Vitamin C is industrially produced by the Reichstein method, which uses gluconobacters to oxidize sorbitol to sorbose then a chemical process to convert sorbose to 2-keto-L-gulonic acid (2-KLG). The establishment of a more extensive microbial process for 2-KLG production translates into a less expensive and more efficient production of vitamin C. I examined pure strains and mixed cultures for their ability to produce 2-KLG using thin layer and high performance liquid chromatography. The DSM 4027 mixed culture produced the highest yield, 25 g/L, of 2-KLG from 100 g/L of sorbose, while the gram-negative rods isolated from DSM 4027 produced 8.8 g/L, and B. megaterium isolated from DSM 4027 produced 1.4 g/L. Thus, the gram-negative rods in the mixed culture were the primary 2-KLG producer, but B. megaterium in the DSM 4027 mixture enhanced this synthesis. Authentic pure cultures of Gluconobacter oxydans IFO strain 3293 and ATCC strain 621 produced 3.4 g/L and 5.7 g/L, respectively. Attempts to co-culture the isolated B. megaterium with the isolated gram-negative rods and authentic Gluconobacter strains did not increase 2-KLG production, nor did growing the cultures on B. megaterium spent media. Bacillus megaterium produced an unidentified keto-compound detected on the TLC chromatograms, which suggested that B. megaterium converted sorbose to an intermediate that may then be converted by the gram-negative rods in DSM 4027 to 2-KLG. Limited phenotypic tests suggested that the gram-negative rods in the DSM 4027 mixture are not gluconobacters. / Master of Science

Made available in DSpace on 2016-04-26T18:12:01Z (GMT). No. of bitstreams: 1 Neide Aparecida Marinho.pdf: 5671040 bytes, checksum: 981162c8959468194eaaa9ca42015b15 (MD5) Previous issue date: 2012-06-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The object of this study is the Folia Estrela do Norte , from Juiz de Fora, Minas Gerais/Brazil, from 2010 to 2011. Our main objective is to place the research of Folia de Reis , a Brazilian popular festival, in the context of recent communication studies. Through the symbols constituents of the Folias , re-investigate the meanings and usages elaborated within the communities that produce and reproduce the festivals. We seek primarily to understand how this popular ritual dialogues with the mass media. To this, we investigated the communicational aspects of the rituals. Theirs "mythologies" survive through (and despite) the industrial and digital society. Our problem: how the rituals of the Folias de Reis dialogue with the mass media? The research has shown that, in mixed cultures, flexible and mobile, the popular and the massive, the oral and the written, the open and the closed, the center and the periphery they all dialogue in tension, incorporating outside elements and breaking oppositions. We analyzed the dialogue between popular and massive, a major issue in cultures such as ours, constantly reworked from the incorporation of others, forming new cultural texts, in network and mosaic. Our main theoretical basis is the communication studies of mediations between popular culture and mass culture; how the popular and folkloric manifestations are incorporated and reworked by the cultural industry that, at the same time, provides projections and recreations? Another point is the palhaços , important characters of the Folia , and their masks that, full of representativeness, disguise, frighten and hide, allowing the man to present his "being and not being" condition. In these masks are present the legendary, the sacred and the profane, in images of grotesque that appropriate themselves of a baroque which is translated into exuberant costumes, mapping the territory of the mixed culture. Thus we find the current masking that, in a symbolic appropriation, shows the daily experiences that leave "marks", or "social masks", creating opportunities for camouflage. Contribute to our theoretical basis intellectuals of mediations theories, such as Néstor García Canclini and Jesús Martín-Barbero. From the mestizaje theories, we can mention Amalio Pinheiro, Serge Gruzinski, Peter Burke, Yuri Lotman and Laplantine / O objeto de estudo dessa pesquisa é a Folia Estrela do Oriente, de Juiz de Fora, Minas Gerais, no período entre 2010 e 2011. Nosso objetivo principal é inserir o estudo das Folias de Reis no contexto das pesquisas recentes da comunicação. Por meio das simbologias constituintes das Folias, investigamos as re-significações e as readaptações, elaboradas no seio das comunidades que produzem e reproduzem as festas. Procuramos, principalmente, compreender de que forma tal ritual popular dialoga com os meios massivos. Para tal, foram investigados os aspectos comunicacionais dos rituais. Suas mitologias sobrevivem por meio (e apesar) da sociedade industrial e digital. Nossa questão-problema é: de que maneira o ritual das Folias de Reis dialoga com a comunicação de massa? A pesquisa mostrou que, em culturas mestiças, flexíveis e móbeis, o popular e o massivo, o oral e o escrito, o aberto e o fechado, o centro e a periferia dialogam em tensão, incorporando elementos alheios e rompendo com oposições. Foi analisado, portanto, o