Optimization of lipase production from yeasts strains isolated from olive mil wastewater

Dissertação submetida à Universidade de Lisboa, Faculdade de Ciências para a obtenção do Grau de Mestre em Microbiologia Aplicada.

The Effect of Residence Time on the Tensile Properties of Superelastic and Thermal Activated Ni-Ti Orthodontic Wires

Since the 1980s, different devices based on superelastic alloys have been developed to fulfill orthodontic applications. Particularly in the last decades several researches have been carried out to evaluate the mechanical behavior of Ni-Ti alloys, including their tensile, torsion and fatigue properties. However, studies regarding the dependence of elastic properties on residence time of Ni-Ti wires in the oral cavity are scarce. Such approach is essential since metallic alloys are submitted to mechanical stresses during orthodontic treatment as well as pH and temperature fluctuations. The goal of the present contribution is to provide elastic stress-strain results to guide the orthodontic choice between martensitic thermal activated and austenitic superelastic Ni-Ti alloys. From the point of view of an orthodontist, the selection of appropriate materials and the correct maintenance of the orthodontic apparatus are essential needs during clinical treatment. The present work evaluated the elastic behavior of Ni-Ti alloy wires with diameters varying from 0.014 to 0.020 inches, submitted to hysteresis tensile tests with 8% strain. Tensile tests were performed after periods of use of 1, 2 and 3 months in the oral cavity of patients submitted to orthodontic treatment. The results from the hysteresis tests allowed to exam the strain range covered by isostress lines upon loading and unloading, as well as the residual strain after unloading for both superelastic and thermal activated Ni-Ti wires. Superelastic Ni-Ti wires exhibited higher load isostress values compared to thermal activated wires. It was found that such differences in the load isostress values can increase with increasing residence time.

Microstructure and tensile properties of carbon-epoxy laminates produced by automated fibre placement: Influence of a caul plate on the effects of gap and overlap embedded defects

Automated fibre placement (AFP) enables the trajectory of unidirectional composite tape to be optimized, but laying down complex shapes with this technology can result in the introduction of defects. The aim of this experimental study is to investigate the influence of gaps and overlaps on the microstructure and tensile properties of carbon-epoxy laminates. First, a comparison between a hand-layup and AFP layup, draped and cured under the same conditions, shows equivalent microstructures and tensile properties. This provides the reference values for the study. Then, gap and overlap embedded defects (more or less severe) are introduced during manufacturing, on two cross-ply layups [(0°/(90°)5/0°] and [(90°/0°)2/90°]. Autoclave cure without a caul plate results in local thickness variation and microstructural changes which depend on the defect type. This has a strong influence on mechanical performance. Use of a caul plate avoids these variations and in this case embedded defects hardly affect tensile properties.

Comparative transcriptome profiling of human foreskin fibroblasts infected with the Sylvio and Y strains of Trypanosoma cruzi

Trypanosoma cruzi, the causative agent of Chagas Disease, is phylogenetically distributed into nearly identical genetic strains which show divergent clinical presentations including differences in rates of cardiomyopathy in humans, different vector species and transmission cycles, and differential congenital transmission in a mouse model. The population structure of these strains divides into two groups, which are geographically and clinically distinct. The aim of this study was to compare the transcriptome of two strains of T. cruzi, Sylvio vs. Y to identify differences in expression that could account for clinical and biochemical differences. We collected and sequenced RNA from T. cruzi-infected and control Human Foreskin Fibroblasts at three timepoints. Differential expression analysis identified gene expression profiles at different timepoints in Sylvio infections, and between Sylvio and Y infections in both parasite and host. The Sylvio strain parasite and the host response to Sylvio infection largely mirrored the host-pathogen interaction seen in our previous Y strain work. IL-8 was more highly expressed in Sylvio-infected HFFs than in Y-infected HFFs.

Comparing the expression of human DNA topoisomerase I in KM71H and X33 strains of Pichia pastoris

Background: Human is an essential cellular enzyme that is found in all human cells. As this enzyme is upregulated in cancer cells exceedingly, it is used as a target for cancer chemotherapeutic drug development. As such, producing the in-house enzyme for the purpose to speed up the search for more cost-effective and target specific hTopoI inhibitors is warranted. This study aims to compare the optimised conditions for the expression of hTopoI in KM71H (MutS) and X33 (Mut+) strains of Pichia pastoris P. pastoris transfected with an hTopoI recombinant vector was used for the optimization of a higher level of hTopoI expression. Results: In the process, fed-batch cultivation parameters that influence the expression of hTopoI, such as culture temperature, methanol induction and feeding strategy, were optimised in the transfected KM71H and X33 P. pastoris strains in a shake flask system. The cell density and total protein concentration (protein level) of transfected P. pastoris were compared to determine the optimum culture conditions for each transfected P. pastoris strain. A higher hTopoI level was observed in the transfected KM71H culture supernatant (2.26 ng/mL) when the culture was incubated in the optimum conditions. Conclusions: This study demonstrated that MutS strain (KM71H) expressed and secreted a higher level of hTopoI heterologous protein in the presence of methanol compared to the Mut+ strain; X33 (0.75 ng/mL). However, other aspects of optimization, such as pH, should also be considered in the future, to obtain the optimum expression level of hTopoI in P. pastoris.

Antibiotics resistance of Stenotrophomonas maltophilia strains isolated from various clinical specimens.

