Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Grape must gives rise to various stress conditions for the yeast inoculated for alcoholic fermentation. These include hyperosmotic stress due to the high initial sugar concentration and redox imbalances due to the fast depletion of oxygen. Under these stress conditions, Saccharomyces cerevisiae tends to produce glycerol as an osmoprotectant and to regenerate reducing equivalents. However, the production of glycerol often leads to increased acetic acid production. According to literature, it seems that many non-Saccharomyces yeasts have a different metabolic response to the above-mentioned stress conditions, especially since it has been found that they produce low levels of acetic acid. Only recently non-Saccharomyces yeasts were researched to be used as starter cultures in wine fermentations. It is found that they can confer beneficial characteristics to the resulting wine. However, most of the non-Saccharomyces yeasts lead to stuck fermentations as confirmed by this study. Therefore, if the positive characteristics of these yeasts were to be exploited in wine making they need to be inoculated together with S. cerevisiae. When two yeasts are inoculated together, they affect each other and consequently the wine. In this context, the aim of this study was to investigate the metabolic response to hyperosmotic stress during wine fermentation of the following wine-related non-Saccharomyces yeasts: Lachancea thermotolerans, Torulaspora delbrueckii and Starmerella bacillaris. Fermentations were performed in a synthetic grape must medium with pure cultures of the mentioned strains as well as mixed cultures of each non-Saccharomyces yeast with S. cerevisiae. The fermentation behaviour was monitored and concentrations of various wine-related metabolites were determined. Concerning polyol concentrations, S. cerevisiae produced only glycerol while the non-Saccharomyces yeasts also produced other polyols. The low production of acetic acid in the non-Saccharomyces fermentations was confirmed especially in the case of L. thermotolerans. Moreover, this yeast produced high levels of the higher alcohols butanol and propanol. St. bacillaris produced significant levels of acetoin and isobutyric acid and T. delbrueckii produced an increased concentration of succinic acid. All these metabolites might play a role in maintaining intracellular redox balance. However, a more extensive systematic study is needed to investigate the extent of their involvement. The mixed cultures completed fermentation and had higher final glycerol levels than the control and lower acetic acid concentrations and therefore can contribute positively to the wine aroma. Furthermore, the mixed culture fermentations showed the potential of lowering the ethanol concentrations of wine. Furthermore it has been shown in literature that the yeasts present in the mixed culture can affect each other on gene expression level as well. However, there is little genetic information available on non-Saccharomyces yeasts. In this study, we sequenced the genes involved in glycerol and acetic acid biosynthesis of L. thermotolerans and T. delbrueckii. The gene sequences are fairly homologous with only a few differences. These gene sequences can be used to study gene expression of GPD1 and ALD6 from fermentation samples in order to determine to what extent the yeasts in a mixed culture influence the gene expression of one another. / AFRIKAANSE OPSOMMING: Druiwemos gee oorsprong aan verskeie strestoestande vir die gis wat vir alkoholiese fermentasie geïnokuleer word. Hierdie strestoestande sluit hiper-osmotiese stres, as gevolg van die hoë suiker konsentrasie, in asook redoks wanbalanse toegeskryf aan die vinnige afname in beskikbare suurstof. Tydens hierdie toestande is Saccharomyces cerevisiae geneig om gliserol as beskerming teen die osmotiese stres te produseer, sowel as vir die regenereering van reduserings ekwivalente. Die produksie van gliserol lei egter dikwels tot toenemende asynsuur produksie. Volgens literatuur kom dit voor asof menige nie-Saccharomyces giste 'n ander metabolise reaksie tot die bogenoemde stresse het, omdat daar gevind is dat hulle laer vlakke van asynsuur produseer. Eers onlangs is navorsing gedoen op die potensiële gebruik van nie-Saccharomyces giste in gemengde kulture tydens wynfermentasies. Daar is bevind dat hulle voordelige eienskappe aan die wyn