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- Studies on Hydrogen Sulfide Oxidase from Pseudomonas sp.Publication . Novo, Ana; Antunes, Filipa; Baptista, Inês; Jorge, Ruben; Saraiva, Isabel; Moreira, Irina S.; Castro, Paula M. L.
- Development of sustainable processes for obtaining lignin from sugarcane by-products and its valorisationPublication . Antunes, Filipa Alexandre Soares Gomes; Costa, Patrícia Filipa Santos; Mota, Maria Inês Ferreira da; Burgal, João Porfírio da SilvaThe sugarcane industry generates several by-products, including straw (SCS) and bagasse (SCB). Their conversion into value-added products is of the utmost importance from a circular economy perspective. Lignin - one of the three main components of biomasses - has attracted considerable interest as a versatile ingredient for different applications. Therefore, this thesis aims to valorise, in a sustainable way, sugarcane residues (SCS and SCB), through the development of lignin-based products. In Chapter 1, it is presented a literature review focused on the valorisation of lignin obtained from sugarcane by-products. In Chapter 2, the detailed objectives of the project are presented. Chapter 3 presents different pre-treatments for lignin extraction, namely, alkaline, organosolv and deep eutectic solvents (DES). Furthermore, the combination of pretreatments was carried out following an integrated process approach: hydrothermal pretreatment followed by an alkaline pretreatment. The alkaline pretreatment of SCB proved to be the most effective among all pretreatments, producing lignin with distinct properties, such as purity (89%), colour (light brown; L*/a*/b*: 60.3/6.1/19.1), odour (woody sweet) and production cost (29 €/kg). Regarding sustainability, all processes achieved excellent scores ranging from 83 to 93%, with the alkaline extraction achieving the highest value. Chapter 4 describes the purification of the lignin obtained with lower purity. In this context, the alkaline liquor from the SCS was subjected to a two-stage membrane filtration step: first the liquor was filtered with a polyvinylidene fluoride microfiltration membrane (500-1000 kDa), followed by filtration with a 10 kDa polyethersulfone ultrafiltration membrane to concentrate the permeate flux. After acid precipitation at pH 2, the lignin purity increased from 61% to 84%. Chapter 5 details the characterisation of the lignins obtained by the pre-treatments in terms of physicochemical and structural properties. The results confirmed the presence of the main functional groups in the seven lignins, with some differences attributed to the biomass. The highest content of total hydroxyl phenolic units was obtained for the organosolv SCB and integrated process lignins. It was also concluded that guaiacyl (G) units were predominant in the SCB pretreatments, followed by syringyl (S) units. The organosolv lignin showed lower molecular weight, while the highest molecular weight distribution was observed for the SCS lignins with DES and alkaline pretreatments. In Chapter 6, the antioxidant and antibacterial activities of the SCB and SCS lignins from the different optimised pretreatments were evaluated, and the relationship between chemical structure and lignin functionality was elucidated. The total phenolic content and antioxidant activity were significantly higher for the alkaline, organosolv and integrated process SCS and SCB lignins. Regarding the antibacterial activity, the alkaline lignins showed activity against both representative bacteria evaluated (Escherichia coli and Staphylococcus aureus), with the SCB alkaline lignin showing the best performance. Chapter 7 explores the development of two products in the areas of cosmetics and materials. For the cosmetics field, lignin was tested as a natural UV blocker, antioxidant, and pigment in an blemish balm (BB) cream formulation. Remarkable results were achieved in terms of in vitro and in vivo SPF of 9.5 ± 2.9 and 9.6 ± 0.8, respectively. Furthermore, the lignin-based BB cream showed a broad-spectrum UV protection (critical wavelength 378 ± 0.5 nm). Lignin also showed antioxidant capacity after incorporation, being safe for topical applications. For materials, lignin was explored as a waterproofing agent in coatings for cardboard packaging. The results showed that the lignin-based coating was able to increase the water resistance of paper by up to three times, suggesting that this coating is a promising solution to improve the performance of paper-based packaging. The coating also demonstrated resistance to cracking by 90° folding. The results of this study corroborate the potential of sugarcane residues as a natural and sustainable source of new ingredients for the development of innovative lignin-based products.
- Valorization of mushroom by-products as a source of value-added compounds and potential applicationsPublication . Antunes, Filipa; Marçal, Sara; Oludemi, Taofiq; Morais, Alcina M. M. B.; Freitas, Ana Cristina; Ferreira, Isabel C. F. R.; Pintado, ManuelaNowadays, the food sector is highly concerned with environmental issues and foreseen to develop strategies to reduce waste and losses resulting from activities developed in the food system. An approach is to increment added value to the agro-industrial wastes, which might provide economic growth and environmental protection, contributing to a circular economy. Mushroom by-products represent a disposal problem, but they are also promising sources of important compounds, which may be used due to their functional and nutritional properties. Research has been developed in diferent fields to obtain value added solutions for the by-products generated during mushroom production and processing. Bioactive compounds have been obtained and applied in the development of nutraceutical and pharmaceutical formulations. Additionally, other applications have been explored and include animal feed, fertilizer, bioremediation, energy production, bio-based materials, cosmetics and cosmeceuticals. The main purpose of this review is to highlight the relevant composition of mushroom by-products and discuss their potential as a source of functional compounds and other applications. Future research needs to explore pilot and industrial scale extraction methods to understand the technological feasibility and the economic sustainability of the bioactive compounds extraction and valorization towards diferent applications.
