Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations. / <p>Akademisk avhandling som för avläggande av teknologie doktorsexamen vid Chalmers tekniska högskola försvaras vid offentlig disputation den 4 april 2014, klockan 9:30 i KE-salen, Kemigården 4, Göteborg.</p>

Biofuels production and utilisation can reduce the emission of greenhouse gases, dependence on fossil fuels and also improve energy security. Ethanol is the most important biofuel in the transportation sector; however, its production from lignocelluloses faces some challenges. Conventionally, lignocellulosic hydrolysis and fermentation has mostly been performed by separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). SHF results in product inhibition during enzymatic hydrolysis and increased contamination risk. During SSF, suboptimal conditions are used and the fermenting organism cannot be reused. Bacterial contamination is another major concern in ethanol production, which usually results in low ethanol yield. In these studies, the above-mentioned challenges have been addressed. A novel method for lignocellulosic ethanol production ‘Simultaneous saccharification filtration and fermentation (SSFF)’ was developed. It circumvents the disadvantages of SSF and SHF; specifically, it uses a membrane for filtration and allows both the hydrolysis and fermentation to be carried out at different optimum conditions. SSFF also offers the possibility of cell reuse for several cultivations. The method was initially applied to pretreated spruce, with a flocculating strain of yeast Saccharomyces cerevisiae. SSFF was further developed and applied to pretreated wheat straw, a xylose rich lignocellulosic material, using encapsulated xylose fermenting strain of S. cerevisiae. High solids loading of 12% suspended solids (SS) was used to combat bacterial contamination and improve ethanol yield. Oil palm empty fruit bunch (OPEFB) was pretreated with fungal and phosphoric acid in order to improve its ethanol yield. An evaluation of biofuel production in Nigeria was also carried out. SSFF resulted in ethanol yield of 85% of the theoretical yield from pretreated spruce with the flocculating strain. Combination of SSFF with encapsulated xylose fermenting strain facilitated simultaneous glucose and xylose utilisation when applied to pretreated wheat straw; this resulted in complete glucose consumption and 80% xylose utilisation and consequently, 90% ethanol yield of the theoretical level. High solids loading of 12% SS of pretreated birch resulted in 47.2 g/L ethanol concentration and kept bacterial infection under control; only 2.9 g/L of lactic acid was produced at the end of fermentation, which lasted for 160 h while high lactic acid concentrations of 42.6 g/L and 35.5 g/L were produced from 10% SS and 8% SS, respectively. Phosphoric acid pretreatment as well as combination of fungal and phosphoric pretreatment improved the ethanol yield of raw OPEFB from 15% to 89% and 63% of the theoretical value, respectively. In conclusion, these studies show that SSFF can potentially replace the conventional methods of lignocellulosic ethanol production and that high solids loading can be used to suppress bacterial infections during ethanol productions, as well as that phosphoric acid pretreatment can improve ethanol yield from lignocellulosic biomass. / <p>Thesis for the degree of Doctor of Philosophy at the University of Borås to be publicly defended on 31 October 2014, 10.00 a. m. in room E310, University of Borås, Allégatan 1, Borås.</p>

Microalgae are a diverse group of unicellular microorganisms found in various environments, ranging from small garden ponds to lakes with extreme salinity. Common for all microalgae is their ability to convert solar energy and carbon dioxide into chemical energy via photosynthesis. Additionally, they are capable of assimilating large amounts of nitrogen and phosphorus to produce proteins and lipids. These abilities have made microalgae an interesting candidate for next generation wastewater treatment coupled with production of biogas, a renewable energy source in advancement. At the Nykvarn wastewater treatment plant in Linköping, Sweden, 15,400,000 m3 of wastewater are treated annually to remove nitrogen and phosphorus that otherwise would risk to cause eutrophication in surrounding lakes and rivers. Moreover, the treatment plant manages large amounts of sewage sludge that is anaerobically digested to produce biogas and simultaneously reduce the sludge volumes. At the Nykvarn wastewater treatment plant, dewatering of the digested sludge results in a sludge fraction of about 30 % dry content and reject water, which is very nutrient-rich and therefore requires treatment in a SHARON process before it is reintroduced to the main stream of the wastewater treatment plant. In this thesis, the potential of microalgae for nutrient assimilation was studied by monitoring the nutrient removal efficiency of a mixed culture of microalgae when fed with 1) 100 % incoming wastewater, 2) 80 % incoming wastewater + 20 % reject water and 3) 60 % incoming wastewater + 40 % reject water. Furthermore, the effect of a process additive on the nutrient removal efficiency was evaluated. The results showed that microalgae are capable of removing 100 % of ingoing ammonium nitrogen and phosphate phosphorus when fed with incoming wastewater. At transition to 20 % and 40 % reject water, the culture was light-limited with a resulting ammonium reduction of 60 % and a phosphate reduction of around 30 %. The process additive slightly improved the ammonium reduction, however, mainly by formation of nitrite and nitrate by nitrifying bacteria. Moreover, a bio-methane potential test compared the methane potential of the microalgal biomass and the biomass from the SHARON process. The test resulted in an accumulated methane production around 70 mL g-1 VS-1 for the microalgal biomass and 35 mL g-1 VS-1 for the biomass from the SHARON process. That is, the mixed microalgal culture used in this experiment has a methane potential twice that of the biomass from the SHARON process. Finally, an economic analysis of a microalgae based process for purification of reject water showed that the operating costs exceed those of the SHARON process due to high energy consumption. It is thus necessary to choose a cultivation system that effectively utilize the solar energy, as well as maximize the biogas yield from anaerobic digestion of microalgal biomass.

