Durant leur cycle de vie, les organismes sont exposés à des variations environnementales capables d'induire des changements physiologiques, morphologiques et comportementaux, résultant d’une plasticité phénotypique. La plasticité phénotypique est la capacité d'un génotype à générer un nouveau phénotype suite à un stress. Ici, nous avons étudié la plasticité phénotypique d’un Cnidaire symbiotique et non-calcifiant, l’anémone de mer Anemonia viridis, à de multiples niveaux de complexité structurale, in vivo et in vitro. In vivo, nous avons identifié les mécanismes sous-jacents de la plasticité phénotypique potentiellement induits par les futurs changements climatiques (acidification et réchauffement des océans). Nos résultats montrent des modifications dans l'utilisation du carbone inorganique par A. viridis exposée à une forte pCO2 lors d’un stress chronique in natura ou lors d’un stress court en conditions contrôlées. Nous avons ainsi observé une diminution des activités anhydrase carbonique, une enzyme clé des mécanismes de concentration du carbone chez les Cnidaires. Nous avons aussi démontré que l'augmentation concomittante de la température modifie la réponse observée lors d'une élévation seule de la pCO2. In vitro, nous avons établi une culture de cellules primaires viables issue de tentacules d’A. viridis en régénération. Nous avons déterminé l'origine gastrodermale des cellules cultivées et validé l'utilisation de ce nouvel outil pour l'étude de la réponse au stress au niveau cellulaire. Ce nouvel outil ouvre une multitude de perspectives pour l'étude des réponses cellulaires aux stress exogènes (changement climatique) et endogènes (contraintes dues à la symbiose) / During the course of their life cycle organisms are exposed to natural environment variations capable of inducing physiological, morphological and behaviour changes, thus a phenotypic plasticity. Phenotypic plasticity is the ability of a genotype to generate a new phenotype following exogeneous or endogeneous stress. Here, we investigated the phenotypic plasticity of the non-calcifying symbiotic cnidarian Anemonia viridis at multiple levels of structural complexity, in vivo and in vitro. In vivo, we determined the mechanisms behind the phenotypic plasticity under expected future climate change (i.e. ocean acidification and ocean warming). Our results show physiological changes in the inorganic carbon use of the sea anemone A. viridis exposed to high pCO2 during a long-term stress in natura or a short-term stress in controlled conditions. We then observed an equivalent decrease in carbonic anhydrase activity, a key enzyme of cnidarian carbon concentrating mechanisms. Also, we demonstrated that an increase in seawater temperature modified the response observed during a high pCO2 scenario. In vitro, we established a viable primary cell culture from regenerating tentacles of A. viridis. We determined the gastrodermal tissue origin of the cultivated cells and validated the use of this new tool to the in vitro study of stress response at the cellular level. The set-up of this powerful in vitro tool will open a multitude of perspectives for the study of cellular responses to exogeneous stress (as global change perturbations) and to endogeneous stress (as the symbiosis constraints experienced by symbiotic cnidarians)

Ocean acidification has the potential to profoundly affect marine ecosystems before the end of this century, but there are large uncertainties on its effects on temperate benthic communities. Volcanic CO2 seeps provide an opportunity to examine and improve our understanding of community responses to ocean acidification. In this thesis, two Mediterranean CO2 seeps (Methana in Greece and Vulcano in Italy) were used to investigate the responses of macroalgae and their epifaunal communities to increased CO2. Changes in plant-herbivore interactions at elevated CO2, as well as adaptation potential of dominant macroalgae and responses of macroalgae and epifauna to concurrent exposure to elevated CO2 and copper pollution, were also examined. Firstly, I determined that volcanic seeps off Methana (Greece) are suitable for ocean acidification studies as they do not have confounding gradients in temperature, salinity, total alkalinity, nutrients, hydrogen sulphide, heavy metals or wave exposure. Calcifying macroalgae abundance decreased as CO2 increased both at Methana and at Vulcano, while fucoid algae seemed to benefit from elevated pCO2 levels. Seasonality greatly affected macroalgal responses to increasing CO2, according to the annual cycles of dominant species. Epifaunal communities of dominant fucoid algae changed at elevated pCO2 as well, with calcifying invertebrates decreasing and polychaetes increasing near the seeps. Herbivore control of macroalgal biomass did not greatly change at elevated pCO2 levels, as limpets had a minor role in controlling macroalgal biomass off Vulcano (Italy) and sea urchins were replaced by herbivorous fish near seeps off Methana. The two macroalgal species examined for signs of long-term acclimatisation (Cystoseira corniculata (Turner) Zanardini and Jania rubens (Linnaeus) J.V.Lamouroux) to ocean acidification using reciprocal transplants did not appear to have permanently acclimatised to elevated pCO2 levels, but changed their physiology in four to nine months depending on the local environment. Furthermore, when exposed to a 36-hour copper pulse at elevated pCO2 levels both seaweed species accumulated more copper in their tissues compared to those exposed to copper in reference pCO2 conditions, and this resulted in altered epifaunal assemblages on C. corniculata. These observations suggest that benthic communities will significantly change as CO2 levels increase, and that long-term acclimatisation is not likely to play a significant role; this would have profound consequences for benthic ecosystems and the services they provide.

