Dans le contexte de la bioéconomie, la découverte et la caractérisation des enzymes capables de dégrader la paroi végétale est particulièrement intéressante pour l’utilisation de la biomasse lignocellulosique dans l’industrie. A cet égard, la métagénomique fonctionnelle est un outil puissantpour découvrir de nouvelles enzymes à partir d’écosystèmes microbiens variés, comme l’illustrent les travaux sur le tube digestif du termite Pseudacanthotermes militaris. Cette étude a fourni une mine d’informations et identifié un hypothétique locus d’utilisation du xylane (XUS), codant pour cinq glycosides hydrolases (GH) et une carbohydrate esterase (CE) de Bacteroidales.Le XUS du métagénome de Pseudacanthotermes militaris contient une xylanase de la famille GH10 qui possède une organisation modulaire complexe dans laquelle la séquence du domaine GH10 est interrompue par une insertion de deux carbohydrate binding modules (CBM). Des travaux préliminaires ont montré que cette enzyme modulaire, désignée Pm25, est active sur xylane. Par conséquent, un des objectifs de cette étude a été la caractérisation détaillée des propriétés biochimiques et catalytiques de Pm25. Le rôle des CBM a également été examiné en quantifiant les interactions protéines-sucres et permettant ainsi une meilleure compréhension du rôle spécifique de ces modules, les résultats obtenus permettent de cerner l’impact de la modularité de Pm25 sur ses propriétés fonctionnelles.Dans une deuxième partie de l’étude, nous avons entrepris d’étudier la fonction de Pm25 dans le contexte du cluster XUS. Pour ce faire, nous avons étudié les enzymes adjacentes à Pm25 sur le locus,une autre GH10, une GH11, une GH115 et une GH43. La comparaison des paramètres cinétiques et une étude détaillée des produits d’hydrolyse ont été analysés par spectrométrie de masse et ont révélé que la GH10 et la GH11 étaient les enzymes clefs de la dépolymérisation en étant 20 fois plus efficaces que Pm25. En parallèle, nous avons développé un protocole pour l’utilisation de la micro-thermophorèse (MST) pour quantifier les interactions CBM-sucres, une approche intéressante qui nécessite peut d’échantillon et de ligand contrairement à d’autres méthodes biophysiques. Dans l’ensemble, cette étude a révélé le rôle important de Pm25 et ses homologues dans les locus d’utilisation des xylanes chez les Bacteroidetes et a permis d’identifié le sens de cette architecture particulière. / In the context of bioeconomy, the discovery and study of plant-cell wall degrading enzymes is particularly relevant for the use of lignocellulosic biomass for industrial purposes. In this respect, functional metagenomics has proven to be a powerful tool to discover new enzymes from a variety of microbial ecosystems, as exemplified by work performed on the gut of the termite Pseudacanthotermes militaris. This study provided a wealth of information and identified an interesting hypothetical xylan utilization system, encoding five glycoside hydrolases (GH) and one carbohydrate esterase (CE) annotated from bacteroidales. The Pseudacanthotermes militaris-derived putative XUS cluster contains a GH10 xylanase that displays a quite complex modular arrangement wherein the GH10 catalytic module contains two insertional carbohydrate binding modules (CBM). During the preliminary work, this modular enzyme, designated Pm25, was shown to be active on xylan, thus in the present research we set out to more thoroughly characterize its biochemical and catalytic properties.The role of the CBM was also investigated, quantifying protein-carbohydrate interactions and thus providing better insight into the specific role of the modules. Taken together, the results obtained provide insight into how Pm25 modularity translates into functional properties. In second part of our study, we set out investigate the function of Pm25 in the context of the XUS cluster. To achieve this we studied a xylan utilization system, which is constituted by another GH10, GH11, GH115 and GH43. The comparison of kinetic parameters and a detailed end product analysis by mass spectrometry showed that GH10 and GH11 outweigh over 20 fold Pm25 catalytic efficiency. In parallel, we developed the use of MicroScale Thermophoresis (MST) to quantify CBM-carbohydrates interactions, an interesting approach requiring smaller concentration of proteinsand ligands compared to other biophysical methods. Overall this study highlighted the important role of Pm25 homologs in the xylan utilization system in Bacteroidetes, and pinpointed the meaning of its unusual architecture.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / This work was developed with the aim of studying the efficiency of the models that express the relationship of density and diameter in evenaged stands of Pinus taeda L., managed in full density and highly stocked for a bioeconomic model of production. For this, were tested density and diameter models, using data derived from 50 permanent plots, measured annually until 18 age, allocated to settlements established in the spacing of 1.5x1.0 m, 2.5x 1.0 m, 1.5x2.0 m, 2.0x2.0 m, 1.5x3.0 m, 2.5x2.0 m, 2.0x3.0 m and 2.5x3.0 m, kept at full density, in Otacílio Costa, physiographic region of Santa Catarina State plateau.The results of the bioeconomic modeling of production, based on the density management diagram system for tall trees, we concluded that the models proposed by Reineke, Yoda, Zeide and Tang showed a good statistical precision, with a determination coefficient higher than 0,88 and coefficient of variation less than 1.25 % but the model of Tang was more accurate and efficient. The size of the diameter at the point where you start self-thinning in the population varies considerably with the density of trees established per hectare. For all plant spacings analyzed did not prove the value of the slope of -3/2 law of self-thinning proposed by Tang and is a result of the initial spacing. The limit of self-thinning in less dense populations, occurs with a diameter slightly less than in maximum density, which is directly proportional to the density of trees when the implementation of the forest. The model of self-thinning described the management zones of great