kan verleen. Meeste van die nie-Saccharomyces giste lei egter tot onvolledige fermentasies soos bevesting deur hierdie studie. Dus, indien die positiewe eienskappe van hierdie giste sou benut word in wynmaak sal hulle saam met S. cerevisiae geïnokuleer moet word. Wanneer twee giste saam geïnokuleer word, beïnvloed hulle mekaar en gevolglik die wyn. In hierdie konteks was die doel van die betrokke studie om die metaboliese reaksie tot hiperosmotiese stress tydens wynfermentasies te ondersoek in die volgende wyn verwante nie-Saccharomyces giste: Lachancea thermotolerans, Torulaspora delbrueckii en Starmerella bacillaris. Fermentasies was in sintetiese druiwemos medium uitgevoer met rein kulture van die genoemde gisrasse, sowel as gemengde kulture van elke nie-Saccharomyces gis met S. cerevisiae. Die fermentasiegedarg is gemonitor en die konsentrasies van verskeie wyn verwante metaboliete is bepaal. Wat die poliol konsentrasies betref, het S. cerevisiae slegs gliserol geproduseer terwyl die nie-Saccharomyces giste additionele poliole ook geproduseer het. Die lae produksie van asynsuur in die nie-Saccharomyces fermentasies is bevestig, veral in die geval van L. thermotolerans. Verder produseer hierdie gis hoë vlakke van asetoïen en iso-bottersuur en T. delbrueckii produseer 'n hoër konsentrasie van suksiensuur. Al hierdie metaboliete mag 'n rol speel in die handhawing van intrasellulêre redoksbalans. 'n Meer uitgebreide, sistematiese studie is egter nodig om die mate van hul betrokkenheid te ondersoek. Die gemengde kulture het hul fermentasies voltooi en het hoër finale gliserol vlakke as die kontrole gehad, asook laer asynsuur konsentrasies en kan dus positief bydra tot die wyn aroma. Verder het die gemengde kultuur fermentasies die potensiaal om die etanol vlakke van wyn te verlaag, getoon. Daar is verder in die literatuur gevind dat die giste teenwoordig in die gemengde kultuur mekaar op geenuitdrukkings vlak ook kan beïnvloed. Daar is egter min genetiese inligting beskikbaar vir die nie-Saccharomyces giste. In hierdie studie het ons die gene betrokke by die produksie van gliserol en asynsuur van L. thermotolerans en T. delbrueckii se nukleotied volgordes bepaal. Die gevolglike nukleotied volgordes is redelik homoloog met net 'n paar verskille. Hierdie volgordes kan gebruik word om die geenuitdrukking van GPD1 en ALD6 vanaf fermentasie monsters te bestudeer om sodoende te bepaal tot watter mate die giste in 'n gemengde kultuur mekaar se geenuitdukking kan beïnvloed.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The use of non-Saccharomyces yeasts together with the yeast S. cerevisiae in multistarter wine fermentations has emerged as a useful tool to modulate wine aroma and/or to decrease the concentration of undesirable compounds. However, upon inoculation, these yeast species do not co-exist passively, but interact in various ways. While competition for nutrients and the excretion of killer toxins in an antagonistic relationship are obvious and well established types of interactions, some studies have suggested the existence of other forms of cellular or molecular interactions. One of these includes physical cell-cell contact and to our knowledge, only one previous study has confirmed its existence in wine yeasts. Yeast interactions are also influenced by other factors, such as ethanol concentration, however some studies have highlighted the role that dissolved oxygen plays on the survival of non-Saccharomyces yeasts and their ability to compete for space with S. cerevisiae and little research has focused on this. This study aimed to investigate the occurrence of a physical cell-cell and/or metabolic interaction between S. cerevisiae and L. thermotolerans in mixed culture fermentations of synthetic grape must. For this purpose, fermentations in a Double Compartment Bioreactor (DCB) which separates yeast population through the use of a membrane were compared to mixed fermentations in the absence of the membrane, using the same reactor. Furthermore, the impact of oxygen supply on yeast behaviour was also assessed. Following mixed culture fermentations in a DCB, it was observed that the presence of S. cerevisiae led to a significant decline in viability in L. thermotolerans. This decline was significantly less prominent in mixed cultures where the cells were in indirect contact. Together, the data provided evidence for both cell-cell and metabolic interactions