A series of studies was undertaken at Plastic Lake-1 (PC1) to determine the sources and controls on S cycling in small headwater catchments on the Precambrian Shield in south-central Ontario. Two observations were made about the S cycle in this region: (1) all streams exhibit highly coherent temporal patterns in SO4 concentrations and export, and (2) most catchments exported more SO4 in stream water than is received in bulk deposition during the past 2 decades. Synchronous temporal patterns in annual SO4 concentrations in both upland and wetland-draining streams were related to changes in climate, specifically those factors that determine catchment dryness. The number of days with no stream flow or stream flow below a critical threshold was a good predictor of the average stream SO4 concentration in a particular year. Sulphate chemistry in the PC1 outflow is highly dependent on processes occurring in a conifer <i>Sphagnum</i> swamp located immediately upstream of the chemical sampling station. Hydrologic inputs to the swamp during the summer determine whether S is retained or released from peat on an annual basis. Drying and re-wetting of <i>Sphagnum</i>-derived peat caused a substantial increase in soluble SO4 in laboratory experiments, which was slightly enhanced at higher temperature, but alternating moisture conditions had no immediate effect on <i>Sphagnum</i>. Despite large inter-annual changes in SO4 release, over the long-term (<i>i. e. </i> 20-years) SO4 inputs and exports from the swamp are in approximate balance. In contrast, the upland portion of PC1 (<i>i. e. </i> PC1-08) consistently exports more SO4 than is input in bulk deposition in every year of record. Even when inputs are increased to account for potential underestimates in dry deposition or weathering, the majority of catchments in this region exhibit net export in many years. Two internal sources are suggested to account for negative budgets: desorption and mineralization. Adsorption/desorption reactions respond directly to changes in SO4 input concentration, and lysimeter data indicate the importance of these processes for buffering short-term changes in SO4 concentration in LFH percolate. Desorption may be the primary direct response of upland soil to decreasing SO4 inputs in deposition and may substantially extend the period of net SO4 export in catchments that have large adsorbed SO4 pools such as PC1. However, the adsorbed pool may be sustained by continuous net release from mineralization, and should also be considered in budget calculations. Mineralization was shown to be responsive to drying and re-wetting events and temperature, although results varied among different materials. Sulphate release from mineral soil did not appear to be influenced by changing moisture, temperature or deposition chemistry in laboratory experiments, although adsorption/desorption reactions may have largely masked small changes in SO4 release <i>via</i> mineralization. The magnitude of organic S storage in mineral soil indicates that this pool could be an important source of export over the long-term. While it is unknown why (or if) mineralization is a net source of SO4 to drainage streams, changes in climate and/or deposition could potentially influence SO4 release from organic compounds. Soil moisture and temperature are important controls on microbial processes in soil, and changes in climate that bring about changes in soil moisture or temperature conditions could affect decomposition and mineralization processes. Similarly, historically high inputs of S and N in deposition may have brought about slow shifts in litter quality (<i>i. e. </i> decreased C:N, C:S) which could also potentially influence decomposition and mineralization rates. In order to predict the future response of surface water chemistry to changes in SO4 (and N) deposition, it is important to consider not only the magnitude of S pools in soil, but also the potential for SO4 cycling between pools. Likewise, models that predict changes in stream SO4 by adsorption isotherm data alone will underestimate the importance of desorption unless the potential for continual replenishment of the adsorbed pool through the relatively slower process of mineralization is also considered. In general, predictions of recovery from S deposition can only be made from a complete understanding of S pools, transformations, and the effects of climate, which are superimposed upon the long-term trend in deposition.