This study is dedicated to investigation of soot formed during combustion in diesel engine. Measurements were performed in a high speed direct injection optical diesel engine. Initially soot particle size, size distribution and soot volume fraction were investigated using time resolved laser induced incandescence (TR-LII) technique. For this study standard diesel fuel was used and measurements were performed for various injection timing and two different engine loads. Investigation showed that TR-LII is a powerful tool that can be used for characterization of in-cylinder soot in the engines. Subsequently TR-LII technique was developed to measure in-cylinder soot in two dimensional plane (planar laser induced incandescence PLII) and technique was combined with high speed imaging to investigate soot processes for ultra-low sulfur diesel (ULSD) and bio-fuel (RME). Two injection strategies of single and double injection were applied during these measurements. A high speed imaging technique was used to study the soot formation and oxidation during the combustion process within the cylinder and PLII was applied later in the stroke to study qualitatively the relative amount of un-oxidised soot that was left in the combustion chamber. In addition to PLII, TR-LII technique was used simultaneously to explore crank angle resolved variation of primary soot particle size and their size distribution during the expansion stroke. The same measurements were repeated for fuels with different composition investigating the relationship between the fuel properties and soot emission. Finally mathematical model for soot particle size and distribution width was modified by introducing assumption of multi-lognormal in-cylinder soot particle size distribution.

Cellulolytic organisms are being heavily studied for the production of biofuels, given that lignocellulosic biomass would be a cheap, abundant, and renewable starting material for chemical production. A challenge with cellulolytic microorganisms is that they are typically poorly characterized and often difficult to genetically manipulate. Our group focuses characterization and engineering of a thermophilic aerobic, cellulolytic actinobacterium, Thermobifida fusca. The wider range of optimal temperature and pH for the growth condition, besides the secretion of several group of cellulases, have made this microbe a potentially efficient host system for industrially application. After the development of first ever successful genetic manipulation protocol by for T. fusca in 2011 in our group the quest continues to better understand and further explore this microbe with such remarkable capabilities. Available genome annotation of the bacteria gives a preliminary clue towards the exploration of its biological system. Genome-scale metabolic reconstruction provides one such framework to populate all the available piece of information to mimic the biological systems to the closest functional state. Further, this skeletal base network can be made more realistic by applying the constraint that controls the flux through various reactions in the pathway network thereby providing the optimal solution space for operation. For the purpose of curation of this in silico model, we aim to integrate the experimental datasets (proteomic and metabolomics) and optimize the agreement between the in silico and in vivo conditions at a steady state condition. Once the model considerably imitates the original biological network, it will be used for the fundamental understanding of the microbial system for the application towards production biofuel and high yields of compound of pharmaceutical interest. The ultimate objective of this project is to design the candidate strain for the cellulolytic production of Natural products. Natural products play an important role in manufacturing of several active pharmaceutical ingredients (APIs). APIs or precursors of APIs can be produced in living organisms with the major challenge of designing and optimizing metabolic pathways to obtain the compounds of interest. In this capacity, living organisms can act as renewable catalysts with high product specificity to produce APIs with potential cost savings over purely synthetic chemistry synthesis routes. This is an effort to understand and design industrially usable microorganism T. fusca to act as a host system for the purpose of production of these compounds. The present project focuses on, in silico characterization and experimental validation of T. fusca, with particular focus on the terpenoids backbone biosynthesis (TBB) pathways using a genome-scale metabolic model, transcriptomics, proteomics and metabolite analysis. The DXP pathway leads to the production of terpenoids precursors that have applications in nutraceutics and pharmaceutics. This study generates the metabolic model, iTFU975 for T. fusca based on the proteomics dataset as the starting point. Further the model and the experimental dataset together helps to characterize the secondary metabolites pathways and compounds in the network associated with the production of terpenoids. In conclusion, this is an effort to characterize the natural products biosynthesis in T. fusca by establishing a bridge between the analytical methodologies and computational efficiencies on “-omics” knowledge to prove the diverse applicability of Systems Biology.