- Hydrogen sulfide biological oxidation by pure cultures of heterotrophic bacteriaPublication . Novo, Ana; Antunes, Filipa; Baptista, Inês; Jorge, Ruben; Saraiva, Isabel; Moreira, Irina S.; Castro, Paula M. L.Biogas is a mixture of gases produced during anaerobic treatment of sludge whose composition depends on the type of digested materials as well as on the operating conditions of bioreactor. This consists mainly of CH4 and CO2, but components such as H2S is of particular interest due to its corrosive, toxic and environmentally hazardous properties. Removal of H2S present in biogas can be achieved through physical and chemical processes, which are effective but produce secondary waste, which in turn gives rise to another problem of pollution. Biological treatment can be used to removing H2S using different species of microorganisms whose specific enzymes catalyze the biological oxidation of H2S, including photoautotrophic and chemotrophs organisms. This work aims to compare the biotechnological removal of H2S from biogas in aerobic conditions through heterotrophic microbial biomass and biocatalytic treatments. Heterotrophic microorganisms were isolated from microbial enrichments supplied with H2S streams from a wastewater treatment plant and were characterized based on their ability to grow in mineral medium with acetate as source of carbon. Isolates retrieved were mainly affiliated to the class of γ-proteobacteria with a strong prevalence of the genus Pseudomonas. Isolates A9, B9 and C1 all identified as Pseudomonas spp., revealed as the species with higher potential for H2S removal, growing at concentrations of H2S up to 16 mM. Total protein profiles were screened by SDS-PAGE for the three isolates, before and after the addition of H2S, with the aim of purifying enzyme fractions involved in the oxidation process.
- Bacterial nanocellulose membranes loaded with vitamin B-based ionic liquids for dermal care applicationsPublication . Chantereau, G.; Sharma, M.; Abednejad, A.; Vilela, C.; Costa, E. M.; Veiga, M.; Antunes, F.; Pintado, M. M.; Sèbe, G.; Coma, V.; Freire, M. G.; Freire, C. S. R.; Silvestre, A. J. D.The development of innovative bio-based skin care products has received an increase attention in the latter years. In the present work, the synthesis of original active principle ingredients based ionic liquids (ILs) with cholinium cation and vitamins B anions followed by their incorporation in bacterial nanocellulose (BC) membranes for topical applications is reported. Three ILs, namely cholinium nicotinate [Ch][B3], cholinium pantothenate [Ch][B5] and cholinium pyridoxylate [Ch][B6], were synthesized through a metathesis reaction and their structure characterized in detail. Thermal analysis confirmed their denomination as ILs and their high thermal resistance. The solubility of these ILs was higher than their vitamin precursors, especially in the case of [Ch][B3] whose solubility increased 30.6-fold enhancing the bioavailability of this vitamin. The incorporation of ILs in BC led to transparent and homogeneous membranes stable up to 190 °C. ILs acted as plasticizers reducing BC brittleness that facilitated their application on irregular skin regions. Moreover, the re-hydration ability of BC-ILs membranes was improved 2.9 to 4.8-fold in comparison to BC, ensuring adequate hydration for ILs release, while the release of ILs in buffer solutions was more complete and faster than the release of vitamins. Finally, BC-ILs were proven not cytotoxic to skin epithelial cells and thus are suitable materials for skin care applications.
- In vitro intestinal absorption of amino acid mixtures extracted from codfish (Gadus morhua L.) salting wastewaterPublication . Ferraro, Vincenza; Jorge, Ruben Ferreira; Cruz, Isabel B.; Antunes, Filipa; Sarmento, Bruno; Castro, Paula M. L.; Pintado, Manuela E.This study reports on the intestinal permeability of salt-containing mixtures of amino acids extracted from codfish salting wastewater. Permeability was evaluated in vitro using the Caco-2 cell line model; cell integrity during exposure to mixtures of amino acids was estimated by measuring the transepithelial electrical resistance (TEER). The effect of salt (NaCl) on the permeability and on the intestinal cell’s integrity was also examined. Permeation rate (i.e. transport) was ≥95% for all amino acids except for creatine, for which it was 6%. Values for apparent permeability coefficients, Papp > 10 5 cm s 1, for mixture with isotonic concentration of NaCl suggest that amino acids are very likely to be absorbed in humans. Mixture with a hypertonic level of NaCl exerts a cytotoxic effect in intestinal cells resulting in a loss of epithelium integrity. Results show that isotonic mixture of amino acids extracted from codfish salting wastewater could be used in food, feed, cosmetic and pharmaceutical formulations. These applications could contribute to the fish industry sustainability.