Future changes to the pH and temperature of the oceans are predicted to impact the biodiversity of marine ecosystems, particularly those animals that rely on the process of calcification. The marine intertidal gastropod Littorina littorea can be used as a model of intertidal organism for investigating the effects of ocean acidification and high temperature, alone and in combination because its ability to be quickly adapt against environmental stressor. In the first study a single species population of L. littorea was used to test for physiological and biochemical effects underpinning organismal responses to climate change and ocean acidification. Compared with control conditions, snails decreased metabolic rates by 31% in response to elevated pCO2 while by 15% in response to combined pCO2 and temperature. Decreased metabolic rates were associated with metabolic depression, a strategy to match oxygen demand and availability, and an increase in end-product metabolites in the tissue under acidified treatments, indicating an increased reliance on anaerobic metabolism. This study also showed that anthropogenic alteration of CO2 and temperature may also lead to plastic responses, a fundamental mechanism of many marine gastropods to cope environmental variability. At low pH and elevated temperature in isolation or combined showing lower shell growth than individuals kept under control conditions. Percentage change in shell length and thicknesses was also lower under acidified and temperature in isolation or combined than control condition, making shells were more globular and desiccation rates were higher. Further studies to broader latitudinal ranges for six populations of L. littorea showed that shell growth decreased in all six populations under elevated pCO2 compared to control snails particularly those at range edges. Elevated pCO2 also affected to the reduction of shell length and width that causing shell aspect ratio to increase across latitudinal gradients except individuals from Millport, UK. Percentage changes of aperture width and aperture area were also decrease under elevated pCO2 with greater reduction of aperture area were found at populations in the mid-ranges which is assumed this response might be linked to local adaptation of the individual to microclimatic conditions. This study also showed that metabolic rates were negatively affected by high pCO2 and show non-linear trend across latitudinal gradients in compared to individual kept under normal pCO2 conditions. Metabolomic analysis showed that two northern populations of Trondheim and TromsØ were distinct from other populations when exposed to low temperature (15 °C) with elevated pCO2 due to, in part, high concentrations of thymine, uracil, valine and lysine. A similar separation also occurred under medium (25 °C) and high (35 °C) temperature exposure in which one of northern population (Trondheim) was distinct from other populations and had lower concentrations of alanine, betaine and taurine while higher of valine. These results suggest that populations at northern latitudes may apply different ionic transport mechanisms under elevated pCO2 and elevated temperatures and those populations are likely to vary in terms of their physiological responses to this environmental challenge.

Increasing atmospheric CO2 is causing unprecedented changes in seawater chemistry, yet the uncertainty of the ecological response to these projected changes, termed ‘ocean acidification’, remains considerable at present. To predict the effects of these changes, we need to improve our understanding of the responses of marine primary producers since these drive biogeochemical cycles and determine the structure and function of benthic habitats. The majority of experiments on the effects of ocean acidification on photoautrophs to date have mainly focused on oceanic microalgae, leaving benthic assemblages largely overlooked. Carbon dioxide vents are providing a means for examining and predicting the impacts of ocean acidification on marine ecosystems. In this thesis a temperate CO2 volcanic vent gradient was used to investigate the responses of benthic microalgal assemblages (periphyton, epilithic, epipelic, epipsammic and endolithic) and macroalgae (a calcified phaeophyte, crustose coralline algae and turf algae) to increasing pCO2. The photosynthetic standing crop of microphytobenthic assemblages increased significantly with elevations in CO2 indicating that the productivity of shallow water habitats may be promoted over the course of this century. Some benthic diatoms appear to benefit in naturally CO2 enriched environments whilst benthic cyanobacteria in this study appear to be relatively insensitive to the levels of increase predicted for this century. Dramatic shifts in epilithic macroalgae assemblages were observed along the CO2 gradient and a calcified phaeophyte was revealed as an unexpected ecological winner under ocean acidification scenarios. These observations suggest that benthic algal assemblages have the potential to dramatically alter as CO2 levels continue to rise; this would have profound consequences for the structure and function of benthic ecosystems.

