The inhibitory concentration of natural food preservatives may be biased by the determination methods

The demand for natural antimicrobials as food preservatives has increased due to the growing interest of the population for a healthy lifestyle. The application of screening methods to identify the antimicrobial activity of natural compounds is of great importance. The in vitro determination of antimicrobial activity requires determining their minimum inhibitory concentrations to assess microbial susceptibility. This study aimed to evaluate the minimum inhibitory concentrations of three natural antimicrobial compounds-chitosan, ethanolic propolis extract, and nisin-against 37 microorganisms (different pathogens and spoilage microorganisms) by the methods of agar dilution and drop diffusion on agar. Culture media at different pH values were used for both methods to simulate different food products. Most of the microorganisms were inhibited by chitosan (0.5% w/v) and propolis (10 mg/mL), and most of the Gram-positive bacteria by nisin (25 mu g/mL). Different pH values and the in vitro method used influenced the inhibition of each compound. Generally, lower minimum inhibitory concentrations were observed at lower pH values and for the agar dilution method. Furthermore, some microorganisms inhibited by the compounds on the agar dilution method were not inhibited by the same compounds and at the same concentrations on the drop diffusion technique. This study reinforces the need for using defined standard methods for the in vitro determination of minimum inhibitory concentrations. Natural compounds with potential antimicrobial action are a bet on food preservation. The use of standard techniques such as those used for antimicrobials of clinical applications are crucial to compare results obtained in different studies and different matrices.info:eu-repo/semantics/publishedVersio

Differences in antimicrobial activity of natural compounds by drop diffusion or dilution methods on agar

info:eu-repo/semantics/publishedVersio

Natural antimicrobial agents and their potential on the preservation of food

info:eu-repo/semantics/publishedVersio

Risk associated with water contaminated with listeria monocytogenes and used for irrigation of sprouts

Listeria monocytogenes is a foodborne pathogen that has been associated with outbreaks of listeriosis caused by the consumption of contaminated vegetables 1 Once in contact with plant tissue, the bacteria can adhere and persist for a significant period of time Moreover, the quantity of cells can influence their dissemination and survival within plants 2.info:eu-repo/semantics/publishedVersio

Virtual Research Environment for the ROSSIO infrastructure

Intuitive workspaces are crucial to the productivity of any researcher. In the field of Humanities, researchers usually need to deal with different formats of metadata, often coming from different sources. This is a serious drawback since it makes research a lot more demanding and time consuming. Therefore, shielding the user from this layer of complexity by presenting the data in a user-friendly and accessible interface is of great relevance. Moreover, the exchange of information and resources between researchers is an important aspect regarding the evolution of their work, making it ideal to provide them with a system where they can engage in collaborative activities. ROSSIO is an infrastructure that aims to be a meeting point where researchers have free and intuitive access to diverse digital contents in the areas of Social Sciences, Arts, and Humanities. For instance, this can be accomplished through the creation of a Virtual Research Environment (VRE). To that end, the goal of this dissertation is to develop a VRE that overcomes the mentioned challenges. Once the VRE is developed, researchers will have access to a number of functionalities that facilitate their workflow and research activities.Um ambiente de trabalho e intuitivo é crucial para a produtividade de qualquer investigador. Na área de Humanidades, os investigadores costumam lidar com diferentes formatos de metadados,muitas vezes provenientes de diferentes fontes. Isto é um grande inconveniente, uma vez que torna a investigação muito mais exigente e demorada. Por conseguinte, proteger o utilizador desta camada de complexidade, apresentando os dados numa interface intuitiva e acessível, é bastante vantajoso. Para além disso, a troca de informações e recursos entre investigadores é um aspeto importante no que diz respeito à evolução do seu trabalho, fazendo com que seja ideal fornecer-lhes um sistema onde se possam envolver em atividades de colaboração. O ROSSIO é uma infraestrutura que pretende ser um ponto de encontro onde os investigadores têm acesso aberto e intuitivo a diversos conteúdos digitais nas áreas das Ciências Sociais, Artes, e Humanidades, e uma das suas iniciativas é a criação de um Ambiente Virtual de Investigação (AVI). Para o efeito, o objetivo desta dissertação é desenvolver um AVI que supere os desafios mencionados. Uma vez desenvolvido o AVI, os investigadores terão acesso a uma variedade de funcionalidades que facilitam o seu fluxo de trabalho e as suas atividades de investigação

A spider's bit(e): how far are we from becoming spidermen?

