allows to take informed decisions on the most adequate biorefinery to implement. Nevertheless, and although many of the processes used in microalgae-based biorefineries are common to those used in other well-established industries, the biorefinery is an emerging area where usually novel technologies are required, some of them applied only on a pilot or a laboratory scale, making the available data limited or highly sensitive to variations. This chapter discusses the application of LCA to biorefineries, the potential hurdles, and limitations.
- Microalgae for biotechnological applications: Cultivation, harvesting and biomass processingPublication . Morais Júnior, Wilson Galvão; Gorchich, Malihe; Corrêa, Priscila S.; Martins, António A.; Mata, Teresa M.; Caetano, NídiaIn either unicellular or multi-cellular form, microalgae are photosynthetic microorganisms, mainly known for being part of the human diet in several world regions. More recently, they have been in the spotlight of researchers, not only because of their nutritional value, but also due to their high value-added components. This work reviews five microalgae genera: Dunaliella, Botryococcus, Chlamydomonas, Chlorella and Arthrospira, considered among the most promising for commercial biotechnological applications. The analysis shows that, although the research paradigms are generally shared among species, parameterization changes of culture environment and stress conditions, several applications can be envisaged for the cultivated species, which is discussed in this work. Besides, several applications in which these microalgae are being widely used, or are intended to be used, are analyzed and discussed. The potential applications depend on the type of metabolites found in each microalgae species, which is discussed in this work, giving examples of application and describing methods for their cultivation, harvesting and biomass processing. Thus, in addition to being used in human diet supplementation, microalgae can be used as ingredients for animal feed, medicines, cosmetics pigments, biofuels, bioplastics and biostimulants.