diálogo entre o popular e o massivo, questão de suma importância em nossa cultura, constantemente reelaborada a partir da incorporação do alheio, formando novos textos em rede e mosaico. Nosso suporte teórico principal está nos estudos da comunicação que investigam as mediações entre cultura popular e de massa; como as manifestações populares e folclóricas são incorporadas e reelaboradas pela indústria cultural, que propiciam projeções e recriações simultaneamente? Outro ponto do trabalho é a figura do Palhaço, personagem importante da Folia, e suas máscaras que, carregadas de representatividade, disfarçam, amedrontam e escondem, permitindo ao homem apresentar a sua condição de ser e não ser . Nestas máscaras estão presentes o lendário, o sagrado e o profano, em estampas do grotesco que se apropriam de um barroco traduzido em exuberantes fantasias, desenhando o território do mestiço. Assim encontramos os mascaramentos atuais que, numa apropriação simbólica, mostram as experiências cotidianas que deixam marcas , ou máscaras sociais , criando possibilidades de camuflagem. Contribuem, para nossa fundamentação, pensadores da teoria das mediações, como Néstor García Canclini e Jesús Martín-Barbero. Das teorias da mestiçagem, podemos citar, Amálio Pinheiro, Serge Gruzinski, Peter Burke, Iuri Lotmam, Laplantine

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No. of bitstreams: 1 DissMB.pdf: 3232973 bytes, checksum: 2ca9f79e6634a4d39d6cb45bd3047475 (MD5) Previous issue date: 2014-03-28 / Não recebi financiamento / This work aimed to evaluated the biological hydrogen production using crude glycerol as feedstock in two anaerobic reactors: (1) anaerobic fluidized bed reactor (AFBR), that allows high mass transfer, and (2) an expanded granular sludge blanket reactor, that can used with high efficiency even at high organic loading. In the AFBR, it was evaluated the influence of HRT (14, 12, 10, 8, 6, 4, 2 and 1 hour) in the hydrogen production using crude glycerol as feedstock at 5 g.L-1 and expanded clay as support material. In the EGSB, the HRT varied from 24 to 1 hour, it was used the same feedstock as that used in the AFBR. The reactors were maintained at controlled temperature at 30°C. The noculum for AFBR and EGSB was granular sludge taken from UASB reactor treating poultry slaughterhouse that was previously submitted to heat treatment. In the AFBR, the hydrogen production rate (HPR) increased from 0.08 to 0.73L.h-1.L -1 with the decrease at HRT from 14 to 1 hour, respectively. The hydrogen yield (HY) did not presented the same trend and remained almost unchanged (0.62, 0.76, 0.73, 0.75, 0.60, 0.58, 0.69, 0.85 molH2.mol-1glycerol). For this reactor, the main byproducts were 1,3-propanediol (1,3-PD), ethanol, acetic, butyric and propionic acid. The highest 1,3-PD (1,230 mg.L-1), ethanol (723 mg.L-1), acetic acid (204 mg.L-1), propionic acid (759 mg.L-1) and butyric acid (324 mg.L-1) concentration occurred at HRT of 6, 14, 8, 2, 6 hours, respectively. In the EGSB, the HPR and the HY presented the same trend: HPR increased from 0.018 to 1.708 L.h-1.L-1 and HY increased from 0.19 to 2.87 molH2.mol-1glycerol with the decrease in the HRT from 14 to 1 hour. For both reactors, the AFBR and the EGSB,the highest HPR and HY occurred at HRT of 1 hour. As well as for the AFBR, the main byproducts quantified in the EGSB were 1,3-propanediol (1,3-PD), ethanol, acetic, butyric and propionic acid. The highest 1,3-PD (1,606 mg.L -1), ethanol (400 mg.L-1), acetic acid (219 mg.L-1), propionic acid (1,075 mg.L-1) and butyric acid (248 mg.L-1) concentration occurred at HRT of 16, 12, 16, 8, 20 hours, respectively. / O presente estudo avaliou a produção biológica de hidrogênio utilizando glicerol bruto como matéria-prima em dois reatores anaeróbios: (1) reator anaeróbio de leito fluidizado (RALF), que possibilita elevada transferência de massa, e (2) um reator de leito granular expandido (EGSB), que pode apresentar alta eficiência mesmo quando aplicadas elevadas cargas orgânicas. No RALF, foi avaliada a influência do TDH (14, 12, 10, 8, 6, 4, 2 e 1 hora) na produção de hidrogênio utilizando o glicerol bruto como matéria-prima na concentração de 5 g.L-1 e argila expandida como material de suporte. No EGSB, o TDH estudado variou de 24 a 1 hora, e o substrato e a concentração foram as mesmas que os utilizadas no RALF. Os reatores foram mantidos em temperatura controlada de 30 °C. O inóculo para ambos os reatores, RALF e EGSB, foi lodo granular de reator UASB utilizado no tratamento de água residuária de abatedouro de aves, que foi previamente submetido ao tratamento térmico. No RALF, a taxa de produção de hidrogênio (HPR) aumentou de 0,08 para 0,73L.h-1.L- 1 com a diminuição do TDH de 14 para 1 hora, respectivamente. O rendimento de hidrogênio (HY) não apresentou a mesma tendência e manteve-se praticamente inalterado (0,62; 0,76; 0,73; 0,75; 0,60; 0,58; 0,69 e 0,85 molH2.mol-1glicerol) . Para este reator, os principais metabólitos foram 1,3-propanodiol (1,3-PD), etanol, ácido acético, butírico e propiônico. A maior concentração de 1,3- PD (1.230 mg.l-1), etanol (723 mg.L -1 ), ácido acético (204 mg.L-1), ácido propiônico (759 mg.L-1) e ácido butírico (324 mg.L-1) foi observada nos TDH de 6, 14, 8, 2, 6 horas, respectivamente. No EGSB, o HPR e HY apresentaram a mesma tendência: o HPR aumentou de 0,018-1,708 L.h-1.L-1 e o HY aumentou de 0,19-2,87 molH2.mol-1 glicerol com a diminuição do TDH de 14 para 1 hora. Para ambos os reatores, o RALF e o EGSB, a maior HPR e o maior HY foram observados no TDH de 1 hora. Assim como para o RALF, os principais metabólitos quantificados no EGSB foram 1,3- propanodiol (1,3-PD), etanol, ácido acético, ácido butírico e ácido propiônico. A maior concentração de 1,3- PD (1.606 mg.L-1), etanol (400 mg.L -1), ácido acético (219 mg.L-1), ácido propiônico (1.07 mg.L -1) e ácido butírico (248 mg.L -1) foi observada no TDH de 16, 12, 16, 8 e 20 horas, respectivamente.