Acidification of surface waters has been recognised as the major water quality problem in the UK uplands. The adverse effects of conifer afforestation on streamwater chemistry and ecology are well documented in acid-sensitive catchments and have mainly been attributed to the enhanced deposition of atmospheric pollutants onto conifer canopies (the “scavenging effect”). Currently, international and national policies promote the expansion of native broadleaf woodland in the UK. Pollutant deposition onto broadleaf canopies is considered less than onto the more aerodynamically rough conifers, but there is concern that largescale broadleaf planting could delay the recovery of acidified waters or lead to further acidification in most sensitive areas. However, there has been limited investigation of the influence of broadleaf woodland cover on streamwater chemistry in the UK. To investigate the effect of woodland cover 14 catchments with different (0-78%) percentages of broadleaf woodland cover were identified in representative acidsensitive areas in north-western and central Scotland (Glen Arnisdale and Loch Katrine area) and northern and south-western England (Ullswater area and Devon) using spatial datasets in a GIS. Streamwater was sampled at high flow from the catchment outlets in winter and spring 2005 and 2006 and was analysed for major cations, anions and trace metals using standard methods. The number of samples ranged from two in the Glen Arnisdale catchments to 10 in the Loch Katrine area catchments which were sampled more intensively. Significant positive correlations were found between percentage broadleaf woodland cover and streamwater NO3 (rs = 0.51) and soluble Al (rs = 0.64) concentrations. The greater NO3 leaching to streamwater in the three most forested catchments (> 50%) was probably due to enhanced N deposition onto woodland canopies and nitrification by alder in the Ullswater area forested catchments. Streamwater NO3 concentrations equalled or exceeded non-marine SO4 in the above catchments indicating that NO3 was the principal excess acidifying ion in catchments with greater woodland cover. The woodland effect on streamwater chemistry in the study catchments was masked to some extent by variability in acid deposition climate and soil type composition. Seasalt inputs were found to be a more important control than woodland cover for streamwater chemistry in the maritime Glen Arnisdale catchments. A risk assessment of acid-sensitivity in the study catchments was conducted by calculating streamwater critical load exceedances using the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models and modelled pollutant deposition for 1995-97 and 2002. Critical loads were exceeded by 0.01 to 1.74 keq H ha-1 yr-1 in two catchments which had woodland covers > 50% and in the Devon control catchment. The remaining 11 study catchments were assessed to be not at risk of acidification, probably due to significantly reduced non-marine S deposition from 1986 to 2001, but seasalt inputs to the Glen Arnisdale catchments might cause acidic streamwater episodes. Acid-sensitivity was also assessed using macroinvertebrates sampled in 11 of the study catchments and the results generally agreed with the critical load assessments. More detailed estimates of the enhancement of dry S and N deposition onto birchwoods in the Loch Katrine area catchments using calculated roughness length within FRAME showed that it posed no risk for streamwater acidification in these catchments because of the high rainfall environment. However, in acid-sensitive areas of the UK with lower rainfall and closer to major pollution sources, enhanced pollutant scavenging by broadleaf woodland canopies could pose a greater risk of acidification to freshwaters. The finding that almost all study catchments with woodland covers less than 30% are well protected from acidification suggests that this is a sensible threshold value for use in risk assessments of the effects of broadleaf woodland planting conducted within the Forests and Water Guidelines. The results of a sensitivity analysis of the Guidelines’ methodology, conducted using parameters such as numbers and timing of streamwater sampling, different runoff estimates and critical acid neutralising capacity values, showed that the Guidelines should be able to protect sensitive freshwaters from acidification in areas where broadleaf woodland is expanding.