Le début de ce siècle a été marqué par un regain d’intérêt pour le développement des biocarburants. L’engagement de la communauté internationale pour la réduction des émissions de gaz à effet de serre, les préoccupations énergétiques et les débouchés agricoles, ont été les principales raisons qui ont motivé ce développement. Dès lors, la production et la consommation de biocarburants ont considérablement augmenté et ont pris une dimension internationale. L’ampleur du phénomène a suscité des préoccupations d’ordres économique, agricole et environnemental. L’objet de la thèse est d’étudier l’ensemble des implications liées au développement des biocarburants – c’est-à-dire économiques, agricoles et environnementales ¬– et de les inscrire dans le contexte économique mondial.Afin de favoriser les biocarburants face à leurs équivalents fossiles, d’importantes mesures de soutien à l’ensemble des filières des biocarburants ont été instaurées dans les différentes régions du monde. Afin d’étudier la portée de ces politiques, nous avons fait une étude comparative entre les mesures des principaux acteurs (Brésil, Union européenne et Etats-Unis) et des nouveaux acteurs des marchés internationaux. Outre la comparaison des performances économiques et environnementales, nous avons analysé l’influence des politiques de soutien des principaux acteurs sur l’orientation des politiques des nouveaux acteurs engagés dans la production des biocarburants (ou de matières premières).Le second axe de la thèse porte sur les implications agricoles du développement des biocarburants. En effet, de nombreux évènements ont marqué les marchés agricoles mondiaux ces vingt dernières années : le changement d’habitudes alimentaires des pays en développement, la rareté des terres agricoles dans les régions historiquement productrices et exportatrices, les catastrophes naturelles, …, constituent un défi pour les besoins alimentaires futurs. Dans ce contexte, l’avènement des biocarburants représente incontestablement un facteur additionnel aux tensions déjà existantes sur les marchés agricoles mondiaux. En plus d’accroitre la tension sur les prix, le développement des biocarburants participe à la réorganisation de l’architecture de l’agriculture mondiale en faveur des pays en développement.Le dernier axe porte sur les impacts environnementaux des biocarburants. L’internationalisation (de manière directe et/ou indirecte) de la production des biocarburants donnent une nouvelle dimension aux implications environnementales des biocarburants. Notre approche consiste à étudier les impacts environnementaux des biocarburants en séparant les étapes de production de matières premières, de celles de transformation et de consommation. Les résultats montrent que les pays en développement s’exposent à des risques environnementaux élevés. Afin d’éviter ces risques, le développement des biocarburants doit se soumettre à certaines conditions qui permettront d’atteindre une viabilité socio-économique et environnementale. / The beginning of this century was marked by a renewed interest in the development of biofuels. The commitment of the international community to reduce greenhouse gas emissions, energy concerns and agricultural markets were the main reasons for this development. Therefore, the production and consumption of biofuels have increased dramatically and took on an international dimension. This phenomenon magnitude has caused agricultural, environmental and economical concerns. The purpose of the thesis is to study all the implications of the development of biofuels - that is to say, economical, agricultural and environmental - in the context of the global economy. To promote biofuels as opposite to their fossil equivalents, important measures to support all sectors of biofuels have been established in different parts of the world. To study the impact of these policies, we conducted a comparative study between the measurements of the main players (Brazil, European Union and United States) and new actors in international markets. In addition to comparing the economic and environmental performance, we analyzed the influence of political support of key players on the political orientation of new actors involved in the production of biofuels (or raw materials). The second axis of the thesis focuses on the agricultural implications of biofuel development. Indeed, many events have marked the global agricultural markets over the past twenty years: the change in eating habits in developing countries, the scarcity of farmland in the historically producing and exporting regions, natural disasters... is a challenge for future food needs. In this context, the advent of biofuels is certainly an additional factor to existing tensions in global agricultural markets. In addition to increasing the pressure on prices, the development of biofuels contributes to the reorganization of the architecture of global agriculture in favor of developing countries. The last axis addresses the environmental impacts of biofuels. Internationalization (direct and / or indirect) of biofuels production gives a new dimension to the environmental implications of biofuels. Our approach is to study the environmental impacts of biofuels by separating the stages of production of raw materials, those of processing and of consumption. The results show that developing countries are exposed to high environmental risks. To mitigate these risks, the development of biofuels should be subject to certain conditions that will achieve a socio-economical and environmental sustainability.

