Titan, la plus grosse lune de Saturne, est l'un des objets planétaires clé dans le domaine de l'exobiologie. Son atmosphère dense et riche en diazote est le siège d'une chimie organique intense. Ce travail de thèse se concentre sur les aérosols organiques produits dans son atmosphère. Ces derniers jouent un rôle essentiel dans l'évolution de l'atmosphère et de la surface du satellite mais aussi dans sa chimie organique d'intérêt exobiologique. Dans un premier temps, afin de disposer d'analogues de laboratoires (« tholins ») fiables de ces aérosols, un dispositif permettant d'obtenir des tholins propres a été développé, testé puis optimisé. Puis, deux aspects complémentaires des aérosols de Titan ont été étudiés :- Leurs propriétés optiques. En effet, la connaissance de ces dernières est indispensable, entre autres, pour l'analyse et l'interprétation des données d'observations de Titan. Une étude détaillée et critique de l'ensemble des données disponibles relatives aux indices de réfraction a été menée. Elle a permis de mettre en évidence les lacunes à combler. En parallèle, des mesures expérimentale ont permis de déterminer la matrice de diffusion à plusieurs longueurs et pour une large gamme d'angles de diffusion. Les résultats obtenus montrent que les tholins ne présentent pas une forme en agrégats comme les aérosols de Titan bien que les données acquises semblent bien représenter les données d'observations de Titan.- Leurs possibilités d'évolution chimique une fois à la surface, en particulier, la possible interaction des aérosols avec un cryomagma d'eau-ammoniaque. Des modèles de formation de Titan ont permis de déterminer une composition en sel de l'océan interne et de la cryolave. A partir de cette composition originale, une étude expérimentale de diverses hydrolyses des tholins a été effectuée. Les résultats obtenus montrent la formation de nombreux composés organiques dont des molécules d'intérêts exobiologiques, parmi elles, des espèces identifiées seulement en présence de sels. De plus, une liste des précurseurs potentiels de ces composés a été établie ce qui pourrait constituer une base de donnée pour la recherche de la composition chimique des tholins et/ou aérosols de Titan / Titan, the largest moon of Saturn, is one of the key planetary objects in the exobiology field. Its dense, nitrogen-rich atmosphere is the site of intense organic chemistry. This PhD work focuses on the organic aerosols which are produced in Titan's atmosphere. They play an important role in atmospheric and surface processes but also in its organic chemistry of exobiology interest. At first, in order to produce reliable laboratory analogs (“tholins”) of these aerosols, a device for the synthesis of clean tholins has been developed, tested and optimized. Then two complementary aspects of Titan aerosols have been studied :- Their optical properties. Indeed, their knowledge is prime importance to analyze and to better interpret many of Titan's observational data. A detailed and critical review of all available data on refractive indices was conducted. The lacks in this field have been highlighted. In parallel, direct experimental measurements were used to determine the scattering matrix at two wavelengths and for a wide range of scattering angles. The obtained results show that the tholins do not have the shape of aggregates such as Titan aerosols although the acquired data seem to match with observational data.- Their potential chemical evolution at Titan surface, in particular, the possible interaction between aerosols and putative ammonia-water cryomagma. Modelings of Titan formation have recently permitted the characterization of a composition in salts of the subsurface ocean and the cryolave. From this new and original chemical composition, a laboratory study of several hydrolyses of tholins has been carried out. The obtained results show the formation of many organic compounds, among them, species identified only in the presence of salts. In addition, a list of potential precursors of these compounds has been established