Atmospheric CO2 emissions are on the rise and are expected to reach 780 parts per million by the year 2100. Research investigating the impacts of increasing CO2 is a relatively new field and the response of phytoplankton communities is largely unknown, especially in coastal and freshwater ecosystems where no CO2 manipulation studies have completed. The present study attempts to encourage uniformity in methods utilized in CO2 perturbation studies and identifies changes in phytoplankton abundance in freshwater (James River) and coastal ocean (Atlantic, Cape Hatteras) sites. A novel bubbling method to manipulate pCO2 was compared with the classic method of acid addition in conjunction with laboratory and in situ experiments. The novel and classic methods were equally effective at manipulating carbonate chemistry to predicted levels. However, the laboratory experiment saw greater variation in both pCO2 levels and chlorophyll-a concentrations throughout the four-day incubation period. The results from the present study encourage use of the novel methodology in combination with in situ experimental setup to assess changes in phytoplankton communities as a result of pCO2 enrichment. This pairing will allow greater replication of small volume incubations without introducing new abiotic conditions such as temperature and light. Additionally this study found no significant treatment effect on phytoplankton communities in either freshwater James River or coastal Atlantic.

Este estudo teve como objetivo otimizar as propriedades reológicas dos iogurtes probióticos suplementados com leite em pó desnatado (SMP), concentrado proteico de soro (WPC) e caseinato de sódio (Na-Cn), usando desenho experimental tipo simplex centroide, para modelagem de misturas. O estudo das interações entre os ingredientes (proteína concentrada de soro, caseinato de sódio e leite em pó) incluiu sete experimentos sendo três com os ingredientes puros, dois correspondentes a misturas binárias e um para a uma mistura ternária. Em paralelo aos sete experimentos delineados, foi realizado ensaio controle com leite não suplementado. Os leites foram fermentados a 42 °C até pH 4,5 empregando-se as culturas Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus e Bifidus lactis. A cinética de acidificação foi determinada bem como as análises físico-químicas, contagem de bactérias viáveis e características reológicas dos iogurtes. Modelos foram ajustados para os resultados (respostas cinética, contagem de bactérias viáveis e parâmetros reológicos) através de três métodos de regressão (linear, quadrático e cúbico especial) e aplicados às misturas. Os resultados deste estudo mostraram que a fortificação da base de leite com proteína concentrada de soro, caseinato de sódio e leite em pó desnatado, para o mesmo nível de teor de proteína, afetou o perfil de acidificação, a contagem de bactérias viáveis e reologia de iogurtes probióticos. Além disso, foi possível estimar o perfil de acidificação e a contagem de bactérias no leite suplementado com proteínas do leite em pó, concentrado proteico de soro e caseinato de sódio por metodologia de superfície de resposta, bem como calcular aproximadamente as propriedades viscoelásticas dos iogurtes probióticos. Pode-se ressaltar que a otimização das propriedades reológicas dos iogurtes probióticos suplementados com proteínas do leite depende da fonte de proteína utilizada. Por fim, a substituição parcial de 55% de leite em pó desnatado por concentrado proteico de soro e caseinato de sódio simultaneamente poderá reforçar as propriedades reológicas dos iogurtes probióticos, considerando a cinética de acidificação e a contagem de bactérias viáveis. Os resultados foram validados ao longo da vida de prateleira dos produtos, confirmando os valores estimados pelos modelos para a cinética de acidificação, a contagem de bactérias viáveis e as propriedades viscoelásticas, além da avaliação sensorial e da análise de microestrutura. / This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skim milk powder, whey protein concentrate and sodium caseinate throughout an experimental design type centroid simplex for mixture modeling. It included seven trials: three with the pure ingredients, three corresponding to the binary mixtures and one to the ternary one. A control experiment was accomplished with non supplemented milk. Milk was fermented at 42°C until pH 4.5 by Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidus animalis subsp. lactis. The kinetics of acidification was followed as well as physicochemical analyses, enumeration of viable bacteria and rheological characterization of the yoghurts. Models were adjusted to the results (kinetic responses, counts of viable bacteria and rheological parameters) through three regression models (linear, quadratic and cubic special) applied to mixtures. The results showed that the addition of milk proteins affected acidification profile and counts, and enhanced rheological properties of probiotic yoghurt. The estimated results were validated during shelf-life and were confirmed by for the kinetics of acidification, bacterial counts of viable and viscoelastic properties in addition to sensory evaluation and analysis of microstructure.

