Browsing by Author "Mendes, Marta Sofia de Almeida"
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- Dye decolorization by yeasts : insights on pathways towards an innovative solution for textile effluentsPublication . Mendes, Marta Sofia de Almeida; Castro, Paula Maria Lima e; Pintado, Maria Manuela Estevez; Costa, Patricia Raquel Fernandes de Melo Moreira daThe textile industry produces high amounts of effluents containing synthetic dyes that are recalcitrant, toxic, potentially hazardous to the environment, and difficult to treat by conventional methods. Biotechnological approaches are generally considered more environmentally friendly and biological methods for dye degradation need to be further investigated. The work described in this PhD thesis aimed to develop a yeast-based solution to decolorize textile dyed effluents that can be safely discharged into the environment. Yeast strains Candida parapsilosis (HOMOGS20B), Yarrowia lipolytica (HOMOGST27AB) and Candida pseudoglaebosa (LIIIS36B), isolated from wastewater treatment plants, were tested for their ability to decolorize textile dyes. A total of 32 commercial textile synthetic dyes and simulated textile effluents were tested with the target yeasts (single strains and consortia) and the decolorization was evaluated spectrophotometrically for 48-72 hours. Yeasts were able to perform decolorization through adsorption and biodegradation for 28 of the dyes and simulated effluents to extents higher than 50%. Y. lipolytica (HOMOGST27AB) and C. pseudoglaebosa (LIIIS36B) presented true decolorization of reactive dyes, above 90% at 100 mg/L, and of simulated effluents at 5 g/L of concentration. Enzyme production was evaluated: oxidoreductase was found in the three yeasts, whereas tyrosinase was only found in Y. lipolytica (HOMOGST27AB) and C. pseudoglaebosa (LIIIS36B). The potential toxicity of the dyed simulated effluents, before and after treatment, was investigated. The toxicity of the yeast-treated effluents was assessed using three different assays to represent different trophic levels. Mutagenicity was also evaluated. C. pseudoglaebosa (LIIIS36B) was the most effective strain, completely decolorizing four of the five simulated effluents. Degradation products, possibly aromatic amines, were detected in the supernatant. Although the toxicity of the original simulated effluents was considered high, treated effluents demonstrated a decrease in toxicity and none exhibited mutagenicity. A yeast-based solution for decolorization of textile industrial wastewater was assessed. The three yeast strains previously selected for their dye decolorization capacity were freeze-dried. Additionally, Y. lipolytica (HOMOGST27AB) was also spray-dried. Skim milk powder and maltodextrin were used as cell protectors, and the freeze-dried products were stored at cold (4 °C) and room temperature for 210 days. The viability of the yeast cells and their decolorization capacity over time were assessed. Dried yeast cells maintained their viability and decolorization capacity for at least 90 days of storage after spray- and freeze-drying with both cell-protecting agents. The dried yeast-based solution for decolorizing textile industrial wastewater combines stability, efficiency, and convenience of production for application in real industrial facilities. A sequencing batch reactor (SBR) inoculated with activated sludge and successfully bioaugmented with the dye-decolorizing yeast strain – Y. lipolytica (HOMOGST27AB) was assembled. The bioaugmented AGS-SBR was operated for the treatment of a synthetic saline wastewater (12 g/L) intermittently fed with the reactive textile dye (Navy Everzol ED) at 25, 15, and 7.5 mg/L. Dye degradation did not occur although some dye adsorbed to the granules. AGS-SBR performance in removing carbon and nitrogen was effective and was not affected by the dye addition. The AGS core microbiome gathered essentially microorganisms from the Proteobacteria and Bacteroidetes phyla. The microbial profile showed a dynamic microbiome established at Phase I of the operation, with a high decrease in abundance of Ignavibacterium from the initial biomass to the granules formed and an increase of Actinobacteria, Cytophagia, Flavobacteria, and Alphaproteobacteria in the remaining phases of the bioreactor operation. The bioaugmented yeast remained present throughout the entire reactor process. Y. lipolytica (HOMOGST27AB) and C. pseudoglaebosa (LIIIS36B) are a potential biotechnological tool for dye degradation in textile wastewaters, especially those containing reactive dyes and a promising tool to integrate in bioremediation solutions, contributing to eco sustainability in the water sector, but further operational scenarios need to be researched.
