Extracção de lactato com membranas líquidas

Dissertação apresentada para obtenção do grau de Doutor em Engenharia Química, especialidade Fenómenos de Transferência pela Universidade Nova de Lisboa,Faculdade de Ciências e TecnologiaNeste trabalho estudou-se o processo de extracção/reextracção de lactato usando diversas configurações de membranas líquidas: membrana líquida, membrana líquida suportada e contactor de membranas. Na configuração mais simples, a membrana líquida é constituída apenas pela fase orgânica que contém o extraente enquanto as outras duas contêm adicionalmente uma membrana polimérica como suporte da fase orgânica. Foi seleccionado como extraente um sal de uma amina quaternária(Aliquat 336) de modo a tomar os processos de remoção e produção de ácido láctico por fermentação, compatíveis a nível de pH. Foi desenvolvido um modelo de equilíbrio, usando a constante de equilíbrio da reacção de permuta iónica entre a amina e o lactato, que permite a previsão da concentração de lactato no equilíbrio para diferentes condições experimentais. Foram identificados outros mecanismos envolvidos no processo de transporte quando se usam membranas líquidas e diferentes concentrações iniciais de lactato e de cloreto, nos compartimentos de alimentação e de reextracção. Do estudo cinético efectuado concluiu-se que o passo limitante no processo de transferência de massa é a resistência oferecida pela fase orgânica no interior dos poros da membrana suporte. De modo a reduzir a resistência da membrana é necessário aumentar o coeficiente de difusão do complexo lactato-amina, aumentando a temperatura ou reduzindo a concentração de extraente. Na configuração membrana líquida suportada verificou-se uma progressiva perda de eficiência no transporte de lactato ao longo do tempo. O contactor de fibras ocas revelou-se a configuração mais adequada uma vez que foi obtida uma grande estabilidade operacional e ausência de emulsões. Devido à elevada área de transferência por volume de módulo foi também obtida uma grande velocidade de transferência de soluto. Foi ainda estudado o processo integrado de fermentação e de extracção / reextracção de lactato do qual se pôde concluir que a amina quaternária (Aliquat 336) tem um carácter muito tóxico para o microrganismo usado, mesmo em concentrações inferiores às de saturação. O uso de membranas pode ser vantajoso, uma vez que evita a formação de emulsões e retarda a perda de extraente para o meio de fermentação.G.B.F. - Gesellschaft für Biotechnologische Forschung, JNICT - Junta Nacional de Investigação Científica e Tecnológica, Projecto SlRDA/ /CEN/701/9

Concentration of tea extracts by osmotic evaporation: optimisation of process parameters and effect on antioxidant activity

In this work, the concentration process of three different tea extracts (medicinal Rosil No. 6, Black, and Forest Fruit teas) using the osmotic evaporation (OE) process, was studied. The effect of the OE process on the content of phenolic compounds and antioxidant activity was evaluated. The concentration process was carried out in a hollow-fibre membrane contactor with an effective surface area of 0.54 m2. The tea extract was circulated through the shell side of the contactor, while a concentrated osmotic solution (CaCl2 5 M) was circulated inside the fibres. The flux, the driving force, and the mass transfer coefficient were evaluated. A decrease of the water flux over time was observed and was attributed only to the decrease of the driving force, caused by the dilution of the osmotic solution. Using a surface area/feed volume ratio of 774 m2 m3, it is possible to reach a tea concentration of 40% (w/w) in 5 h, with a constant water flux and without losing the phenolic content and antioxidant potential in most teasinfo:eu-repo/semantics/publishedVersio