I am a biotechnologist who recently earned a Ph.D. degree in molecular biology and genetics. Although I have always worked with bacteria, I believe knowledge is transversal to the life sciences, through every level of complexity with the due scalability, never underestimating the power of learning from the small things. My research has always been focused on finding new alternatives to overcome current health challenges. Every day, I get the chance to observe that fiction and science are more alike than we might think. It is often only a matter of time.info:eu-repo/semantics/acceptedVersio

The impact of the financial crisis on the financial constraints of portuguese small and medium enterprises

Dissertação de mestrado em FinançasWith the Portuguese financial crisis, companies had to struggle to be able to overcome the difficulties. Some were able to manage those difficulties, but others did not have the possibility to maintain their activity and had to close the doors. But how were their financial constraints affected? What was the impact that the crisis had on small and medium enterprises (SMEs)? To answer these questions, this study analyses the impact of the recent financial crisis and the sovereign credit rating downgrade of 2011 on the financial constraints of Portuguese SMEs, in a way to understand the difficulties that they faced (or still face) after the crisis. In this dissertation is used the Erel, Jang and Weisbach (2015) approach since their analysis also focus only private firms. According to their methodology, three hypotheses should be tested based on the cash flow sensitivity of cash, the cash flow sensitivity of investment and cash holdings. If a firm is financially constrained, these factors should increase. In this case, the results obtained are not the expected because the three hypothesis purposed are all rejected, indicating that private firms and, more specifically, SMEs were not financially constrained after the financial crisis and the Portuguese sovereign credit rating downgrade in 2011. However, this may not mean that companies were well, but instead that they were even worse than expected, since they did not have the possibility to save cash to finance future investments, nor to retain the cash obtained from the cash inflows or even were not able to use their cash flows to invest.Com a crise financeira Portuguesa, as empresas tiveram de batalhar para ultrapassar as dificuldades. Algumas foram capazes de lidar com essas dificuldades, mas outras não tiveram a possibilidade de manter a sua atividade e tiveram de fechar as portas. Mas como é que foram afectadas as suas restrições financeiras? Qual o impacto que a crise teve nas pequenas e medias empresas (PMEs)? Para responder a estas questões, este estudo analisa o impacto da recente crise financeira e da descida do rating soberano em 2011 nas restrições financeiras das PMEs Portuguesas, de forma a perceber as dificuldades que estas enfrentaram (ou que ainda enfrentam) depois da crise. Nesta dissertação é utilizada a abordagem de Erel, Jang and Weisbach (2015), uma vez que estes autores também focam o seu estudo em empresas privadas. De acordo com a sua metodologia, três hipóteses devem ser testadas com base na sensibilidade de caixa ao cash flow, sensibilidade do investimento ao cash flow e acumulação de liquidez. Se uma empresa está financeiramente restringida, estes fatores devem aumentar. Neste caso, os resultados obtidos não são os esperados, pois as três hipóteses propostas são todas rejeitadas indicando que as empresas privadas e, mais especificamente, as PMEs não estavam restringidas financeiramente depois da crise financeira e da descida do rating soberano Português em 2011. Contudo, isto pode não significar que as empresas estavam bem, mas sim que elas estavam ainda piores do que se esperava, uma vez que não tinham possibilidade de poupar dinheiro para financiar futuros investimentos, nem para reter dinheiro proveniente dos cash inflows ou nem foram capazes de utilizar os cash flows para investir

Recovery of clostridioides difficile in different enrichment culture media

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Development of a functional orange juice powder by spray drying