Doctor of Philosophy / Department of Agricultural Economics / Jason S. Bergtold / The adoption of new technologies on-farm is affected by socio-economic, risk management behavior, and market factors. The adoption of cellulosic biofuel feedstock enterprises and conservation practices plays an important role in the future of Kansas agriculture. No set markets currently exist for bioenergy feedstocks and farmers may be reluctant to produce the feedstocks without contracts to mitigate uncertainty and risk. Adoption of conservation practices to improve soil productivity and health may be affected by risk considerations also. The purpose of this dissertation is to study how market mechanisms and risk influence Kansas farmers’ willingness to adopt cellulosic biofuel feedstock enterprises and conservation practices on-farm. The first essay examines farmers’ willingness to grow switchgrass under contract using a stated choice approach. Data were collected using an enumerated survey of Kansas farmers and analyzed using latent class logistic regression models. Farmers whose primary enterprise is livestock are less inclined to grow switchgrass. In addition, shorter contracts, greater harvest flexibility, crop insurance, and cost-share assistance increase the likelihood farmers will grow switchgrass. The second essay examines how farmers’ risk perceptions impact conservation practice adoption. Factor analysis of survey data was used to identify primary risk management behaviors of Kansas farmers. A multinomial logit model of conservation practice adoption incorporating these risk behaviors was developed. Estimation results indicate that different risk management factors may have no significant impact on practice adoption. Farmers may not consider certain aspects of risk significant in their adoption decision. The third essay examines the effect of different risk management behaviors on farmers’ willingness to produce alternative cellulosic bioenergy feedstocks under contract. Data were collected using a farmer survey with a set of stated choice experiments and analyzed using factor analysis and latent class logistic regression models. While farmers approach risk management differently, the risk management behaviors identified have no significant impact on farmers’ willingness to produce corn stover and switchgrass but have a negative impact on farmers’ willingness to produce sweet sorghum as a biofuel feedstock. These results may indicate that farmers are indifferent toward adopting new bioenergy cropping enterprises when traditional crop production is profitable and more certain.

Doctor of Philosophy / Department of Agronomy / Charles W. Rice / Biofuel feedstocks such as grains and cellulose are gaining increased attention as part of the U.S. portfolio of solutions to address climate change and improve energy security. As the future of biofuels unfolds, major concerns are emerging, including the sustainability of the soil resource in bioenergy cropping system. With a clear understanding of the sustainability risks that exist within the agricultural soil resources, it is now essential to develop metrics that document the soil health as well as the total biomass production of different cropping system. We tested the effectiveness of eight bioenergy plant species grouped between annual and perennial crops. Our main objective was to determine the sustainability of bioenergy cropping systems. There was significantly greater soil structural stability plus greater root biomass under the perennial crops but greater aboveground biomass in the annual crop. Differences in soil carbon measured to 1.2 m were not significant between energy crops after five years. A transparent, unbiased method to identify possible change in soil characteristics under bioenergy cropping practice was offered. Our next metrics were soil aggregate stability and microbial community structure as indicators of soil ecosystem health and environmental stability. The effects 24 years of differing levels of residue and fertilizer inputs on soil aggregate stability, aggregate C and microbial community structure were evaluated. A native, undisturbed prairie site, located nearby was used as a reference in this study. The results showed that greater inputs of inorganic N and increased returns of crop residues did not cause a proportionately greater increase in SOC. The abundance of microbial parameters generally followed their potential carbon pool in cultivated soils but a strong mismatch was observed in the native prairie site. Our results showed for the first time a clear disconnect between decomposers and macroaggregates; highlighting the role of soil structure in protecting organic matter. Soil carbon sequestration is one of the mechanisms that have been proposed as temporary measure to mitigate global climate change. However, there was a particularly large risk of negative effects of mitigation measures related to the increased removal of crop residues from cropping systems for use in bioenergy, if this means that soil carbon is reduced. Effective measurement of soil C at the field scale requires an understanding of the spatial variability of soil C on a landscape scale. Recent technological advances in soil C measurement offer new opportunities in this area. Our surface measurements of soil C by near infrared spectroscopy (NIRS) provided a quick assessment of soil C and, soil C predicted by NIRS and measured by dry combustion laboratory measurements was correlated with and R-squared of 0.84.