Background: A limited number of antibiotics are recommended for the therapy of Stenotrophomonas maltophilia infections due to therapy difficulties caused by its numerous mechanisms of resistance. Objectives: In this study conducted over a period of approximately 5 years we aimed to determine resistance rates of S. maltphilia based on drug classification recommended by Clinical and Laboratory Standards Institute. Methods: A total of 118 S. maltphilia strains isolated from various clinical specimens between January 2006 and June 2012 were included in the study. BD Phoenixautomated microbiology system (Becton Dickinson, USA) was utilized for species level identification and antibiotic susceptibility testing. Results: Sixty seven of S. maltphilia strains were isolated from tracheal aspirate isolates, 17 from blood, 10 from sputum, 10 from wound and 14 from other clinical specimens. Levofloxacin was found to be the most effective antibiotic against S. maltphilia strains with resistance rate of 7.6%. The resistance rates to other antibiotics were as follows: chloramphenicol 18.2%, trimethoprim-sulfamethoxazole 20.3% and ceftazidime 72%. Conclusion: The study revealed that S. maltphilia is resistant to many antibiotics. The treatment of infections caused by S. maltphilia should be preferred primarily as levofloxacin, chloramphenicol, and TMP-SXT, respectively.

Aplicação do método de Elementos Finitos eXtendido (MEFX) para a previsão da resistência de juntas adesivas de sobreposição dupla

As ligações adesivas têm sido utilizadas em diversas áreas de aplicação. A utilização das juntas adesivas em aplicações industriais tem vindo a aumentar nos últimos anos, por causa das vantagens significativas que apresentam comparativamente com os métodos tradicionais de ligação tais como soldadura, ligações aparafusadas e rebitadas. A redução de peso, redução de concentrações de tensões e facilidade de fabrico são algumas das principais vantagens das ligações adesivas. Devido à crescente utilização das ligações adesivas, torna-se necessário a existência de ferramentas que permitam prever a resistência das juntas com elevada precisão. Assim, para a análise de juntas adesivas, está a ser cada vez mais utilizado o método de Elementos Finitos. Neste âmbito o Método de Elementos Finitos eXtendido (MEFX) perfila-se como um método capaz de prever o comportamento da junta, embora este ainda não esteja convenientemente estudado no que diz respeito à aplicação a juntas adesivas. Neste trabalho é apresentado um estudo experimental e numérico pelo MEFX de juntas de sobreposição dupla, nas quais são aplicados adesivos que variam desde frágeis e rígidos, como o caso do Araldite® AV138, até adesivos mais dúcteis, como o Araldite® 2015 e o Sikaforce® 7888. Foram considerados substratos de alumínio (AW6082-T651) em juntas com diferentes comprimentos de sobreposição, sendo sujeitos a esforços de tração de forma a avaliar o seu desempenho. Na análise numérica foi realizada uma análise da distribuição de tensões na camada adesiva, a previsão da resistência das juntas pelo MEFX segundo critérios de iniciação de dano baseados em tensões e deformações, e ainda um estudo sobre o critério energético de propagação de dano. A análise por MEFX revelou que este método é bastante preciso quando usados os critérios de iniciação de dano MAXS e QUADS, e parâmetro com valor de 1 no critério energético de propagação de dano. Apesar de ser um método pouco estudado na literatura comparativamente com outros, o MEFX apresentou resultados muito satisfatórios.

Molecular Profiling of Shiga Toxin-Producing Escherichia coli and Enteropathogenic E. coli Strains Isolated from French Coastal Environments

Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic E. coli (EPEC) strains may be responsible for food-borne infections in humans. Twenty-eight STEC and 75 EPEC strains previously isolated from French shellfish-harvesting areas and their watersheds and belonging to 68 distinguishable serotypes were characterized in this study. High-throughput real-time PCR was used to search for the presence of 75 E. coli virulence-associated gene targets, and genes encoding Shiga toxin (stx) and intimin (eae) were subtyped using PCR tests and DNA sequencing, respectively. The results showed a high level of diversity between strains, with 17 unique virulence gene profiles for STEC and 56 for EPEC. Seven STEC and 15 EPEC strains were found to display a large number or a particular combination of genetic markers of virulence and the presence of stx and/or eae variants, suggesting their potential pathogenicity for humans. Among these, an O26:H11 stx1a eae-β1 strain was associated with a large number of virulence-associated genes (n = 47), including genes carried on the locus of enterocyte effacement (LEE) or other pathogenicity islands, such as OI-122, OI-71, OI-43/48, OI-50, OI-57, and the high-pathogenicity island (HPI). One O91:H21 STEC strain containing 4 stx variants (stx1a, stx2a, stx2c, and stx2d) was found to possess genes associated with pathogenicity islands OI-122, OI-43/48, and OI-15. Among EPEC strains harboring a large number of virulence genes (n, 34 to 50), eight belonged to serotype O26:H11, O103:H2, O103:H25, O145:H28, O157:H7, or O153:H2.

Correlations between thermal environment and egg quality of two layer commercial strains

Heat stress limits the productivity of laying hens, as reflected by egg production and egg quality. The present study aimed at showing the correlations between egg quality parameters and environmental variables recorded on the day eggs were laid and on the previous days. Birds were housed in battery cages in a commercial poultry house. Main component analyses were used to verify associations between environmental and production variables, and Pearson's linear correlation tests were used to further investigate those associations. Analyses were carried out separately for to layer strains, Dekalb® White and Hy-Line® w36, and the variables egg weight (g), eggshell weight (g), specific gravity (g/cm³) and eggshell percentage (%) were compared with the environmental variables of the same day of the production, and one, two, three, and four days before egg production. Sound intensity measured inside the houses was positively associated with the quality parameters of eggs produced on the next day. Thermal environmental variables affected the egg quality differently in each strain, particularly air temperature, internal roof tile temperature, relative humidity, and air velocity. Ammonia concentration measured inside the houses was lower than 1ppm, and did not affect production performance.