whereby S. cerevisiae had a strong negative influence on the growth of L. thermotolerans. However, it was also observed that L. thermotolerans had some negative impact on the growth of S. cerevisiae, leading to a reduction in biomass (when in indirect contact) and a reduced maximum CFU/mL compared to pure cultures. The data also suggest that direct physical contact may increase the production of glycerol and propanol, but this needs further investigation. By decreasing the frequency at which oxygen pulses were provided, a reduction in biomass and increase in fermentation duration was observed for all fermentations. However, this effect was somewhat reduced in mixed cultures. Here, no impact on fermentation duration was observed and the decrease in biomass was less compared to pure cultures. The impact of these oxygen pulses was also greater on L. thermotolerans. In the latter yeast’s pure culture a slight increase in glycerol was observed when less oxygen was provided and in general there appeared to be no impact on acetic acid production. Furthermore, there was little or no impact on volatile production, however, more repeats might reveal different results and therefore more research is needed to confirm these results. To our knowledge, this is the first study of its kind to confirm a physical cell-cell interaction between the yeast pair S. cerevisiae and L. thermotolerans. / AFRIKAANSE OPSOMMING: Die gebruik van nie-Saccharomyces gis saam met die gis S. cerevisiae in multi-inokuleringskulture het die afgelope paar jaar as n goeie hulpmiddel na vore gekom om wyn aroma te moduleer en/of om die konsentrasie van ongewensde verbindings te verminder. Sodra inokulasie plaasgevind het, het hierdie gis die potensiaal om op verskeie maniere teenoor mekaar te reageer. Kompetisie vir nutriente en die afskeiding van toksiese verbindings in n antagonistiese verhouding is alreeds goed beskryf in die literatuur. Somige studies het, alhoewel, die bestaan van ander vorme van sellulêre of molekulêre interaksies voorgestel. Een van hierdie sluit in n fisiese sell-sell interaksie en so ver as wat ons kennis strek, het nog net een studie van tevore so ‘n interaksie bevestig tussen wyn giste. Gis interaksies word ook beïnvloed deur ander faktore, soos byvoorbeeld etanol konsentrasie. Terwyl sommige studies die rol wat opgelosde suurstof speel in die oorlewing van nie-Saccharomyces gis en hulle vermoë om te kompeteer vir spasie met S. cerevisiae alreeds beklemtoon, het min navorsing al hierop gefokus. Hierdie studie het gestreef om die voorkoms van n fisiese sell-sell en/of metaboliese interaksie tussen S. cerevisie en L. thermotolerans in gemengde kultuur fermentasies van sintetiese druiwe sap te ondersoek. Vir hierdie doeleinde was fermentasies uitgevoer met behulp van ‘n Dubbel Kompartement Bioreaktor (DKB) wat gis populasies skei deur middel van ‘n membraan en hierdie was vergelyk met gemengde kultuur fermentasies sonder die membraan in dieselfde reaktor sisteem. Verder was die impak van suurstof toevoer op gis gedrag ook geassesseer. Na afloop van gemengde kultuur fermentasies in ‘n DKB, was daar waargeneem dat die teenwoordigheid van S. cerevisiae gelei het tot ‘n betekenisvolle afname in lewensvatbaarheid in L. thermotolerans. Hierdie afname was aansienlik minder in gemengde kulture waar die gis in indirekte kontak was. Saam verskaf hierdie data bewyse vir n sell-sell asook metaboliese interaksie waardeur S. cerevisiae ‘n sterk, negatiewe invloed op die groei van L. thermotolerans gehad het. Daar was egter ook waargeneem dat L. thermotolerans tot ‘n mindere mate ‘n negatiewe impak op die groei van S. cerevisiae gehad het en dat dit gelei het tot ‘n verlaging in biomassa (toe die gis in indirekte kontak was) en ‘n verlaagde maksimum CFU/mL in vergelyking met suiwer kulture. Die data dui ook aan dat fisiese kontak kon gelei het tot ‘n verhoging in gliserol en propanol produksie, maar hierdie kort verdere ondersoek. Deur die frekwensie te verminder waardeur suurstof pulse aan die fermentasies verskaf was, was ‘n verlaging in biomassa produksie en ‘n verlenging in fermentasie tydperk waargeneem. Hierdie tendense was waargeneem in almal, behalwe die gemengde kultuur fermentasies. Die effek van suurstof puls verlaging was minder op hierdie fermentasies aangesien daar geen impak op fermentasie tydperk was nie en die verlaging in biomassa minder was. Die impak van hierdie suurstof pulse was ook groter op L. thermotolerans. ‘n Klein toename in gliserol produksie was waargeneem in laasgenoemde gis se suiwer kultuur toe minder suurstof beskikbaar was en oor die algemeen was asynsuur onveranderd. Verder was daar ‘n klein of geen impak op vlugtige verbindings nie, alhoewel, meer herhalings mag verskillende resultate lewer en daarom is meer navorsing nodig om hierde resultate te bevestig. So ver as wat ons kennis strek is hierdie die eerste studie van sy soort om ‘n fisiese sell-sell interaksie tussen die gispaar S. cerevisiae en L. thermotolerans te bevestig.

