A pinta preta provocada pelo fungo Guignardia psidii Ullasa e Rawal (Phyllosticta psidiicola (Petrak) van der Aa) vem gerando perdas pós-colheita na produção de goiaba para consumo in natura. Este trabalho buscou maiores informações sobre esta doença por meio do estudo do efeito da temperatura, da duração do período de molhamento, do efeito dos gases dióxido de carbono e etileno, e da idade dos frutos de goiabeira na pré-penetração de conídios de G. psidii. Os estudos in vitro foram avaliados por meio de microscópio de luz e os in vivo por meio de microscópio eletrônico de varredura, registrando-se a porcentagem de conídios germinados, apressórios formados e apressórios melanizados (in vitro). O efeito da temperatura (10 a 40ºC) e da duração do período de molhamento (6 a 48 in vitro e 6 a 24 horas in vivo) na germinação, formação de apressórios e apressórios melanizados (in vitro) foram avaliados em superfície de poliestireno e de frutos de goiabeira. Em ambas as superfícies, à medida que a temperatura aumentou, observou-se o aumento gradual da germinação, formação de apressório e apressório melanizado atingindo o máximo a 25ºC e duração de período de molhamento de 24 horas in vivo e 48 horas in vitro. Nessas condições, os valores obtidos foram 38% de conídios germinados, 37,7% de apressórios formados e 32,7% de apressórios melanizados in vitro e 45,6% de conídios germinados e 11,2% de apressórios formados in vivo. As taxas de germinação e formação de apressório foram maiores no experimento in vivo. A germinação e formação de apressório de conídios de G. psidii foram avaliadas em cinco diferentes idades de frutos: 10 dias, 35 dias, 60 dias, 85 dias e 110 dias. Observou-se o aumento gradual das variáveis avaliadas com o aumento da idade do fruto, apresentando, em frutos com 10 dias, 8,4% de conídios germinados e 3,2% de apressórios formados, enquanto os frutos com 110 dias apresentaram 43,2% de conídios germinados e 26,4% de apressórios formados. O efeito das concentrações 0, 3, 6 e 12% de dióxido de carbono e 0, 1, 3 e 6 ppm de etileno na pré-penetração de conídios de G. psidii foram avaliadas in vitro e in vivo. No experimento in vitro, o aumento das concentrações de dióxido de carbono provocou queda na germinação dos conídios de G. psidii quando comparado ao controle. No entanto, entre as concentrações deste gás a taxa de germinação manteve-se estável. Portanto, no controle esta variável apresentou valor médio de 45,1% enquanto que nas concentrações 3, 6 e 12% do gás passou para, respectivamente, 24,6%, 22,6% e 25,8%. Entretanto, o aumento das concentrações deste gás provocou decréscimo progressivo da taxa de formação de apressórios e apressórios melanizados. Na concentração de 3% de dióxido de carbono houve 10,3% de apressórios formados e 5,4% de apressórios melanizados e na concentração de 12%, esses valores foram reduzidos para 4,1% e 0,5%, respectivamente. No entanto, no experimento in vivo, as taxas de germinação e formação de apressórios apresentaram redução gradativa entre as concentrações 3 e 6% de dióxido de carbono, elevando-se novamente a 12%, passando de 28,2% de conídios germinados e 20,5% de apressórios formados na concentração de 6% de dióxido de carbono para, respectivamente, 49,3% e 38,2% a 12% de concentração desse gás. Esse comportamento pode ser explicado devido à remoção dos conídios não germinados durante o preparo das amostras para visualização em microscópio eletrônico. O etileno, tanto nos experimento in vitro quanto in vivo não apresentou efeito sobre a germinação e formação de apressórios de G. psidii. Apresentando no controle in vitro 34,6% de conídios 9 germinados, 34,2% de apressórios formados e 29,9% de apressórios melanizados e na maior concentração de etileno estudada (6 ppm) 26,7% de conídios germinados, 26,3% de apressórios formados e 20,2% de apressórios melanizados. Nos ensaios in vivo, o controle apresentou 40% de conídios germinados e 32,7% de apressórios formados e na maior concentração de etileno estudada 49,3% de conídios germinados e 38,2% de apressórios formados. / The black spot caused by the fungus Guignardia psidii Ullasa and Rawal (Phyllosticta psidiicola (Petrak) van der Aa) has been causing post-harvest losses of guava fruit for consumption in natura. This work was designed to investigate the effects of temperature, wetness duration, carbon dioxide and ethylene concentration, and guava fruit age on the pre-penetration of G. psidii. The percentages of germinated conidia, formed appressoria and melanized appressoria were evaluated in both in vitro and in vivo experiments, using a light microscope in the former and a scanning electron microscope in the later. The effects of temperature (10 to 40ºC) and wetness duration (6 to 48 hours in vitro and 6 to 24 hours in vivo) on the germination, appressoria formation and melanized appressoria (in vitro) were evaluated on a polystyrene surface and on the fruit\'s surface. In both surfaces, as the temperature increased a gradual increase in conidia germination, appressoria formation and melanized appressoria was observed, reaching maximum at 25ºC with wetness duration being 24 hours in vivo and 48 hours in vitro. In these conditions, the values obtained were 38.0% germinated conidia, 37.7% formed appressoria and 32.7% melanized appressoria in vitro and 45.6% germinated conidia and 11.2% formed appressoria in vivo. Conidia germination and appressoria formation rates were higher in the in vivo experiment. G. psidii conidia germination and appressoria formation were evaluated at five different fruit ages: 10 days, 35 days, 60 days, 85 days and 110 days. A gradual increase of the evaluated variables was observed as the fruit\'s