A novel cellulose-based polymer for efficient removal of methylene blue

UID/QUI/50006/2019A novel cellulose-based cross-linked polymer, dicarboxymethyl cellulose (DCMC), has been synthesized and used for methylene blue (MB) removal. Inductively coupled plasma atomic emission spectrometry (ICP-AES), Fourier-transform infrared spectroscopy (FTIR), nitrogen porosimetry, and optical microscopy were employed to characterize the structure of the cellulose-based adsorbent. The number of carboxylate groups per gram of polymer (CG) was calculated with sodium content determined by ICP-AES. Systematic equilibrium and kinetic adsorption studies were performed to assess the polymer suitability for dye removal. The effect of pH on its adsorption capacity was also studied and the equilibrium adsorption data was analyzed using Langmuir, Freundlich, and Sips isotherms. At pH = 3, the adsorption isotherms followed the Langmuir model with a maximum adsorption capacity of 887.6 mg/g. At pH = 6.4, the adsorption isotherms produced S-shape curves and were best fitted with the Sips model. The maximum MB uptake increased to 1354.6 mg/g. Pseudo first-order and second-order models were used to fit the kinetic data. A pseudo second-order kinetic model provided the best correlation for the adsorption of MB onto DCMC. Adsorption coupled with membrane filtration achieved 95% methylene blue removal and DCMC can be successfully regenerated and reused in consecutive experiments.publishersversionpublishe

Carbon dioxide separation from anaesthetic gases with membrane contactors and biocompatible ionic liquids

This work aims the development of a self-renewable technology for CO2 separation from anaesthetic gas streams using hollow fiber membrane contactors with biocompatible ionic liquids and carbonic anhydrase (CA) enzyme. Aiming this objective, a system with two hollow-fiber membrane modules is considered, one for the removal of CO2 and the other for the regeneration of the ionic liquid and enzyme. Figure 1 illustrates the proposed concept of this work for an anaesthetic gas closed-circuit. Please click Additional Files below to see the full abstract

Decolorization of a corn fiber arabinoxylan extract and formulation of biodegradable films for food packaging

UID/AGR/04129/2020Corn fiber from the corn starch industry is a by-product produced in large quantity that is mainly used in animal feed formulations, though it is still rich in valuable components, such as arabinoxylans, with proven film-forming ability. During arabinoxylans’ recovery under alkaline extraction, a dark-colored biopolymer fraction is obtained. In this work, a purified arabinoxylan extract from corn fiber with an intense brownish color was decolorized using hydrogen peroxide as the decolorizing agent. Biodegradable films prepared by casting the decolorized extract exhibited a light-yellow color, considered more appealing, envisaging their application in food packaging. Films were prepared with glycerol as plasticizer and citric acid as cross-linker. Although the cross-linking reaction was not effective, films presented antioxidant activity, a water vapor permeability similar to that of non-decolorized films, and other polysaccharides’ and mechanical properties that enable their application as packaging materials of low-water-content food products.publishersversionpublishe

Recovery and Purification of Cutin from Tomato By-Products for Application in Hydrophobic Films

UID/AGR/04129/2020. Sociedade Ponto Verde—Sociedade Gestora de Resíduos de Embalagens, S.A., through the project entitled “Bioplastics and Edible, Vegan Films”. Publisher Copyright: © 2023 by the authors.Tomato pomace is a low-cost, renewable resource that has been studied for the extraction of the biopolyester cutin, which is mainly composed of long-chain hydroxy fatty acids. These are excellent building blocks to produce new hydrophobic biopolymers. In this work, the monomers of cutin were extracted and isolated from tomato pomace and utilized to produce cutin-based films. Several strategies for the depolymerization and isolation of monomeric cutin were explored. Strategies differed in the state of the raw material at the beginning of the extraction process, the existence of a tomato peel dewaxing step, the type of solvent used, the type of alkaline hydrolysis, and the isolation method of cutin monomers. These strategies enabled the production of extracts enriched in fatty acids (16-hydroxyhexadecanoic, hexadecanedioic, stearic, and linoleic, among others). Cutin and chitosan-based films were successfully cast from cutin extracts and commercial chitosan. Films were characterized regarding their thickness (0.103 ± 0.004 mm and 0.106 ± 0.005 mm), color, surface morphology, water contact angle (93.37 ± 0.31° and 95.15 ± 0.53°), and water vapor permeability ((3.84 ± 0.39) × 10−11 mol·m/m2·s·Pa and (4.91 ± 1.33) × 10−11 mol·m/m2·s·Pa). Cutin and chitosan-based films showed great potential to be used in food packaging and provide an application for tomato processing waste.publishersversionpublishe