<p> The thickening and classifying characteristics of small size hydrocyclones were investigatedo Test slurries, consisting of mixed cultures of microorganisms in water. were partitioned into two fractions by hydrocyclones ranginq in size from 2 mm to 10 mm body diameter which operated at inlet pressures ranging from 80 to 200 psi and volume splits ranginq from 1.0 to 3.0. </p> <p> The classtfyino response was defined in terms of the relative magnitudes of the specific growth rate of the two fractions as determined by coincident observation of duplicate batch biological reactors each seeded with one portion of the partitioned slurry. </p> <p> The thickening response was defined by the Rietema-Tenbergen separation efficiency. </p> <p> The biokinetic aspects of this investigation are emphasized in this manuscript. </p> / Thesis / Master of Engineering (MEngr)

L’objectif principal de ce travail est l’élaboration d’un modèle plus complet du plan de la ville de Policoro à l’époque archaïque que ce soit d’un point de vue de l’espace et de la chronologie que d’un point de vue culturel, politique et économique. Pour parvenir à cet objectif a été réalisée une étude de matériaux céramiques en grande partie non-publie, provenant d’une série de fouille archéologique effectue sur la collina del Castello et dans la vallata mediana. Le travail s’articule autour de quatre parties. La première (chapitre I) discute les fonds écrits littéraires et épigraphiques sur la cité archaïque de Siris. La deuxième partie (chapitre II) est dédiée à la documentation archéologique du site et s’articule en quatre paragraphes. Le premier (II.1), est une présentation des toutes les recherches précédentes, avec une attention particulière aux études portant sur la période archaïque de la cité. Le deuxième paragraphe (II.2) analyse les résultats des fouilles sur la colonie plus antique du site. Le troisième (II.3) contient une présentation des différentes formes de céramique trouvées sur le site puis une liste des différentes argiles identifiées (II.4). La troisième partie (chapitre III) est un catalogue des matériaux trouvés, présentés par secteur de fouille. Pour finir (chapitre IV) sont présentés les conclusions et la bibliographie générale. Chaque partie est complétée par une bibliographie spécifique présentée par ordre chronologique. / The most important purpose of this work (research) intends to draw up a more articulated model of the Policoro archaic settlement, analyzed from a spatial and chronological, but also cultural, political and social point of view. To achieve the goal, ceramic materials of high archaic age and archaic age, found after digging on the Hill of the Castel and in the mid - valley, have been studied, most of which unedited. The work (research) has been divided into the following sections: The first (chapter 1) contains an examination of literary and epigraphic sources concerned to Siri’s archaic settlement and an appendice about the above mentioned reports. The second part (chapter 2) focused on the documentation of materials, is made of five paragraphs including the bibliography. The first paragraph (II.1) retraces the history of the research focusing on the reports of the town archaic period. The second (II.2) consists of a precise analysis of the settlement contexts that gave the evidences of the most ancient colony, followed by the related bibliography (II.3). The fourth paragraph (II.4) shows and defines the evidenced ceramic moulds, followed by a list of different doughs identified by the autopsic analysis of clays (II.5). The third section contains the catalogue of the exhibits, shown on their contexts (Chapter III). Finally, the fourth section, dedicated to the conclusions (chapter 4). Below, a resume in French language, that contains the salient points of the research and bibliographic shorthands.