The 'RNA World' hypothesis states that RNA was the first living system on the primitive Earth, where it carried out dual genotypic and phenotypic functions. Therefore, RNA must have self-assembled by purely chemical means from small prebiotic feedstock molecules. A plausible demonstration of the synthesis of RNA with the natural [5'→3'] phosphodiester linkage, and its self-replication has not been achieved so far. Some have speculated a 'simpler' informational polymer preceded it, and biology based on this polymer subsequently 'invented' RNA. The structurally simpler L-α-threofuranosyl nucleic acid (TNA) has been proposed as a primordial ancestor to RNA. A study into the potential self-assembly of TNA nucleotides was carried out. It is shown that as a direct result of TNA's structural simplicity, its generational chemistry is more difficult than RNA. The tetrose aminooxazolines are unstable under the conditions of its formation. The tetrose anhydronucleosides efficiently incorporate phosphate to form activated tetrose cytidine-2',3'-cyclic phosphates, but with the wrong stereochemistry. Strong support for the 'RNA world' hypothesis came from a report in 2009 of the prebiotic synthesis of activated pyridimine ribonucleoside-2',3'-cyclic phosphates. Oligomerisation studies were carried out on these activated monomers with various catalysts, and NMR studies were carried out to determine the aspects of their reactivity. It was found that only short oligomers are formed. However, nucleoside-2',3'-cyclic phosphates were found to selectively hydrolyse to a 2:1 mixture of 3' and 2'-monophosphates, and this observation was considered as etiologically relevant. Nucleoside-2' and 3'-monophosphates cyclise back to nucleoside-2',3'-cyclic phosphates upon phosphate activation, and so cannot be considered as direct candidates for oligomerisation. A chemistry that selectively uses the nucleoside-3'-phosphate for the synthesis of RNA, and recycles the unwanted 2'-phosphate would be highly desirable. Thus, a regio- and chemoselective reaction that selectively acetylates monomer and oligomer nucleoside-3'-phosphates at the 2'-hydroxyl in water is presented. Nucleoside-2'-phosphates are shown to acetylate less efficiently, and show a greater propensity to recyclise back to nucleoside-2',3'-cyclic phosphates. Purine nucleotides were also found to acetylate better than pyrimidines. This potentially primordial protecting group chemistry approach towards the prebiotic synthesis of RNA is conceptually novel, and has the potential to give a natural [5'→3'] phosphodiester linkage isomer. It is considered as a major step towards solving the long-standing problem of non-enzymatic self-replication of RNA.

Abstract available in the Current Developments in Nutrition.

A synthetic proto-organism could be self-assembled by integrating a lipid proto-container with a proto-metabolic subsystem and a proto-genetic subsystem. This three-component system can use energy and nutrients by means of either redox or photo-chemical reactions, evolve its proto-genome by means of template directed replication, and ultimately die. The evolutionary dynamics of the proto-organism depends crucially on the chemical kinetics of its sub-systems and on their interplay. In this work the template replication kinetics is investigated and it is found that the product inhibition inherent in the ligation-like replication process allows for coexistence of unrelated self-replicating proto-genes in the lipid surface layer. The combined catalytic effects from the proto-genes on the metabolic production rates determine the fate of the strain protocell.

Corn is widely used as animal feed as well as for fuel ethanol production. Fiber present in corn is not digested well by non-ruminants such as chicken and swine. Also, this fiber does not participate in conversion of starch to ethanol. Fiber separation from corn flour using the Elusieve process, a combination of sieving and air classification, would result in high starch animal feed and increase ethanol productivity. The objective of the first part of this dissertation was to understand the effect of retention screen size in the hammer mill on fiber separation from corn flour using the Elusieve process. Four different retention screen opening sizes were studied. The highest starch content of 65.2% was in the enhanced flour obtained by using 3.2 mm (8/64") retention screen; starch content of the original corn flour was 62.5%. The objective of the second part was to evaluate Elusieve process for sorghum flour. The combination of hammer milling and Elusieve process was less effective for sorghum flour compared to corn flour. The objectives of the third part were to determine the operating air velocities for corn particles and to compare physical properties of corn particles with that of Distillers’ dried grains with soluble (DDGS) particles. The operating air velocities for large, medium and small corn size fractions were 2.9 to 3.8, 2.8 to 3.0 and 2.5 to 2.6 m/s, respectively. Densities of nonfiber particles for corn flour were higher than for DDGS (earlier study). Compared to DDGS, the difference between fiber and nonfiber particle terminal velocities was higher for corn, signifying relative ease of operability for fiber separation from corn flour. The objective of the fourth part was to study the effect of corn moisture content on fiber separation. There was no effect of moisture content on fiber separation. The objective of the fifth part was to assess the economics of the Elusieve process. For ethanol plant of 50 million gallons/year capacity (50 MGY), payback period would be 3.1 years. The payback period for implementing Elusieve process in an integrated broiler operation with 8 million birds capacity would be 0.4 to 1.3 years.