A total descontaminação do sistema de canais radiculares e da massa dentinária é uma constante preocupação clínica. Diante disso, esta pesquisa teve o objetivo de avaliar o nível de descontaminação dentinária alcançada após irrigação com soluções de hipoclorito de sódio em diferentes concentrações valores de pH. Oitenta dentes bovinos unirradiculados foram divididos em 9 grupos experimentais diferentes. As coroas foram seccionadas e despregadas das raízes. Foram obtidos segmentos de 12mm e os canais instrumentados até a lima K120, preenchidos com EDTA 17%, durante 10 minutos. As raízes foram impermeabilizadas externamente com duas camadas de esmalte. Suspensões de Enterococcus faecalis (ATCC 29212) foram padronizadas em espectrofotômetro (3x108 UFC/mL) e depositadas em microtubos com caldo BHI e um espécime. O protocolo de contaminação seguiu a metodologia de MA et al. (2011) com adaptações. Após 5 dias, os espécimes foram fixados em um dispositivo de apoio esterilizado e irrigados durante 5 minutos com as soluções-teste estabilizadas com tampões: (G1) NaOCl 1% - pH5; (G2) NaOCl 1% - pH7; (G3) NaOCl 1% - pH10; (G4) NaOCl 2,5% - pH5; (G5) NaOCl 2,5% - pH 7; (G6) NaOCl 2,5% - pH10; (G7) NaOCl 5% - pH5; (G8) NaOCl 5% - pH7; (G9) NaOCl 5% - pH10, contendo 8 espécimes cada, além dos grupos controles. Após o tratamento com as soluções irrigadoras, metade dos espécimes é avaliada por cultura microbiológica (contagem de unidades formadoras de colônias UFC/mL das raspas de dentina retiradas das paredes dos canais) e a outra metade do mesmo grupo avaliada por microscopia confocal de varredura a laser (MCVL) e corante Live & Dead. Houve diferença estatística entre diversos grupos, analisados pelos testes de Kruskal-Wallis e Dunn. (p<0,05) Concluiu-se que a solução de hipoclorito de sódio acidificada provocou uma redução significante no número de bactérias. Essa redução foi ainda maior quando a concentração da solução era elevada. / The complete decontamination of root canal system and dentinal mass is a constant clinical concern. Therefore, this study aimed to evaluate the level of dentin decontamination achieved after irrigation with sodium hypochlorite solutions at different concentrations and pH values. Eighty single rooted bovine teeth were divided into 9 different groups. The crowns were sectioned and separated from the roots. Then, there was obtained segments of 12mm and the root canals were instrumented until size #120 K-file and filled with 17% EDTA during 10 minutes. The roots were externally sealed with two layers of nail polish. Suspensions of Enteroccus faecalis (ATCC 29212) were standardized using a spectrophotometer (3x108 CFU/mL) and placed in microtubes containing BHI broth and one sample. The protocol of contamination followed the methodology of MA et al. (2011) with some adjustments. After five days, the samples were fixed in a sterilized device and irrigated during 5 minutes with the tested solutions stabilized by buffers substances: (G1) 1% NaOCl - pH5; (G2) 1% NaOCl - pH7; (G3) NaOCl 1% - pH10; (G4) 2.5% NaOCl - pH5, (G5) 2.5% NaOCl - pH 7, (G6) 2.5% NaOCl - pH10; (G7) 5% NaOCl - pH5; (G8 ) NaOCl 5% - pH 7 (G9) 5% NaOCl - pH10, containing 8 specimens each, and the control groups. After the treatment with the irrigating solutions, half of the specimens were evaluated by microbiological cultures (counting colony forming units CFU/mL of dentine chips removed from the wall of root canals) and the other half of the same group were evaluated by confocal laser scanning microscopy (CLSM) with fluorescent Live & Dead stain. There was statistical difference among various groups (p<0.05) by Kruskal-Wallis and Dunns test. It was concluded that the acidified sodium hypochlorite solution resulted in a significant reduction in the number of bacteria.