- Functional activity of seaweed extracts from the north portuguese coastPublication . Mendes, Marta Sofia de Almeida; Gomes, Ana Maria Pereira; Carvalho, Ana Paula Santos deA utilização de algas marinhas como fontes potenciais de compostos nutracêuticos e farmacêuticos tem aumentado recentemente devido à constatação de que estas contêm compostos bioactivos, com actividades antioxidante e antimicrobiana (entre outras actividades), que podem inibir o crescimento de algumas bactérias contaminantes e/ou patogénicas e de leveduras prevenindo a deterioração de alimentos ou a infecção ou contribuindo mesmo para o seu melhor controlo. O litoral português alberga uma grande biodiversidade no que concerne a algas marinhas, porém muitas encontram-se por caracterizar em termos de propriedades funcionais. Neste contexto, o objectivo deste trabalho foi estabelecer um procedimento melhorado para a obtenção de extractos de algas marinhas e testar a sua actividade antimicrobiana contra espécies selecionadas de leveduras, bactérias Gram positivas e Gram negativas, bem como a sua actividade antioxidante. Para tentativamente atestar o seu comportamento, os perfis lipídico e fenólico foram testados. As algas utilizadas neste estudo, incluindo as de aquacultura integrada e as de habitat natural, foram obtidas no Norte de Portugal. A alga Gracilaria vermiculophylla foi usada para os ensaios de optimização do processo de extracção, enquanto as Gracilaria vermiculophylla, Porphyra dioica e Chondrus crispus foram utilizadas para os ensaios de actividade antimicrobiana e antioxidante. Os estudos de optimização centraram-se na definição dos pré-tratamentos (secagem) e da temperatura a utilizar durante o processo de extracção. Os resultados revelaram que os organismos testados foram mais sensíveis aos extractos obtidos com algas secas, continuamente processados a temperaturas mais elevadas. Posteriormente, extratos obtidos com três diferentes solventes (acetato de etilo, éter dietílico e metanol:água) foram testados. No que diz respeito à avaliação da actividade antimicrobiana, as espécies testadas incluíram (i) bactérias Gram negativas - Escherichia coli, Salmonella enteritidis e Pseudomonas aeruginosa; (ii) bactérias Gram positivas – Listeria innocua, Bacillus cereus, Enterococcus faecalis, Lactobacillus brevis, Staphylococcus aureus, todas de origem alimentar, e uma estirpe de Staphylococcus aureus de origem clínica, e (iii) a levedura Candida spp. também de origem clinica. Os testes para avaliar a actividade antimicrobiana dos extractos foram realizados utilizando o método de difusão em agar e os resultados indicaram uma forte actividade antimicrobiana dos extractos de acetato de etilo, quando comparado com os extractos de metanol e éter dietílico e mostraram uma tendência fraca para a inibição de microrganismos Gram positivos. O perfil de ácidos gordos de extractos de acetato de etilo revelou uma predominância de ácidos gordos saturados (SFA), especialmente o acido palmítico (16:0), seguido por ácidos gordos polinsaturados (PUFA) e ácidos gordos monoinsaturados (MUFA) e mostrou um teor mais elevado de ácidos gordos em G. vermiculophylla e P. dioica de aquacultura. Tendo em conta os resultados obtidos para a actividade antioxidante, foi demonstrado que os extractos metanólicos apresentaram actividade mais elevada quando comparada com os outros solventes testados. O perfil fenólico revelou que os extractos metanólicos mostraram quantidades mais elevadas de compostos fenólicos, tais como catequinas e ácido protocatecuico, o que pode indiciar o seu papel na actividade antioxidante.