This thesis investigates the effects of co-culturing microorganisms including 37 yeast, 38 bacteria, nine diazotrophic cyanobacteria, and three fungi on biomass and lipid production in fresh- and saltwater algae. Algal lipid content was measured using Nile Red method and gravimetric techniques. Among the algal strains tested, freshwater Coelastrum sp. 46-4, and saltwater Cricosphaera sp. 146-2-9, showed enhanced biomass yield and lipid content in response to co-culture with bacteria, cyanobacteria, and fungi. While co-culture with yeast caused inhibition of algal productivity, no difference in algal productivity was observed between nitrogen-free diazotrophic cyanobacterial co-culture and nitrogen-replete monoalgal culture. Results indicated that extracellular compounds from the freshwater bacteria Pseudomonas stutzeri and marine fungus Fusarium sp. significantly account for stimulation of lipid accumulation within algal cells, while co-cultivation with live microorganism cells stimulated biomass production in algae.

L’objectif de ce travail a été de développer un procédé performant de production d’acide lactique par Lactobacillus casei subsp. rhamnosus sur jus de datte. Dans une première partie, des cultures en mode discontinu ont été réalisées afin d’étudier les besoins nutritionnels de la souche. Ces études ont pour but de décrire les effets des sources carbonées, azotées et les vitamines sur la production d’acide lactique. Nous avons montré que le sulfate d’ammonium est une bonne alternative économique et nous avons pu déterminer la faisabilité de minimiser l’ajout de l’extrait de levure par l’utilisation partielle de l’extrait de levure combinée avec du sulfate d’ammonium plus l’ajout de vitamines du groupe B. Des cultures pures et mixtes de Lactobacillus casei et Lactococcus lactis ont été réalisées. Le système de culture mixte donne de meilleurs résultats concernant la production d’acide lactique et l’utilisation des sucres comparés à ceux obtenus en cultures pures de Lactobacillus casei ou Lactococcus lactis. L’effet des sucres purs (glucose et fructose) et mixtes (glucose/fructose) sur la production d’acide lactique a été étudié. La production d’acide lactique est plus importante avec un mélange de sucres qu’avec des sucres non mélangés ce qui explique les performances de fermentation sur jus de datte. Dans une seconde partie, une stratégie d’alimentation du réacteur en culture semi-continue a été mise en œuvre, permettant d’améliorer les performances de la fermentation. Les deux facteurs influençant le bon fonctionnement sont le débit et la concentration du milieu d’alimentation. Dans une troisième partie, une étude cinétique a été développée en réacteurs continus. Nous avons étudié l’influence du taux de dilution sur la croissance, l’utilisation du substrat et la production d’acide lactique. La productivité du procédé continu a été considérablement augmentée en comparaison avec le procédé discontinu. Enfin, dans une dernière partie, un modèle a été établi. Ce modèle, bien qu’imparfait, permet apparemment de simuler la croissance, la consommation des sucres de jus de datte et la production d’acide lactique en culture discontinue / The aim of this work was to develop an efficient process of lactic acid production by Lactobacillus casei subsp. rhamnosus on date juice In a first part, the batch cultures were realized to carry out the nutritional requirement of the strain. These studies allowed us to describe the effects of carbon substrates, nitrogen substrates and vitamins on the lactic acid production. We showed that ammonium sulphate is a satisfying economic alternative and we have determined feasibility of minimizing the addition of the yeast extract by the partial use of yeast extract combined with the ammonium sulphate plus the addition of vitamins of the group B. Pure and mixed cultures of Lactobacillus casei and Lactococcus lactis were carried out. The mixed system gives better results concerning the lactic acid production and the use of the sugars compared with those obtained in pure cultures of Lactobacillus casei or Lactococcus lactis. The effect of pure sugars (glucose and fructose) and mixed sugars (glucose/fructose) on the lactic acid production was studied. The lactic acid production is more important on mixed sugars than on pure sugars what explains the performances of fermentation on date juice. In a second part, a mode of fed batch operations was defined to improve the performances of the fermentation. The two factors influencing the process are the feeding rate and the concentration of the feeding medium. In a third part, kinetic study in continuous culture was developed. We studied the influence of dilution rate on growth, substrate utilization and lactic acid production. The productivity of the continuous process was considerably increased in comparison with the batch process. Finally, a tentative model has been established for the fermentation process. The corresponding model, although not perfect, is apparently able to simulate growth rate, substrates uptake and lactic acid production in batch culture