Une stratégie d’ingénierie du métabolisme de C. acetobutylicum a été développée afin de construire une souche capable de produire de l’isopropanol à partir de sucres en C5, en C6 ou de substrats plus complexes. Dans un premier temps, une souche de C. acetobutylicum a été ingénieriée pour la production d’un mélange isopropanol/butanol/éthanol (IBE), ce microorganisme n’étant pas capable de produire naturellement de l’isopropanol. Différents opérons, exprimant une voie synthétique de production d’isopropanol, ont été construits et introduits à partir d’un plasmide dans une souche chez laquelle la voie de synthèse du butyrate a été supprimée (C. acetobutylicum ATCC 824 Δcac15ΔuppΔbuk). La souche la plus performante a été sélectionnée à partir de cultures réalisées en fermenteur, en mode discontinu à pH 5,0 et s’est avérée être celle exprimant la voie de l’isopropanol sous la dépendance du promoteur thl. Une optimisation des paramètres de culture a conduit à la production d’un mélange IBE, à partir de glucose, à une concentration de 21 g.l-1, un rendement de 0,34 g.g-1 et une productivité de 0,8 g.l-1.h-1. La production du mélange IBE à partir de xylose ou de xylane comme unique source de carbone a également été démontrée et permet une production IBE de 10,4 g.l-1 avec un rendement de 0,31 g.g-1 sur xylose et une production IBE de 4,28 g.l-1 avec un rendement de 0,28 g.g-1 sur xylane. Enfin, l’analyse des flux passant par la voie de l’isopropanol a permis d’identifier l’étape limitant la production de ce composé. Cette dernière semble être liée à la concentration en acétate intracellulaire et aux propriétés catalytiques la CoA-transférase, qui possède une faible affinité pour l’acétate. Ainsi, une CoA-transférase synthétique basée sur les caractéristiques de la CoA-transférase AtoAD d’E. coli, qui est décrite comme ayant un Km pour l’acétate plus faible, a été conçue et exprimée dans la souche précédement construite afin de tenter de lever la limitation de la voie de synthèse de l’isopropanol. Dans un deuxième temps, des modifications supplémentaires du métabolisme de C. acetobutylicum ont été effectuée afin de produire de l’isopropanol comme unique produit de fermentation à partir de glucose ou de xylose. Différentes stratégies ont alors été évaluées dans le but de contourner le déséquilibre rédox causé par la délétion des voies parasites consommatrices de carbone. Ainsi, des outils permettant la mesure d’activité hydrogénase, in-vivo et in-vitro, ont été développés pour tester la fonctionnalité de 3 hydrogénases, utilisant la bifurcation d’électrons pour la production d’H2 à partir de NADH et de ferrédoxine. Une deuxième stratégie utilisant les potentialités de la voie des phosphocétolases pour la métabolisation du xylose en acétyl-CoA a été étudiée et des résultats prometteurs ont été obtenus malgré les limitations actuellement rencontrées / First, C. acetobutylicum was metabolically engineered to produce a biofuel consisting of an isopropanol/butanol/ethanol (IBE) mixture. Different synthetic isopropanol operons were constructed and introduced on plasmids in a butyrate minus mutant strain (C. acetobutylicum ATCC 824 Δcac15ΔuppΔbuk) in which the butyrate pathway was deleted. The best strain expressing the isopropanol operon from the thl promoter was selected from batch experiments at pH 5.0. By further optimizing the pH of the culture, an IBE mixture with almost no by-products was produced at a titer of 21 g.l-1, a yield of 0.34 g.g-1 and productivity of 0.8 g.l-1.h-1, values never reached before. IBE production was also shown to be efficient using xylose or xylan as the sole carbon source with 10.4 g.l-1 IBE produce at a yield of 0.31 g.g-1 from xylose and 4.28 g.l-1 IBE produce at a yield of 0.28 g.g-1 from xylan. Furthermore, by performing in vivo and in vitro flux analysis of the synthetic isopropanol pathway, this flux was identified to be limited by acetate intracellular concentration and the high Km of CoA-transferase for acetate. A synthetic CoA-transferase based on the AtoAD E. coli characteristics was designed, synthesized and evaluated in vivo. This enzyme, that displays a lower Km for acetate, was found to be a good candidate to alleviate the bottleneck of the isopropanol pathway. Secondly, several strategies