Current practices support the use of probiotic and prebiotic supplementation to improve chronic gastrointestinal distress (GID). The aim of this study was to determine the tolerance and benefits of GlutenShield (GS), a prebiotic, probiotic, and enzyme supplement, on adults with GID. Subjects (n=20) took either GS or the placebo for 30 days and completed a pre-treatment FFQ as well as a pre- and post-treatment GID questionnaire, blood draw, and stool sample. Participants consumed more total and saturated fat, and less fiber and whole grains compared to the recommended intake. A significant reduction in IgG2 was observed in the GS group (p=0.008) as well as a significant reduction in self-reported bloating (p=0.038) with no change observed to cytokines or SCFAs (p>0.05). GS was well tolerated and perceived to be beneficial; however, further research is needed to identify the specific population of GID patients who could most benefit from GS supplementation.

The impact of yeasts on food production, quality and safety is closely linked with their ecology and biological activities. Recently, as a consequence of the relationship between diet and health, yeasts are becoming relevant as new probiotics or for the production of bioactive compounds. In dairy products, yeasts play a key role in proteolysis, lipolysis and lactose fermentation during cheese ripening, promoting the development of sensory properties, particularly aroma. This thesis focuses on the yeast diversity in artisanal cheeses produced in the Natural Park Serra d¿Espadà (Castelló) from ewes¿ and goats¿ raw milk. Different molecular techniques have been employed in order to characterize yeast isolates. Moreover, the succession of species along the cheese ripening process was studied. The intraspecific variability of the most abundant identified species Debaryomyces hansenii and Kluyveromyces lactis was also assessed. Additionally, the potential of Kluyveromyces marxianus and K. lactis ß-galactosidases to synthetize prebiotic oligosaccharides from lactose and lactulose was tested. Finally, Kluyveromyces and Debaryomyces isolates were investigated for the production of cheese aromatic compounds. / Padilla López, B. (2014). Yeast diversity in artisanal cheeses: biotechnological applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/36065

Gut microbiota is a key component in obesity and type 2 diabetes, yet mechanisms and metabolites central to this interaction remain unclear. We examined the human gut microbiome’s functional composition in healthy metabolic state and the most severe states of obesity and type 2 diabetes within the MetaCardis cohort. We focused on the role of B vitamins and B7/B8 biotin for regulation of host metabolic state, as these vitamins influence both microbial function and host metabolism and inflammation.