Este estudo teve como objetivo otimizar as propriedades reológicas dos iogurtes probióticos suplementados com leite em pó desnatado (SMP), concentrado proteico de soro (WPC) e caseinato de sódio (Na-Cn), usando desenho experimental tipo simplex centroide, para modelagem de misturas. O estudo das interações entre os ingredientes (proteína concentrada de soro, caseinato de sódio e leite em pó) incluiu sete experimentos sendo três com os ingredientes puros, dois correspondentes a misturas binárias e um para a uma mistura ternária. Em paralelo aos sete experimentos delineados, foi realizado ensaio controle com leite não suplementado. Os leites foram fermentados a 42 °C até pH 4,5 empregando-se as culturas Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus e Bifidus lactis. A cinética de acidificação foi determinada bem como as análises físico-químicas, contagem de bactérias viáveis e características reológicas dos iogurtes. Modelos foram ajustados para os resultados (respostas cinética, contagem de bactérias viáveis e parâmetros reológicos) através de três métodos de regressão (linear, quadrático e cúbico especial) e aplicados às misturas. Os resultados deste estudo mostraram que a fortificação da base de leite com proteína concentrada de soro, caseinato de sódio e leite em pó desnatado, para o mesmo nível de teor de proteína, afetou o perfil de acidificação, a contagem de bactérias viáveis e reologia de iogurtes probióticos. Além disso, foi possível estimar o perfil de acidificação e a contagem de bactérias no leite suplementado com proteínas do leite em pó, concentrado proteico de soro e caseinato de sódio por metodologia de superfície de resposta, bem como calcular aproximadamente as propriedades viscoelásticas dos iogurtes probióticos. Pode-se ressaltar que a otimização das propriedades reológicas dos iogurtes probióticos suplementados com proteínas do leite depende da fonte de proteína utilizada. Por fim, a substituição parcial de 55% de leite em pó desnatado por concentrado proteico de soro e caseinato de sódio simultaneamente poderá reforçar as propriedades reológicas dos iogurtes probióticos, considerando a cinética de acidificação e a contagem de bactérias viáveis. Os resultados foram validados ao longo da vida de prateleira dos produtos, confirmando os valores estimados pelos modelos para a cinética de acidificação, a contagem de bactérias viáveis e as propriedades viscoelásticas, além da avaliação sensorial e da análise de microestrutura. / This study aimed to optimize the rheological properties of probiotic yoghurts supplemented with skim milk powder, whey protein concentrate and sodium caseinate throughout an experimental design type centroid simplex for mixture modeling. It included seven trials: three with the pure ingredients, three corresponding to the binary mixtures and one to the ternary one. A control experiment was accomplished with non supplemented milk. Milk was fermented at 42°C until pH 4.5 by Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidus animalis subsp. lactis. The kinetics of acidification was followed as well as physicochemical analyses, enumeration of viable bacteria and rheological characterization of the yoghurts. Models were adjusted to the results (kinetic responses, counts of viable bacteria and rheological parameters) through three regression models (linear, quadratic and cubic special) applied to mixtures. The results showed that the addition of milk proteins affected acidification profile and counts, and enhanced rheological properties of probiotic yoghurt. The estimated results were validated during shelf-life and were confirmed by for the kinetics of acidification, bacterial counts of viable and viscoelastic properties in addition to sensory evaluation and analysis of microstructure.