The purpose of this study is to investigate the efficiencies of bioremediation of sandy beach contaminated by crude oil. In this study, we used two lab-scale tanks, tank-A and tank-B, to simulate a sandy beach contaminated by crude oil. In the experiments, we added the bioreagents and oleophilic fertilizers (Inipol EAP 22&#x00AE;) in order to enrich crude oil degradation of sandy beach. The crude oil was degraded by nature culture in tank-A, while the crude oil was degraded by the mixed culture of several pure strains¡]MO-1, KS-1, DS-4, PF-4, PH-2, B-1, TF and XY-2¡^. We divided the experiment into five stages in this study. In conclusion, we found that the oleophilic fertilizers could increase both of the growth rate of oil degradation bacteria and crude oil biodegradation rate. However, a part of the fertilizers might flow into the ocean due to idal current. The addition of mixed culture could help to improve the biodegradation rate of sandy beach contaminated by crude oil.

Thesis (MSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The use of non-Saccharomyces yeasts together with Saccharomyces cerevisiae in mixed starter cultures has become an accepted oenological tool to enhance the organoleptic properties of wine. Recent studies have indeed demonstrated the positive contribution that non- Saccharomyces yeasts may have on the bouquet of wine. These mixed starter cultures are characterized by high inoculation levels of individual strains into the must, and each strain in turn is characterized by its own specific metabolic activity. These factors lead to a multitude of interactions occurring between the individual populations within the must. The fundamental mechanisms which drive these interactions are still largely unknown, but several studies have been conducted in order to investigate the metabolic outcome of these interactions. In this study, we endeavour to further characterize the interactions which occur between four individual non-Saccharomyces yeast strains in mixed culture fermentation with S. cerevisiae. Metschnikowia pulcherrima IWBT Y1337, Lachancea thermotolerans IWBT Y1240, Issatchenkia orientalis Y1161 and Torulaspora delbrueckii CRBO LO544 were used in mixed culture fermentations with a commercial strain of S. cerevisiae at an inoculation ratio of 10:1 (non-Saccharomyces: S. cerevisiae). The biomass evolution and fermentation kinetics of both participating species were affected by the high cell density of the other, with neither population reaching the maximal density attained by the pure culture fermentation. The final wine composition of each individual mixed fermentation showed clear differences, from the pure cultured S. cerevisiae and from each other, based on the concentrations of the major volatile compounds found in the wine. Upon further characterization of these specific mixed culture fermentations, it was found that each individual combination of non-Saccharomyces and S. cerevisiae produced similar increases and decreases of certain major volatile compounds as demonstrated by previous authors, using the same combination of non-Saccharomyces species together with S. cerevisiae. From a winemaking perspective, the use of these non- Saccharomyces yeast strains in combination with S. cerevisiae could be a useful strategy to diversify the chemical composition of wine, by increasing the concentration of certain desirable volatile compounds and by modulating the concentration of undesirable metabolites. Furthermore, this research serves as a foundation for further elucidation of the interactions which drive these metabolic outcomes in response to the high cell density of two yeast populations in mixed culture fermentations.