De nos jours, les cultures mixtes sont considérées comme une sérieuse alternative aux cultures pures pour les procédés de biotechnologie. En effet, les cultures mixtes peuvent fonctionner en réacteur continu, dans des conditions non-stériles et traiter une grande variété de substrats organiques. La principale restriction de l'utilisation de ces bioprocédés en cultures mixtes réside dans leur instabilité liée à la présence de voies métaboliques non désirées résultant d'interactions microbiennes complexes. Notamment, le rôle des bactéries de faible abondance reste à être élucidé. Ce travail a donc consisté, dans un premier temps à déterminer le rôle des bactéries minoritaires dans la production d'hydrogène par voie fermentaire en utilisant un chémostat alimenté en continu avec un milieu à base de glucose. Sept inocula ont été cultivés dans les mêmes conditions opératoires. De façon remarquable, Clostridium pasteurianum a été retrouvé comme espèce dominante de l'écosystème six fois sur sept. Seules la nature et la diversité des espèces minoritaires variaient d'un écosystème à l'autre. Ainsi, il a été montré que la structure des communautés microbiennes a une influence significative sur la production de bio-hydrogène. Au sein de ces communautés, les bactéries en proportion minoritaires jouent un rôle clé en orientant le métabolisme globale de l'écosystème. La deuxième étape de ce travail a consisté à utiliser certaines de ces espèces minoritaires comme Ingénieurs Ecologiques des Ecosystèmes microbiens (IEEM). Pour cela, la structure d'une communauté microbienne productrice d'hydrogène a été modifiée artificiellement en introduisant des souches bactériennes exogènes aux fonctions redondantes et/ou complémentaires des souches indigènes. Les résultats en réacteur batch ont montré que les performances de production d'hydrogène pouvaient être améliorées jusqu'à un facteur 3,5 par l'ajout de certaines souches. Dans l'ensemble, les résultats obtenus ne peuvent être expliqués par de simples interactions trophiques et suggèrent la présence de mécanismes d'interactions de coopération entre microorganismes. De plus, sous des conditions opératoires plus favorables (inoculum, milieu), l'insertion de certaines espèces minoritaires a permis plutôt de stabiliser le métabolisme de l'écosystème microbien sans pour autant en affecter favorablement la production d'hydrogène. Dans tous les cas, les interactions compétitives n'ont pas été favorables à la production d'hydrogène. Enfin, des essais en réacteur continu ont montré que le mode d'implantation des souches peut être un facteur primordial pour l'utilisation d'IEEM. En conclusion, ce travail a montré la potentialité d'utiliser des bactéries exogènes, en proportions minoritaires, comme facteurs biotiques pour stabiliser et/ou orienter les métabolismes microbiens vers des fonctions d'intérêt au sein des cultures mixtes microbiennes. / Nowadays mixed cultures are considered as a serious alternative to pure cultures in biotechnological processes. Mixed cultures can be operated continuously, under unsterile conditions and from various organic substrates. One of the most constraints remains the chronic instability of the mixed culture processes due to the presence of unwanted metabolic pathways resulting from complex microbial interactions. More particularly the role of bacteria in low abundance remains to be elucidated. Therefore this work consisted initially to determine the contribution of sub-dominant bacteria to fermentative hydrogen production using a chemostat continuously fed with a glucose-based medium. Seven inocula were grown under the same operating conditions. Interestingly, Clostridium pasteurianum was found as dominant in six assays on seven at steady state. Only the minority bacterial population differed with regards to their identity and diversity. Acting as true keystone species, these minority bacteria impacted substantially the metabolic network of the overall ecosystem despite their low abundance. In a second step, this work consisted in using some of these minority species as Ecological Engineers of Microbial Ecosystem (EEME). In order to study this aspect, the structure of a hydrogen-producing microbial community has been artificially modified by adding exogenous bacterial strains with redundant functions and/or complementary native strains. Results in batch reactors have shown that the hydrogen production performances could be improved to a 3.5 factor by the addition of certain strains. Results obtained can