Membrane Integration in Biomedical Microdevices

El objetivo principal de esta tesis es el desarrollo y fabricación de un dispositivo microfluídico basado en membranas integradas y el estudio de diversos “contactores de membrana” para las diversas aplicaciones biomedicas. Los dispositivos microfluídicos se fabricaron y se aplicarón en la oxigenación de la sangre y separación de la mezcla de gas anestésico. Para la oxigenación de la sangre, el modelo matemático de transferencia de oxígeno en las unidades principales de los dispositivos microfluídicos subraya la importancia de la arquitectura de bifurcación y la distribución de los distribuidores del flujo dentro de la cámara de líquido.La aplicación de un microcontactor de membrana líquida gaseosa para la eliminación en línea de CO2 demostró cuán efectivos pueden ser los dispositivos miniaturizados para los estudios fundamentales de recuperación de gas anestésico.<br /

Bio‐based sensors for smart food packaging—current applications and future trends

Intelligent food packaging is emerging as a novel technology, capable of monitoring the quality and safety of food during its shelf‐life time. This technology makes use of indicators and sensors that are applied in the packaging and that detect changes in physiological variations of the foodstuffs (due to microbial and chemical degradation). These indicators usually provide information, e.g., on the degree of freshness of the product packed, through a color change, which is easily identified, either by the food distributor and the consumer. However, most of the indicators that are currently used are non‐renewable and non‐biodegradable synthetic materials. Because there is an imperative need to improve food packaging sustainability, choice of sensors should also reflect this requirement. Therefore, this work aims to revise the latest information on bio‐based sensors, based on compounds obtained from natural extracts, that can, in association with biopolymers, act as intelligent or smart food packaging. Its application into several perishable foods is summarized. It is clear that bioactive extracts, e.g., anthocyanins, obtained from a variety of sources, including by‐products of the food industry, present a substantial potential to act as bio‐sensors. Yet, there are still some limitations that need to be surpassed before this technology reaches a mature commercial stage.publishersversionpublishe

Purification of Arabinoxylans from corn fiber and preparation of bioactive films for food packaging

Corn fiber, a by-product of the starch industry, is presently incorporated in animal feed. However, it has arabinoxylans as added-value components (besides ferulic acid) that should be valorized. In this work, the raw material, a fraction enriched in arabinoxylans from corn fiber, previously produced by alkaline extraction from corn fiber and pre-concentrated by ultrafiltration, was further purified. The use of ultrafiltration operated in diafiltration mode (dia-ultrafiltration) was evaluated for the purification of the arabinoxylans fraction. The objective was to maximize the removal of the small contaminants from the fraction and to maximize the permeability and/or the permeate flux, by selecting the relevant operating conditions involved in this process. The removal of contaminants (%) was estimated when their apparent rejection stabilized. Edible films were produced, from the resultant purified arabinoxylans fraction, using glycerol as plasticizer (30% dry basis). Additionally, films with the incorporation of ferulic acid were developed, in order to obtain barriers with antioxidant activity. The films were characterized in terms of mechanical properties, antioxidant activity and permeability to water vapor. The films prepared presented a good potential to be used as packaging for food products with low water contentinfo:eu-repo/semantics/publishedVersio

Monitoring of membrane processes with fluorescence molecular probes

This work discusses the use of molecular probes that change their fluorescence response in the presence of different local environmental conditions. In particular, probes able to respond to temperature and to oxygen concentration were identified and used to report the value of these parameters at a molecular scale. The development of a stable, reproducible and sensitive molecular probing system was then applied to monitor oxygen concentration at the surface of different membrane materials and also in order to obtain oxygen concentration profiles inside dense membranes. Ultimately, a temperature sensitive probe was used to measure temperature at membrane surfaces making possible its measurement locally. This technique was applied with success to experimentally measure temperature polarization in membrane distillation processes, on-line, in a non-invasive mode. Future developments of molecular probing will be also presented and discussed