were evaluated to redraw C. acetobutylicum metabolism and finally construct a strain able to produce isopropanol as the only fermentation product from glucose or xylose. To overcome the severe redox imbalance caused by homo-isopropanolic fermentation, several strategies were investigated. On the one hand, a new class of electron bifurcating enzyme, the NADH hydrogenases, that can use NADH and ferredoxin to produce H2, were evaluated in C. acetobutylicum. This strategy opens the alternative to produce isopropanol and H2 from glucose without any carbon lost. On the other hand, the use of an alternative catabolic pathway, the phosphocetolase pathway, for xylose utilization and acetyl-CoA production was evaluated. These results allow the identification of the metabolic bottlenecks to overcome to obtain a C. acetobutylicum strain able to produce only isopropanol from xylose at high yield

Le remplacement des solvants organiques classiques par une nouvelle génération de solvants moins toxiques et moins polluants est un défi majeur pour l'industrie chimique. Les liquides ioniques (LIs) ont été largement identifiés comme substituts intéressants aux solvants traditionnels. Le but de ce travail est d'étudier la solubilité des sucres ou des constituants issus de la biomasse dans les liquides ioniques afin de pallier au manque de données expérimentales sur les équilibres de phases de systèmes {sucres + LIs} ou {biomasse + LIs}. Les données de solubilité ont été corrélées avec succès en utilisant les modèles thermodynamiques NRTL et UNIQUAC. Cette étude démontre que la méthode de l'antisolvant est une bonne technique pour l'extraction des sucres des LIs. Par conséquent, les liquides ioniques peuvent être facilement recyclés pour être réutilisés. Les natures fondamentales des interactions entre les sucres et les liquides ioniques ont été définies en utilisant le calcul ab initio. Les résultats obtenus par simulation sont en accord avec les données expérimentales et indiquent que les liquides ioniques interagissent avec les sucres par liaisons hydrogène. La seconde partie de ce travail met en évidence que le prétraitement du miscanthus avec les liquides ioniques permet d'obtenir une bonne production d'éthanol (jusqu'à 150 g d'éthanol par kg de miscanthus). Les résultats montrent que les liquides ioniques sont des solvants performants dans le domaine de la conversion des matières premières issues de la biomasse en biocarburant. Ainsi, l'application à l'échelle industrielle de ces procédés d'extraction de la cellulose pourrait être d'un grand intérêt / The replacement of conventional organic solvents by a new generation of solvents less toxic, less flammable and less polluting is a major challenge for the chemical industry. Ionic liquids have been widely promoted as interesting substitutes for traditional solvents. The purpose of this work is to study the solubility of carbohydrates or biomass based materials in ionic liquids in order to overcome the lack of experimental data on phase equilibria of {biomass or carbohydrate-ILs} mixtures. Solubility data were successfully correlated using NRTL and UNIQUAC thermodynamic models. It was found that the antisolvent method is a good technique for the extraction of carbohydrates from ILs. Ionic liquids could be then recycled successfully for reuse. The fundamental natures of the interaction between carbohydrates and ionic liquids were investigated using ab initio calculations. The theoretical results are in good agreement with experimental data. It was concluded that ionic liquids mainly interact with carbohydrates via hydrogen bonding formation. This confirms that the process of dissolution and regeneration of cellulose in ionic liquids is accompanied only with a physical change. The preatreatment of miscanthus with ionic liquids resulted in the regeneration of amorphous, porous cellulose almost free of lignin, which is suitable for enzymatic hydrolysis and fermentation processes. A successful ethanol production was obtained with an overall ethanol yield reached up to 150 g ethanol kg-1 miscanthus. This indicates the high performance of ionic liquids in converting biomass feedstocks into biofuel. Indeed, applying the cellulose extraction processes on the industrial scale could be of great interest