not be explained by simple trophic interactions and suggest the presence of interaction mechanism of cooperation among microorganisms. Moreover, under more favourable operating conditions (inoculum, culture medium), the addition of certain species in low abundance could stabilize the metabolism of microbial ecosystem without necessarily favourably affect the hydrogen production. In all cases, competitive interactions were not favourable for hydrogen production. Trials were then realised in continuous reactors. These trials have shown that the method used to implant strains in reactors could be a key factor for using the EEME.As a conclusion, this study has shown the potential to use exogenous bacteria, in minority proportions, as biotic factors to stabilised and/or guides microbial metabolisms to functions of interest within microbial mixed cultures.

La Fermentation Malo-Lactique (FML) réalisée par OEnococcus oeni est une étape importante de la vinification qui doit être maîtrisée. Bien que les vinificateurs aient à leur disposition des souches OE. oeni selectionnees la FML n’est pas toujours réussie. Les conditions physico-chimiques (pH, éthanol, température), la composition du vin et les facteurs biologiques influencent l’activite de cette bacterie ; parmi ces dernières les interactions entre micro-organismes sont primordiales. Souvent, après la fermentation alcoolique par la levure, des souches indigenes d’OE. oeni sont naturellement présentes dans le vin. Des interactions négatives peuvent alors se produire entre les souches autochtones et les souches sélectionnées apportées. Des connaissances sur ces interactions sont donc necessaires. L’objectif de ce travail etait d’etudier les interactions pendant la FML entre 5 souches d’OEnococcus oeni issues de différentes niches écologiques. Pour cela, des expériences ont été effectuées dans du milieu MRS modifié et dans des conditions proches à celles du vin (20 °C ; pH 3,5 et 10 % d’ethanol). Nous avons tout d’abord caracterise le comportement des souches en cultures pures à la fois dans les conditions de micro-aerobie et d’anaerobiose. Une grande variabilité a été retrouvée entre les souches dans les 2 conditions : trois des 5 souches sont favorisées en conditions d’anaerobiose tandis que les deux autres se sont mieux développées en conditions de micro-aérobie. La présence de 4 g.L-1 d’acide L-malique dans le milieu permet de produire, pour toutes les souches, une biomasse environ 2 fois plus élevée que celle obtenue dans le milieu sans acide L-malique. La totalite de l’acide malique est consommee par les 5 souches mais avec des vitesses différentes. Pour une souche donnée la vitesse spécifique de consommation d’acide L-malique (ν) et la vitesse specifique de croissance (μ) presentent des profils similaires au cours de la FML. Elles ont été reliées par un modèle mathématique qui a permis de quantifier ce lien pour chaque souche. Les interactions lors des cultures mixtes des 10 couples formés par les 5 souches ont ensuite été étudiées dans un Bio-Réacteur à Membrane (BRM) en anaérobiose. Trois catégories ont été mises en évidence: interactions à effets négatifs réciproques sur la croissance des 2 souches en culture mixte ; interactions à effet négatif sur la croissance de la souche la plus rapide en culture pure et à effet positif sur la croissance de la souche la plus lente en culture pure et interactions à effets positifs sur la souche la plus rapide en culture pure. La comparaison des cultures pures et mixtes a révélé que l’activite specifique de croissance des souches est affectee en culture mixte, ce qui provoque le prolongement de la phase de la latence dans le cas de l’inhibition et son raccourcissement dans le cas de la stimulation. La modelisation de la consommation d’acide L-malique a révélé pour certains couples une activation de la consommation de cet acide bien que la croissance soit fortement inhibée. Ces interactions, qui affectent le déroulement de la FML, ne peuvent etre dues qu’a l’effet de metabolite(s) extracellulaire(s) excretee(s) dans le milieu de fermentation. Ces métabolites restent à identifier. / In winemaking, the control of malolactic fermentation (MLF) by OEnococcus oeni is an essential step for this process. Although winemakers have the availability for selected OE.oeni strains, the MLF is not always successful. The physical-chemical conditions (pH, ethanol, and temperature), the composition of wine, and biological factors, all together influence the activity of this bacterium; regarding biological factors, the interactions between microorganisms are essential. Often, after alcoholic fermentation by yeast, indigenous strains of OE.oeni are naturally present in wine, negative interactions can then occur between the indigenous strains and selected strains; therefore, knowledge on these interactions is needed. The goal of the present work was to study the interactions during MLF between five strains of OE.oeni from different origins. Experiments were performed in the modified MRS medium to be in nearly conditions to those of wine (20 °C, pH 3.5, and 10% ethanol). The characterization of the behavior of strains in pure cultures was done under