http://hdl.handle.net/10362/3395 Wed, 19 Jun 2013 11:51:50 GMT 2013-06-19T11:51:50Z http://run.unl.pt:80/retrieve/57625/tech.jpg http://hdl.handle.net/10362/3395 http://hdl.handle.net/10362/9781 Title: Development and Characterization of bioactive, edible whey protein films and coatings to improve quality and safety of Food products Authors: Ramos, Óscar Leandro da Silva Description: Dissertação para a obtenção de grau de doutor em Ciências da Engenharia e Tecnologia Sat, 01 Oct 2011 00:00:00 GMT http://hdl.handle.net/10362/9781 2011-10-01T00:00:00Z http://hdl.handle.net/10362/8590 Title: Non-clinical isolates bring new findings on enterococcal virulence Authors: Gaspar, Frédéric Bustos Abstract: Enterococci are Gram-positive lactic acid bacteria, widespread in the environment, present in water, soil, plants and animals, including humans. They typically colonize the skin and mucous membranes, namely the gastrointestinal tract. However, enterococci, and most notably Enterococcus faecalis and Enterococcus faecium, have become problematic causative agents of several nosocomial infections, including urinary tract infections, bacteraemia, surgical sight infections, and endocarditis. Besides being opportunistic pathogens, the resilient bacteria of the genus Enterococcus are key factors contributing to the ripening, flavour, and the organoleptic properties of fermented food products. The ubiquitous nature of enterococci derives from a number of features, which can be intrinsic to the genus or specific to some species or even strains. These traits allow probing the environment in order to adapt, enabling a survival and fitness advantage. They are encoded in numerous genes that can be easily transferable due to the high genomic promiscuity of enterococci. These genes have been ascribed a role in virulence as they are relevant to different stages of the bacterial infection process, including adhesion, colonization, invasion, evasion of the immune system and spread through the hostʼs tissues. Enterococcal virulence factors can be either secreted (cytolysin, proteases, hyaluronidase, superoxide), surface associated (enterococcal surface protein, aggregation substance, extracellular polymeric substances, pilin gene clusters, enterococcal microbial surface component recognizing adhesive matrix molecules), or intracellular. At the time this thesis work began, researchers were starting to realize that virulence factors in enterococcal clinical isolates were also present in isolates from other environments, in particular, where enterococci play beneficial roles, namely food. Since dissemination of virulence factors among food isolates was no longer crucial, other issues started to become relevant in the still debated enterococcal virulence.(...) Description: Dissertation presented to obtain the PhD degree in Biology Fri, 01 Jun 2012 00:00:00 GMT http://hdl.handle.net/10362/8590 2012-06-01T00:00:00Z http://hdl.handle.net/10362/8575 Title: Precious transition metals: the importance of Zn2+, Mn2+ and Cu2+ in the human pathogen Enterococcus faecalis Authors: Abrantes, Marta Coelho Abstract: Enterococcus faecalis is a commensal bacterium able to colonize different sites in the human host, such as the gastrointestinal tract, the genito-urinary tract and the oral cavity. It can also be found in numerous other environments, including soil, sand, water, food products and plants. These bacteria show a dual behavior: they can behave quite harmlessly as commensals, but are able to become opportunistic pathogens and cause serious infections, such as urinary tract infections and endocarditis, in hospital settings. The question as to how these bacteria are able to change from commensalism to pathogenicity has directed many recent studies to focus on the environmental host conditions that may trigger this transition as well as on the underlying molecular mechanisms. Metals are very important elements in the host environment, as they are key components of many proteins and are involved in numerous cell processes in both the host and the invading pathogen. The maintenance of metal homeostasis is fundamental to both to ensure that metabolism and cell functions are functioning properly. Variations in this homeostasis must be tightly regulated. In several Gram positive pathogens, metal homeostasis and regulation has been linked to their pathogenicity. The lack of knowledge on this subject in E. faecalis motivated the work presented in this thesis.(...) Description: Dissertation presented to obtain the Ph.D degree in Biology Sun, 01 Jul 2012 00:00:00 GMT http://hdl.handle.net/10362/8575 2012-07-01T00:00:00Z http://hdl.handle.net/10362/8570 Title: Revealing fungal activity in the presence of ionic liquids Authors: Petković, Marija Abstract: Ionic liquids constitute a vast and heterogeneous group of chemicals, generally non-volatile and of high solvent quality. They are already used in industrial processes; future applications depend heavily on conscious design of ionic liquids. Given especially the global demand for sustainable chemicals, understanding environmental risks is a priority, necessitating a multidisciplinary research approach, covering a broad range of disciplines from biology to chemistry. Ascomycota fungi are highly suitable model organisms, especially due to their environmental ubiquity and important role in the biotic decay of pollutants. This thesis reports the first ever use of Ascomycota fungi to investigate ionic liquids ecotoxicity and environmental persistence. Fungal strains of Penicillium and Aspergillus were in general found to be more tolerant to ionic liquids containing imidazolium, pyridinium, pyrrolidinium, cholinium or phosphonium cations, than any other microorganism tested to date (Chapters II, III and IV). The capacity of the strains to tolerate the ionic liquids tested was apparently correlated to their phylogeny. Ionic liquid toxicity was evaluated using common parameters, such as growth inhibition and death. Less frequently evaluated parameters were also analysed, including monitoring of the integrity of the cellular boundaries of fungal conidia by microscopy (Chapter IV) and determining the diffusible fungal metabolome by ESI-MS and LC (Chapter II and V). Overall, these data significantly contribute to current understanding of structure-activity relationships in ionic liquids. For example toxicity is apparently a function of alkyl chain length of both anion and cation (Chapters III and IV, respectively). A critical review of current understanding of toxicity and environmental impact of the principal ionic liquid groups made it clear that the common generalisation of ionic liquids being either “green” or “toxic”(...) Description: Dissertation presented to obtain the Ph.D degree in Biochemistry Thu, 01 Sep 2011 00:00:00 GMT http://hdl.handle.net/10362/8570 2011-09-01T00:00:00Z