Esta tese se insere no contexto da química prebiótica, que estuda a evolução química que ocorreu antes do surgimento da vida na Terra. Tal área pertence ao ramo de pesquisa da Astrobiologia, que estuda o surgimento, a evolução, distribuição e futuro da vida na Terra ou em outro lugar do Universo. Dentre as várias hipóteses abordadas na química prebiótica, a hipótese mineral é foco de estudo deste trabalho, ou seja, se os minerais podem ter agido como preconcentradores ou protetores de moléculas biologicamente relevantes para a química prebiótica e como catalisadores de reações. A classe mineral de hidróxidos duplo lamelares (HDL) é estudada inicialmente considerando se sua síntese seria possível em um ambiente prebiótico. Desta forma, o HDL foi sintetizado por dois métodos de síntese (coprecipitação e reconstrução) e em quatro composições distintas de água do mar sintética, que mimetizam diferentes fases geológicas da Terra, os resultados mostraram a formação deste mineral em todas as composições de água do mar analisadas. Posteriormente, o estudo da interação de biomoléculas com HDL foi feito visando caracterizar se estas poderiam estar inseridas no espaço interlamelar deste mineral. O íon tiocianato, precursor de biomoléculas, e as bases nitrogenadas adenina, timina, e uracila mostraram-se presentes nas amostras de HDL sintetizadas pelos dois métodos, coprecipitação e reconstrução. As amostras foram caracterizadas por difratometria de raios X, análise termogravimétrica, análise elementar e por espectroscopia vibracional, Raman e no infravermelho. Embora os resultados iniciais indiquem que as biomoléculas possam estar interagindo com o mineral por adsorção e não necessariamente estejam intercaladas, estudos com lavagem das amostras com carbonato de sódio mostraram a troca iônica das biomoléculas pelo ânion inorgânico e sugerem que estas encontravam-se realmente no espaço interlamelar do mineral. Foram feitas então simulações de ambientes extremos nos sistemas HDL + biomoléculas para avaliar se a presença do mineral aumenta a estabilidade das biomoléculas frente a aquecimento, radiação UVC e radiação ionizante já que tais condições extremas estariam presentes na Terra primitiva / This thesis subject is related to prebiotic chemistry, which studies the chemical evolution that happened before the origin of life on Earth. This subject belongs to the Astrobiology research area, which studies the origin, evolution, distribution and future of life on Earth and elsewhere in the Universe. Among the many hypothesis that prebiotic chemistry encompass, the mineral hypothesis is the aim of this thesis, that is, if minerals could have had a role in preconcentrating and protecting molecules relevant to prebiotic chemistry, and also if they could have acted as catalists. The layered double hydroxide (LDH) minerals are studied and the first question is if they could have been synthetized in a prebiotic environment. Four different seawater compositions are analyzed, considering many geological periods of Earth, and two synthesis methods were studied: coprecipitation and reconstruction. The results showed that the LDHs are formed in all seawater types studied. Following these studies, we discuss whether biomolecules could be in the interlayer space of this mineral. Thiocyanate, a biomolecule precursor, and the nucleic acids adenine, thymine and uracil were present in the LDH samples synthetized either by coprecipitation and reconstruction, and they were characterized by X-Ray diffraction, thermogravimetric analysis, elemental analysis and by vibrational spectroscopy: IR and Raman. Although the preliminary results showed that the biomolecules are not necessarily intercalated, but may simply be adsorbed on the minerals, after washing with a sodium carbonate solution, the biomolecules were replaced by the inorganic anion, suggesting that the former was in fact intercalated in the mineral. Extreme conditions simulations were then performed on the LDH plus biomolecules systems to evaluate whether the mineral may act as a protector and stabilize the biomolecules when these were heated or irradiated with UV-C and ionizing radiation, since such scenarios would be common on early Earth