both, micro-aerobic and anaerobic conditions; a large variability was found between the strains in the two conditions: three out of five strains were favored under anaerobic conditions while the two others were better developed in micro-aerobic conditions. The presence of 4 g.L-1 of L-malic acid in the culture medium increased the biomass produced, about two-fold higher than that obtained in medium without L-malic acid. All of the L-malic acid is consumed by the five strains but at different specific rates. A mathematical model allowed to quantifying the relationship between the specific consumption rate of L-malic acid (ν) and the specific growth rate two specific rates for each strain; for a given strain, both rates have similar profiles during the MLF. Interactions in mixed cultures of 10 couples formed by the five strains were then examined in a Membrane Bioreactor (BRM) under anaerobic conditions. Three different interaction types were identified: 1) negative reciprocal interactions of the both strains in mixture culture, 2) interaction that affect negatively the favored strain in pure culture and positively the slowest one, and 3) interaction with positive effect on the fastest strain in pure culture. Comparison of pure and mixed culture showed that the specific activity of strains was affected in mixture culture causing the extension of the lag phase in the case of inhibition and its shortcut in the case of stimulation. Modeling of the consumption of the L-malic acid revealed activation of the consumption of this acid for some couples however, growth is strongly affected. The interactions affecting the course of the MLF are due solely to the effect of excreted extracellular metabolite(s); these metabolites remain to be identified

La levure et la microalgue sont des microorganismes très étudiés pour la production de composés à haute valeur ajoutée pour des secteurs tels que l’agroalimentaire et l’énergie. Ce travail de thèse propose un procédé de culture mixte entre la levure Saccharomyces cerevisiae et la microalgue Chlorella vulgaris pour la croissance des deux espèces tout en limitant le rejet en CO2. Le procédé repose sur la symbiose mutuelle entre les deux organismes autour des échanges de gaz, qui est rendu possible en imposant une co-dominance en termes de population. Les populations doivent être équilibrées pour que les microalgues puissent gérer la production de CO2. Le procédé est réalisé en photo-bioréacteur de 5 litres non-aéré et fermé, afin d’éviter les échanges gazeux avec l’environnement externe. Dans cette configuration, le CO2 est produit sous forme dissoute et directement accessible aux microalgues, évitant les phénomènes de dégazage et de dissolution. Les populations de levures et de microalgues atteignent une concentration égale (20 millions de cellules par ml) au bout de 24 heures de culture, restent stables jusqu’à la fin de la culture (168 heures) et les microalgues recyclent 12% du CO2 produit par les levures. Un modèle cinétique de la levure et de la microalgue en culture mixte est développé en combinant les modèles individuels de la levure et de la microalgue. Le modèle prédictif de la levure prend en compte les possibles voies métaboliques impliquées dans la fermentation et la respiration de ces voies est prédite en y intégrant des facteurs de limitation. Le modèle de la microalgue est basé sur l’activité photosynthétique. Les résultats de ce travail montrent la faisabilité du procédé de culture mixte entre hétérotrophe et autotrophe et pourrait apporter les bases pour le développement d’un procédé écologique à faible impact environnemental. / Yeast and microalgae are microorganisms widely studied for the production of high-value compounds used in food and energy area. This work proposes a process of mixed culture of Saccharomyces cerevisiae and Chlorella vulgaris for both growth and CO2 mitigation. The process relies on mutual symbiosis between the two organisms through gas exchange, which is possible by engineering the co-dominance of populations. The two populations must be balanced in such a way so that microalgae can cope with the rate of CO2 production by the yeast activity. The process is performed in non-aerated 5l-photo-bioreactor fitted with a fermentation lock to prevent gas exchange with the outside atmosphere. With this set-up, the CO2 is produced in dissolved form and is available to the microalgae avoiding degassing and dissolution phenomena. The two organism populations are balanced at approximately 20 millions cells per ml, 12% CO2 produced by yeast was reutilized by microalgae within 168 hours of culture. A yeast and microalgae growth model in mixed culture is developed by combining each individual growth model. The predictive yeast model considers the possible metabolic pathways involved in fermentation and respiration and imposes limitation factors on these pathways, in this manner, the model can predict the partition of these pathways. The microalgae individual model is based on the photosynthetic activity. The results of this work show the feasibility of such process and could provide a basis for the development of a green process of low environmental impact.