abstract: On average, our society generates ~0.5 ton of municipal solid waste per person annually. Biomass waste can be gasified to generate synthesis gas (syngas), a gas mixture consisting predominantly of CO, CO2, and H2. Syngas, rich in carbon and electrons, can fuel the metabolism of carboxidotrophs, anaerobic microorganisms that metabolize CO (a toxic pollutant) and produce biofuels (H2, ethanol) and commodity chemicals (acetate and other fatty acids). Despite the attempts for commercialization of syngas fermentation by several companies, the metabolic processes involved in CO and syngas metabolism are not well understood. This dissertation aims to contribute to the understanding of CO and syngas fermentation by uncovering key microorganisms and understanding their metabolism. For this, microbiology and molecular biology techniques were combined with analytical chemistry analyses and deep sequencing techniques. First, environments where CO is commonly detected, including the seafloor, volcanic sand, and sewage sludge, were explored to identify potential carboxidotrophs. Since carboxidotrophs from sludge consumed CO 1000 faster than those in nature, mesophilic sludge was used as inoculum to enrich for CO- and syngas- metabolizing microbes. Two carboxidotrophs were isolated from this culture: an acetate/ethanol-producer 99% phylogenetically similar to Acetobacterium wieringae and a novel H2-producer, Pleomorphomonas carboxidotrophicus sp. nov. Comparison of CO and syngas fermentation by the CO-enriched culture and the isolates suggested mixed-culture syngas fermentation as a better alternative to ferment CO-rich gases. Advantages of mixed cultures included complete consumption of H2 and CO2 (along with CO), flexibility under different syngas compositions, functional redundancy (for acetate production) and high ethanol production after providing a continuous supply of electrons. Lastly, dilute ethanol solutions, typical of syngas fermentation processes, were upgraded to medium-chain fatty acids (MCFA), biofuel precursors, through the continuous addition of CO. In these bioreactors, methanogens were inhibited and Peptostreptococcaceae and Lachnospiraceae spp. most likely partnered with carboxidotrophs for MCFA production. These results reveal novel microorganisms capable of effectively consuming an atmospheric pollutant, shed light on the interplay between syngas components, microbial communities, and metabolites produced, and support mixed-culture syngas fermentation for the production of a wide variety of biofuels and commodity chemicals. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2017

Submitted by (edna.saturno@ufrpe.br) on 2016-06-17T15:46:02Z No. of bitstreams: 1 Helton Soriano Bezerra de Oliveira.pdf: 608876 bytes, checksum: b11ad3adcdbf097206eeabe19459bed4 (MD5) / Made available in DSpace on 2016-06-17T15:46:02Z (GMT). No. of bitstreams: 1 Helton Soriano Bezerra de Oliveira.pdf: 608876 bytes, checksum: b11ad3adcdbf097206eeabe19459bed4 (MD5) Previous issue date: 2012-06-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Some laboratory studies had shown that microcystins exert allelopathic effects on organisms of the aquatic biota. However, the experimental designs rarely test concentrations found in natural environments (above 10 μg.L-1), which makes uncertain the action of microcystins as allelopathic compounds. Our study aimed to evaluate the effects of microcystins in concentrations usually found in natural conditions on the growth of strains of green microalgae (Monoraphidium convolutum and Scenedesmus acuminatus). For this purpose mixed cultures containing cyanobacteria and green algae were analyzed. Cultures of microalgae with the addition of crude extracts of cyanobacteria microcystin-producing and non-microcystin-producing were also performed. Two non-clonal axenic strains of cyanobacteria were used: Microcystis aeruginosa (microcystin-producing – MC+) and Microcystis panniformis (non-producer-producing – MC-). The experiments were conducted under controlled laboratory conditions (Erlenmeyers with a capacity of 1000 mL, with 600 mL of final volume of culture in BG11 medium at pH 7.4, temperature 24 ± 1 ° C, photoperiod 14h: 10h (light:dark), 40 μmol.m-2.s-1 light intensity). It was observed that in mixed