Human milk is recognized as the main component for growth, metabolism, and immune development in infants. Furthermore, during lactation, human milk is an important source of microorganisms for the intestinal colonization of newborns. Mother-related factors have been associated with the human milk microbiota composition. Nevertheless, apparently, there has not been any study in which the maternal diet was evaluated as a modulator of the human milk microbiota. Therefore, the aim of this study was to investigate the impact of the maternal diet on the human milk microbiota composition of healthy women, and subsequently, to evaluate the effect of fructooligosaccharides supplementation on the human milk microbiota. This study consisted of two parts; the first was a cross-sectional study, including 94 lactating women recruited at the University Hospital of the University of São Paulo (HU/USP), to investigate the association between the maternal nutrient intake during pregnancy and lactation over the first month and the human milk microbiota. The second part consisted of a randomized, placebo-controlled clinical trial with 53 lactating, classified as FOS group (n = 28), which received 4.5 g of fructooligosaccharides + 2 g of maltodextrin or placebo group (n = 25), which received 2 g of maltodextrin, over a period of 20 days. The DNA was isolated and used as template for amplification and sequencing by the Illumina MiSeq® System. Overall, the maternal diet during lactation (\"short-term\" food intake) influenced specific bacterial groups, including positive correlations between polyunsaturated fatty acids/linoleic fatty acids and Bifidobacterium. However, only the maternal diet during pregnancy (\"long-term\" food intake) was statistically significant (p = 0.02) for the clustering analyzes (community structure analyzes), in which higher levels of vitamin C intake during pregnancy was related to cluster 2, driven by the Staphylococcus genus. After the intervention period on the maternal diet, no differences were found for relative abundance of genera between the placebo and the FOS groups. However, the distances of the trajectories covered by the samples from the beginning to the end of the supplementation was higher for the FOS group (p = 0.0007). According to our results, the maternal age affects the response for FOS supplementation (p = 0.02), though no patterns in the differences of relative abundances were found between the groups. Our results suggest that the maternal diet may influence the human milk microbiota, and the diet during pregnancy is a stronger factor over the bacterial community structure. Minor changes were found by the maternal short-term food intake or the maternal intervention with the prebiotic, and the changes seem to be individual-dependent and influenced by the maternal age, particularly in the intervention study. / O leite humano é, reconhecidamente, o principal componente para o crescimento e o desenvolvimento metabólico e imunológico de lactentes. Adicionalmente, durante a lactação, o leite humano consiste em uma importante fonte de micro-organismos para a formação da microbiota intestinal de neonatos. Fatores relacionados à mãe têm sido associados à composição da microbiota do leite humano. Entretanto, poucos estudos avaliaram a dieta materna como componente modulador da microbiota do leite humano. Os objetivos deste estudo foram investigar o impacto da dieta materna sobre a composição da microbiota do leite humano de mães saudáveis e, posteriormente, avaliar a influência da intervenção com fruto-oligossacarídeo na microbiota do leite humano, durante 20 dias de lactação. O estudo foi dividido em duas partes; a primeira parte consistiu de um estudo transversal, com 94 lactantes atendidas no Hospital Universitário da Universidade de São Paulo (HU/USP), a fim de investigar a associação entre o consumo materno de nutrientes durante a gestação e durante o primeiro mês de lactação e a microbiota do leite humano. A segunda parte consistiu em um ensaio clínico, aleatorizado, placebo-controlado, com 53 lactantes, classificadas em grupo FOS, que recebeu 4.5 g de fruto-oligossacarídeo + 2 g de maltodextrina (n = 28) ou grupo placebo, que recebeu 2 g de maltodextrina (n = 25), suplementados por 20 dias. O DNA das amostras de leite foi isolado e utilizado como molde para amplificação e sequenciamento em Illumina MiSeq® System. Em geral, a dieta materna durante a lactação (consumo a curto prazo) apresentou influência pontual sobre diversos grupos de micro-organismos, incluindo correlações positivas entre ácidos graxos poli-insaturados/linoleico e o gênero Bifidobacterium. No entanto, somente a dieta materna durante a gestação (consumo a longo prazo) foi estatisticamente significante (p = 0.02) para as análises de agrupamento das amostras (análises de estrutura de comunidade), sendo o maior teor de vitamina C consumido durante a gestação relacionado ao agrupamento 2, direcionado por maiores populações do gênero Staphylococcus. Após o período de intervenção na dieta materna, não foram encontradas diferenças entre a abundância relativa de gêneros entre os grupos placebo e FOS. No entanto, as distâncias do percurso das amostras do início até o final da suplementação foram maiores para o grupo FOS (p = 0.0007). De acordo com os resultados, a idade materna influencia essa resposta à suplementação por FOS (p = 0.02), embora, não tenham sido encontrados padrões nítidos nas diferenças de abundância relativa entre os grupos. Os resultados obtidos sugerem que a dieta materna consiste em um fator de modulação da microbiota do leite humano, sendo a dieta durante a gestação um fator mais intenso sobre a estrutura da comunidade bacteriana do leite humano. No entanto, o consumo a curto prazo ou a intervenção alimentar com prebiótico sobre a dieta materna apresentou influência pontual sobre a dinâmica da microbiota do leite, ainda que mudanças observadas sejam indivíduo-dependentes e influenciadas pela idade materna, como no caso do estudo de intervenção.