Polyhydroxyalkanoates (PHAs) are a group of bioplastics, which are produced through microorganisms. They are accumulated in granules inside bacteria’s cell cytoplasm and serve as an energy reserve. Moreover, PHAs are completely biodegradable and biocompatible biopolyesters, which make them to suitable materials for medical applications and replace conventional petrochemical plastics. However, it is not economically feasible to produce PHAs yet, as it is four to nine times as expensive as to produce fossil fuel-based plastics. In order to reduce the price, it is possible to use waste streams rich in carbon and mixed cultures as microorganisms, which was applied in this thesis work. In this study, PHAs were synthesized from a volatile fatty acid (VFA) mixture rich in hexanoic acid, which was produced by anaerobic digestion of waste streams. To be able to obtain the maximum PHA content, the experimental work was separated into a selection phase and a production phase respectively. During the selection step, enrichment of the mixed culture took place during 50 days altering feast/famine cycles. The production phase was then conducted in a fed-batch cultivation to accumulate as much PHAs as possible, while utilizing the enriched mixed culture.  The selection phase was seen as successful since the quantity of synthesized PHA increased with time. Solely polyhydroxybutyrate (PHB) was formed during this period. The specific consumption rates for the hexanoic acid and acetic acid were almost the same in this phase (0.10 g hexanoic acid/(g volatile suspended soilds (VSS),h) and 0.11 g acetic acid/(g VSS,h)), which suggests that the consumption of these majoritarian fatty acids was simultaneous. However, the determined consumption rate for butyric acid was approximately solely half of the values for hexanoic acid and acetic acid. The highest PHA yield obtained in the enrichment phase was 0.26 g PHB/g VFA.  In the production phase, the highest achieved PHA content was 31.4 % of VSS, which was obtained after five hours. Both PHB and polyhydroxyvalerate (PHV) were formed in this phase, even though the quantity of accumulated PHB dominated with its approximately 97 weight-%. / Polyhydroxialkanoater (PHA:er) är en grupp bioplaster som produceras med hjälp av mikroorganismer. De ackumuleras inuti granulater som finns i bakteriers cellcytoplasma, och används som en energireserv. PHA:er är dessutom fullständigt bionedbrytbara och biokompatibla biopolyestrar, vilket gör dem till lämpliga material att applicera inom medicinska preparat och för att ersätta konventionella petrokemiska plaster. Det är däremot inte ekonomiskt fördelaktigt att producera PHA:er än så länge, då det är fyra till nio gånger dyrare att producera än i jämförelse med att producera plaster från fossila bränslen. Ett tillvägagångssätt för att reducera priset är genom att applicera kolrikt avfall som råmaterial och en blandad kultur av mikroorganismer. Det var detta som tillämpades i detta examensarbete vid PHA produktionen. I denna studie syntetiserades PHA:er från en blandning av flyktiga fettsyror rik på hexansyra, som framställts av avfall genom anaerobisk digestion. Det experimentella arbetet delades in i två faser: en selektionsfas och en produktionsfas. Detta för att kunna erhålla högsta möjliga PHA innehåll. Den blandade kulturen av bakterier berikades under selektionsfasen genom applicering av alternerande svält/frossa cykler i 50 dagar. Produktionsfasen utfördes därefter i en så kallad ”fed-batch odling” för att ackumulera högsta möjliga kvantitet av PHA, med hjälp av den berikade kultur blandningen.  Selektionsfasen ansåg vara lyckad, då mängden ackumulerad PHA ökade med tiden. Endast polyhydroxibutyrat (PHB) producerades under berikelsefasen. De erhållna specifika konsumptionshastigheterna för hexansyra och ättiksyra var i samma storleksordning (0.10 g/(g flyktiga suspenderade ämnen, h) respektive 0.11 g/(g flyktiga suspenderade ämnen, h)), vilket tyder på att förbrukningen av dessa fettsyror skedde samtidigt. Konsumptionshastigheten för butansyra var däremot endast cirka hälften av hastigheterna för hexansyra samt ättiksyra. Det högsta PHA-utbytet beräknades till 0.26 g PHB/g flyktiga fettsyror. Det högsta PHA-innehållet som erhölls i produktionsfasen var 31.4 % av de flyktiga suspenderade ämnena, vilket uppmättes efter fem timmar. Både PHB och polyhydroxivalerat (PHV) bildades under denna fas, även om mängden ackumulerad PHB dominerade med 97 vikt-%. / <p>I och med COVID-19 presenterades examensarbetet via zoom</p> / Carbon Neutral Next Generation Wastewater Treatment Plants