The concept of functional food products has acquired a huge dimension with the enormous number of people concerned about consuming foods with health benefits. An innovative non-dairy functional food would be very attractive, not only to these consumers but also to specific niches in the market (e.g. lactose intolerants and vegetarians). The aim of this work was to develop a powdered functional orange juice. For this, cultures with probiotic characteristics were used and the necessary conditions to obtain the dried product by spray drying were defined. Two cultures were selected, a commercial probiotic, Lactobacillus plantarum 299v and an isolate from a food matrix, Pediococcus acidilactici HA-6111-2. Safety and the presence of some functional characteristics of P. acidilactici were investigated and compared with those of the commercial probiotic. None of the bacteria produced any of the virulence factors investigated; they did not exhibit significant resistance to antibiotics and reductions lower than one logarithmic cycle were observed after exposure to simulated gastro-intestinal tract conditions. It was also verified that both bacteria survived during the spray drying process and subsequent storage for 60 days. Powdered orange juice was initially obtained in a Büchi Mini Spray Dryer at constant feed temperature (ºC), flow rates of feed (mL/min), drying air (%) and compressed air (L/h) and varying inlet and outlet air temperatures (ºC) as well as the ratio of total soluble solids (orange juice): drying aid (10DE maltodextrin or gum Arabic). At selected inlet and outlet air temperatures of 120 ºC and 65 ºC, respectively, and ratio of soluble solids: drying aid of 0.5: 2, high drying yields and powders with low water activities (aw) were obtained. No cell inactivation was observed for each culture after incorporated into orange juice and spray dried. Their survival during storage at 4 ºC was higher than at room temperature under uncontrolled aw. Pediococcus acidilactici was more resistant than L. plantarum, especially during storage at 4 ºC, with logarithmic reductions lower than 1 log-unit during a period of at least seven months. To enhance survival of spray dried bacteria during storage, different pre-spray drying conditions were tested: i) different sugars were added to the culture media used (cell growth in the presence of lactose, followed by glucose resulted in the highest survival) and ii) cells were exposed to different sub-lethal stresses (only survival of L. plantarum cells during storage at room temperature was increased). For both cases, powders obtained were stored under different conditions of temperature, light exposure and aw. Generally, survival was enhanced at 4 °C, aw of 0.03 and absence of light. Cell viability during passage through simulated gastro-intestinal tract conditions was also investigated at the end of the storage at 4 ºC; the viability of both cultures was not enhanced by prior exposure to sub-lethal stresses. Survival of cultures in orange fruit powders obtained by spray-, freeze- and convective hot air drying was investigated during drying and subsequent storage. Cell inactivation was only observed during convective hot air drying (about 2 logarithmic cycle reduction). Minimal reductions were observed for P. acidilactici for most conditions of storage while for L. plantarum only during storage at 4 ºC. Taking into account the initial number of cells obtained after each drying process, the techniques which allowed survival of an increased number of cells after storage, were spray- and freeze drying. Better dissolution, color and vitamin C retention were also obtained when these techniques were used. Despite the scale-up and validation at industrial scale being still necessary, spray drying at pilot scale allowed producing a new functional orange juice powder with probiotic characteristics. The bacteria used demonstrated to be good candidates for the development of this product.O conceito de alimento funcional tem adquirido uma enorme dimensão graças ao grande número de pessoas preocupadas em consumir alimentos com benefícios para a saúde. Um alimento funcional inovador, não lácteo, poderá ser de grande interesse não só para este grupo de consumidores, mas também para nichos de mercado específicos (ex. intolerantes à lactose e vegetarianos). Este trabalho teve como objetivo o desenvolvimento de um sumo de laranja funcional desidratado. Foram usadas culturas com características probióticas e definiram-se as condições necessárias para obtenção do produto desidratado através de secagem por atomização. Selecionaram-se duas culturas, um probiótico comercial, Lactobacillus plantarum 299v, e um isolado de uma matriz alimentar, Pediococcus acidilactici HA-6111-2. Testou-se a segurança e a presença de algumas características funcionais de P. acidilactici e comparou-se com o probiótico comercial. Nenhuma das bactérias apresentou quaisquer dos factores de virulência; não exibiram resistências significativas a antibióticos e observou-se uma redução inferior a um ciclo logarítmico após exposição às condições do trato gastro-intestinal simulado. Verificou-se ainda a capacidade de ambas as bactérias sobreviverem ao processo de secagem por atomização e posterior armazenamento durante 60 dias. O sumo de laranja em pó foi obtido, numa primeira fase, por desidratação num Büchi Mini Spray Dryer mantendo constantes a temperatura de alimentação (ºC), as taxas de fluxo de alimentação (ºC), do ar de secagem (%) e do ar comprimido (L/h), variando as temperaturas do ar de entrada e de saída (ºC) e a proporção de sólidos solúveis totais (do sumo): auxiliar de secagem (10DE maltodextrina ou goma arábica). Às temperaturas de entrada e de saída selecionadas de 120 e 65 ºC, respetivamente, e proporção de sólidos solúveis: auxiliar de secagem de 0.5: 2, elevados rendimentos e pós com baixas actividades de água (aw) foram obtidos. Não foi observada inativação celular das culturas após incorporação em sumo de laranja e desidratação por atomização. Observou-se uma sobrevivência superior durante o armazenamento a 4 ºC do que à temperatura ambiente, sob valores de aw não controlados. Pediococcus acidilactici apresentou maior resistência que L. plantarum, especialmente a 4 ºC, com perdas de viabilidade inferiores a um ciclo logarítmico durante um período de, pelo menos, sete meses. Para aumentar a sobrevivência das bactérias desidratadas, diferentes condições pré-secagem foram testadas: i) diferentes açúcares foram adicionados ao meio de cultura (maior sobrevivência após crescimento na presença de lactose e glucose) e ii) exposição das células a diferentes stresses sub-letais (aumento da sobrevivência de L. plantarum durante o armazenamento à temperatura ambiente). Em ambos os casos, os pós obtidos foram armazenados em diferentes condições de temperatura, exposição de luz e aw. Globalmente, a sobrevivência foi superior a 4 ºC, com aw controlada a 0.03 e na ausência de luz. A viabilidade celular das duas culturas durante a passagem pelo trato gastro-intestinal simulado foi também investigada no fim do período de armazenamento a 4 ºC e não aumentou com a exposição aos stresses sub-letais. Avaliou-se a sobrevivência das culturas durante a secagem por diferentes técnicas (atomização, liofilização e convecção por ar quente) e posterior armazenamento nos pós de laranja obtidos. Apenas a secagem por convecção causou inativação celular (redução de 2 ciclos logarítmicos). Reduções mínimas foram observadas para P. acidilactici na maioria das condições de armazenamento, enquanto que para L. plantarum apenas a 4 ºC. Tendo em conta o número inicial de células obtidas após cada processo de secagem, as técnicas que permitiram a sobrevivência de um maior número de células após armazenamento foram as de secagem por atomização e liofilização. Melhor dissolução, cor e retenção de vitamina C foram também obtidas por estas técnicas. Apesar de ser ainda necessário o scale-up e validação à escala industrial, a secagem por atomização à escala piloto permitiu produzir um novo sumo de laranja funcional com características próbioticas. Os microrganismos estudados demonstraram ser bons candidatos para o desenvolvimento desse produto

In vitro antimicrobial activity of various essential oils against clostridioides difficile

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