individuals in the population, between 0.45 and 0.55 limits the maximum density of the forest. The annual increment in diameter between 6 and 7 years, when related to relative density (G/d0,5622) identified five areas of growth, defined by: excessive space - trees grow free of competition;free growth - where growth in diameter is maximum; increased competition- when the diameter increment begins to decrease; full density - when productivity of the stand is maximum; and imminent death - begins when individuals have died by excessive density and high competition. The Diagrams Density Management of the variables mean diameter, basal area, volume by the Population Density Index was efficient and to estimate thisis values with accuracy, showed an efficiency of 0.99. The lines demarcating the areas of competition allow us to project the trajectory of the diameter and density, with the definition of the clearcutting. The Normal, Lnnormal, Weibull and Gamma probability distributions, described accurately the variation of the density of the stands, but the Weibull function with two parameters was comparable to the adjustment by the simplicity and efficiency in the prognosis of frequencies for diameter in time. The shape of the trunk was adjusted by the polynomial of five degree, allowed the best estimates than other models. The net present value of R$ 15587.60 ha-1 was given to the management regime with three thinnings at 9, 13 and 18 years and cut at 22 years, higher than the other schemes simulated. A comparison of management regimes for the equivalence of planning horizons for 28 years, determined by the equivalent annual value, said the management regime with three thinned and cut at 22 years, such as greater economic efficiency, with a value of R$ 1380.10 ha-1. The internal rate of return in any simulated management regimes was highly attractive, with varying from 14.83 % per year in managed regimes stands with three thinning and cut to 22 years to 14.25 % per year in managed regimes stands with threethinning and cut to 18 years. The biggest benefit/costs ratio was 2.81, obtained in the management regime with three thinnings, at 9, 13 and 18 years and final cutting at 22 years. / Este trabalho foi desenvolvido com o objetivo de estudar a eficiência dos modelos que expressam a relação de densidade e diâmetro em povoamentos equiâneos de Pinus taeda L., manejados em densidade completa e altamente estocados, para obtenção de um modelo bioeconômico da produção. Para isso, foram testados modelos de densidadee diâmetro, através de dados originados de 50 parcelas permanentes, medidas anualmente até os 18 anos, alocados em povoamentos implantados em espaçamentos de 1,5x1,0 m, 2,5x1,0 m, 1,5x2,0 m, 2,0x2,0 m, 1,5x3,0 m, 2,5x2,0 m, 2,0x3,0 m e 2,5x3,0 m, mantidos em densidade completa, em Otacílio Costa, região fisiográfica do planalto do estado de Santa Catarina. Os resultados obtidos da modelagem bioeconômica da produção, baseada no Diagrama de Manejo da Densidade para sistema de alto fuste, permitiram concluir que os modelos propostos por Reineke, Yoda, Zeide e Tang apresentaram uma boa precisão estatística, com um coeficiente de determinação superior a 0,88 e um coeficiente de variação inferior a 1,25%, porém o modelo de Tang mostrou-se mais preciso e eficiente. A dimensão do diâmetro médio no ponto em que inicia o autodesbaste na população varia consideravelmente com a densidade de árvores implantadas por hectare. Para todos os espaçamentos de plantio analisados, não se comprovou o valor do coeficiente angular de -3/2 da lei de autodesbaste proposto por Tang, sendo uma decorrência do espaçamento inicial. O limite de autodesbaste de populações menos densas ocorre com um diâmetro médio pouco inferior ao obtido em máxima densidade, sendo este diretamente proporcional à densidade de árvores quando da implantação da floresta. O modelo de autodesbaste descreveu as zonas de manejo ótimo dos indivíduos na população entre limites de 0,45 e 0,55 da densidade máxima da floresta. O incremento corrente anual em diâmetro entre o 6º e o 7º ano, quando relacionado com a densidade relativa (G/d0,5622), permitiu identificar cinco zonas de crescimento, definidas por: espaço excessivo as árvores crescem livre de concorrência; crescimento livre o incremento em diâmetro é máximo; aumento da competição o incremento em diâmetro começa a diminuir; estoque completo a produtividade do povoamento é máxima; e iminente mortalidade começa a haver morte de indivíduos por densidade excessiva e alta concorrência. Os Diagramas de Manejo da Densidade com as variáveis diâmetro médio, área basal e volume por Índice de Densidade do Povoamento foram eficientes e permitiram estimar estes valores com acurácia, para uma eficiência igual a 0,99. As linhas que delimitam as zonas de concorrência permitem projetar a trajetória do diâmetro por densidade populacional, com definição da idade de corte final. As distribuições de probabilidade Normal, Ln-normal, Weibull e Gama descreveram com acurácia a variação da densidade dos povoamentos, masa função de Weibull, com dois parâmetros, foi compatível pela simplicidade ao ajuste e à eficiência na prognose das frequências por diâmetro no tempo. A forma de tronco ajustada pelo polinômio do 5º grau apresentou melhores estimativas que outros modelos. O Valor Presente Líquido de R$ 15.587,60 ha-1 foi determinado para o regime de manejo com três desbastes, aos 9, 13 e 18 anos e corte final aos 22, superior aos demais regimes simulados. A comparação dos regimes de manejo pela equivalência dos horizontes de planejamento em 28 anos, determinado pelo Valor Anual Equivalente, indicou o regime de manejo com três desbastes e corte final aos 22 anos como o de maior eficiência econômica, com um valor de R$ 1.380,10 ha-1. A taxa interna de retorno em qualquer dos regimes de manejo simulados foi altamente atrativa, tendo variado de 14,83 % a.a. em povoamentos manejados com três desbastes e corte final aos 22 anos a 14,25 % a.a. em povoamentos manejadoscom dois desbastes e corte final aos 18 anos. A maior razão benefício sobre os custos foi de 2,81, obtida no regime de manejo com três desbastes, aos 9, 13 e 18 anos e corte final aos 22.