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / This work was to study the influence of the magnetic field on the reduction of hexavalent chromium, removal of COD and total chromium, addition of cell growth in batch (batch reactor), using a mixed culture from located in a tanning city of Franca-SP (AMCOA). The influence of static magnetic field generated by a device that produces an electric current through a conductor, producing a magnetic field around the conductor, like a magnet. This equipment produces a magnetic field pulsed square wave of constant intensity and frequency. In the first step of adjusting the mixed cultures of chromium VI obtained a promising response. Thereafter, a preliminary test was performed to analyze the behavior of the influence of the magnetic field in the reduction of chromium VI and diameter of the reactor, obtaining 71% reduction of chromium VI with a larger diameter, without the presence of magnetic field has seen a reduction of 53%, with an initial concentration of 100 mg/l of chromium and a time of 4 hours of process. In other stages of the project, performing the tests with different frequencies of the magnetic field (1,2,5 and 10 Hz) and doing an analysis related to cell death of micro-organisms, showed that for frequencies of 10 Hz, there was cell death presents some cultures, which was confirmed in a lower frequency. The results were satisfactory when used in a magnetic field frequency of 5 Hz, maximal reduction of chromium VI reducing the time about 4 hours of processing, better removal of COD and total chromium using a volume of 500 ml and concentration of 100 mg/l initial chromium. Checking the influence of different frequency magnetic field, the initial effluent volumes (300 and 1000 ml) and initial concentration of chromium VI (50, 150 and 200 mg/l). The higher the initial concentration the lower the chromium reduction of chromium VI, larger volumes and a reduction of chromium VI and removal of COD and total chromium is not as significant as the use of smaller volumes. / Neste trabalho foi realizado o estudo da influência do campo magnético sobre a redução de cromo hexavalente, remoção de cromo total e DQO, além do crescimento celular em modo descontínuo (reator batelada), utilizando-se de uma cultura mista proveniente do curtume AMCOA localizado na cidade de Franca-SP. Foi avaliada a influência de campo eletromagnético estático gerado por um equipamento que produz uma corrente elétrica, passando por um condutor, produzindo um campo magnético ao redor do condutor, como se fosse um ímã. Este equipamento produz um campo magnético pulsante com onda quadrática de intensidade e frequência constantes. Na primeira etapa de adaptação das culturas mistas ao cromo VI obteve-se uma resposta promissora. Posteriormente, foi realizado um teste preliminar para analisar o comportamento da influência do campo magnético na redução de cromo VI e diâmetro de reator, obtendo 71% de redução de cromo VI com um maior diâmetro, sem a presença de campo magnético obteve uma redução de 53%, com uma concentração inicial de 100 mg/L de cromo e com um tempo de 4 horas de processo. Nas outras etapas do projeto, realizando os testes com diferentes frequências de campo magnético (1, 2, 5 e 10 Hz) e fazendo uma análise relacionada à morte celular dos micro-organismos, mostrou-se que para frequências de 10 Hz, havia morte celular de algumas culturas presentes, o que não foi verificado em uma frequência menor. Os resultados foram satisfatórios quando se utiliza uma frequência de campo magnético de 5 Hz, com máxima redução de cromo VI reduzindo o tempo em torno de 4 horas de processo, com melhor remoção de cromo total e DQO, utilizando um volume de 500 mL e concentração de 100 mg/L de cromo inicial. Verificando a influência de diferentes frequências de campo magnético, volumes iniciais de efluente (300 e 1000 mL) e concentrações iniciais de cromo VI (50, 150 e 200 mg/L). Quanto maior a concentração inicial de cromo menor foi a redução de cromo VI, e em volumes de efluentes maiores a redução de cromo VI e remoção de cromo total e DQO não foram tão significativas quanto em se aplicar volumes menores. / Mestre em Engenharia Química