cultures, both green microalgae and cyanobacteria had their growth reduced, which was observed when analyzing variations in specific growth rate. The microcystin production by M. aeruginosa (MC +) increased when it was in cultured together with M. convolutum. However when cultured with S. acuminatus the production did not change. The growth of green microalgae has not changed in treatments with addition of crude cell extracts of M. aeruginosa (MC +) containing 5μg.L-1 and 10μg.L-1 of total microcystins. Similarly, for the treatments with addition of crude cell extracts of M. panniformis (MC-) the growth of these green microalgae did not change. Our results do not support of the allelopathic function of microcystins, at least in the growth of these green microalgae. / Alguns estudos em laboratório mostram que as microcistinas exercem efeitos alelopáticos sobre organismos da biota aquática. No entanto, os desenhos experimentais testam concentrações dificilmente encontradas nos ambientes naturais (acima 10 μg.L-1), o que torna imprecisa a afirmação das microcistinas atuarem como compostos alelopáticos. Nosso estudo teve por objetivo avaliar os efeitos das microcistinas, em concentrações usualmente encontradas em condições naturais, sobre o crescimento de linhagens de microalgas verdes (Monoraphidium convolutum e Scenedesmus acuminatus). Para tanto foram realizados cultivos mistos, entre cianobactérias e microalgas verdes e cultivos dessas microalgas verdes com adição de extratos brutos de cianobactérias produtoras e não-produtoras de microcistinas. Foram utilizadas duas linhagens clonais não-axênicas de cianobactérias: Microcystis aeruginosa (produtora de microcistinas – MC+) e Microcystis panniformis (não-produtora – MC-). Os experimentos foram desenvolvidos sob condições controladas em laboratório (erlenmeyers com capacidade 1000 mL, com 600 mL de volume final de cultura, em meio BG11, pH 7,4 temperatura 24 ± 1°C, 14h:10h fotoperíodo (claro:escura), 40μmol.m-2.s-1 de intensidade luminosa). Foi observado que em cultivos mistos, tanto as microalgas verdes quanto as cianobactérias apresentam redução de crescimento atribuída a alterações na taxa de crescimento específico. M. aeruginosa (MC+) teve a produção de microcistinas elevada no cultivo com M. convolutum, no entanto, com S. acuminatus a produção não foi alterada. O crescimento das microalgas verdes não foi alterado nos tratamentos com adição de extrato brutos de células de M. aeruginosa (MC+) contendo 5μg.L-1 e 10μg.L-1 de microcistinas totais. Igualmente, para os tratamentos com extratos de M. panniformis (MC-) o crescimento dessas microalgas verdes não foi alterado. Os nossos resultados não suportam a função alelopática das microcistinas, pelo menos sobre o crescimento dessas microalgas verdes.

No description available.

The development of anaerobic digestion processes has gained recognition for its potential for producing volatile fatty acids alongside bio-alcohols. In addition, the fermentation process and the products produced from biological fermentation have the possibility to overcome the abundance of organic waste in our society, which is potentially immensely rich in untapped valuable potential products. The current project aims at producing medium chained volatile fatty acids and alcohols from short-chain volatile fatty acids using hydrogen as an electron donor. For efficient conversion, inhibition of methanogenic microorganisms was performed by thermally pre-treating the microorganisms at 90 °C for 15 min. The highest observed concentrations of volatile fatty acid were 6.42 ± 0.09 g/L and the concentration of ethanol was 0.33±0.03 g/L. These concentrations were obtained with the addition of 4 g/L of liquid substrate and gas co-substrate (H2:CO2). Moreover, the predominant product from the present experiment was valeric acid and it reached its highest concentration of 1.41 g/L after 37 days. Interestingly, the addition of H2:CO2 co-substrate showed that this fermentation can be used for carbon capture and utilisation alongside hydrogen consumption in a ratio of 1:1 to increase the value of short-chain fatty acids. Furthermore, this can contribute to decreased CO2 emissions and reduced use of fossil resources for alcohol production which is in line with the global environmental goals.