age increased, presenting in fruits with 10 days, 8.4% germinated conidia and 3.2% formed appressoria, while the fruits with 110 days presented 43.2% germinated conidia and 26.4% formed appressoria. The effects of carbon dioxide concentration at 0, 3, 6 and 12% and ethylene at 0, 1, 3 and 6 ppm on the pre-penetration of G. psidii were evaluated in vitro and in vivo. In the in vitro experiment an increase in the carbon dioxide concentration provoked a decrease in G. psidii conidia germination when compared to the control. However, between the gas concentrations tested, the germination rate was stable. Therefore, in the control this variable presented a mean value of 45.1% while in the gas concentration of 3, 6 and 12%, the mean values were, respectively, 24.6%, 22.6% and 25.8%. However, increasing carbon dioxide concentration caused a progressive decrease in appressoria formation and melanized appressoria rates. At a concentration of 3% carbon dioxide, there was 10.3% formed appressoria and 5.4% melanized appressoria and at 12% concentration these values were reduced to 4.1% and 0.5%, respectively. Nonetheless, in the in vivo experiment, the rates of germination and appressorium formation presented a gradual reduction between the 3 and 6% dioxide carbon concentrations, increasing again at 12%, increasing from 28.2% germinated conidia and 20.5% formed appressoria at 6% carbon dioxide concentration to, respectively, 49.3% and 38.2% at 12% concentration of this gas. This behavior could be due to the removal of the conidia that did not germinate, during the preparation of the sample for electron microscope observation. Ethylene, in both the in vitro and in the in vivo experiments, showed no effect on G. psidii germination and appressoria formation, presenting in the in vitro control, 34.6% germinated conidia, 34.2% formed appressoria and 29.9% melanized appressoria and in the highest ethylene concentration studied (6 ppm) 26.7% germinated conidia, 26.3% formed appressoria and 20.2% melanized appressoria. In the in vivo assays, the control presented 40.0% 11 germinated conidia and 32.7% formed appressoria and in the highest ethylene concentration studied 49.3% germinated conidia and 38.2% formed appressoria.

Abstract Biodegradation is an aerobic or anaerobic degradation reaction where bacteria use organic materials as an energy source. In the aerobic biodegradation reaction, bacteria need oxygen as an electron acceptor, whereas an anaerobic reaction takes place in the absence of oxygen. Compounds degrade totally or partially, and produce simple inorganic species, such as CO2, CH4, NH3, NO3−, and H2O, as well as by-products that may be non-biodegradable and/or toxic. In this thesis, the biodegradability of recycled vegetable oils, surface-active agents, and condensing waters from the process of wood drying were studied using the manometric respirometric BOD OxiTop method. The biodegradation of organic compounds was measured under the standard conditions (OECD 301F), and also in other matrices, such as different waters and soils. These are very different environments with respect to the biodegradation reaction in nature. The main differences in waters and soils are their organic and inorganic nutrient contents, bacteria strains, and temperatures. The BOD OxiTop method is based on automatic pressure detection in a closed reactor vessel. Oxygen is consumed and carbon dioxide is formed in the aerobic reaction. The pressure decrease is detected after the carbon dioxide is adsorbed into a NaOH pellet or solution. The pressure change is dependent on oxygen consumption. The degree of biodegradation is calculated from the BOD value of the sample. The studied recycled vegetable oils were found to be 60–83% biodegradable, and the added surface-active agent did not affect their biodegradation. Biodegradation of tall oil soaps was also examined in sand, topsoil, groundwater, and surface water, as well as under OECD 301F standard conditions. Tall oil soaps were proven to be 50–85% biodegradable. Concrete solvent agent (CSA) was also proven to be 78–83% biodegradable under standard conditions. Another detergent, cetyltrimethylammonium bromide (CTAB), was found to be toxic, whereas Triton X-100 biodegraded by only 6% in solution. Biodegradation of the soil matrix was found to be enhanced with added surface-active agents. This can be explained by better wetting of small pores with surface-active agents, as compared to the behavior of pure water. The biodegradation of the matrix occurred even with toxic surface-active agents. Organic pollutants of wastewaters from the process of wood drying were 25–61% biodegradable during a 28-day period, and were proven to be quite pure when considering the carbon content of the samples. Based on these results, the disposal into drainage of condensing waters from wood drying may be regarded as safe, which from an economical viewpoint is a very important conclusion. / Tiivistelmä Biohajoavuus on luonnollinen aerobinen tai anaerobinen hajoamisprosessi, jossa bakteerit käyttävät orgaanista materiaalia energian lähteenä. Aerobisessa reaktiossa bakteerit tarvitsevat happea elektronien vastaanottajaksi, kun taas anaerobinen reaktio tapahtuu hapettomissa olosuhteissa. Yhdisteet hajoavat joko täysin tai osittain sekä tuottavat yksinkertaisia epäorgaanisia yhdisteitä, kuten CO2, CH4, NH3, NO3− tai H2O. Reaktiossa voi myös muodostua sivutuotteita, jotka voivat olla biohajoamattomia ja/tai toksisia. Tässä työssä on tutkittu kierrätettyjen kasviöljyjen, pinta-aktiivisten aineiden sekä jätevesien sisältämien orgaanisen aineksien biohajoavuuksia käyttäen manometristä respirometristä BOD OxiTop-menetelmää. Biohajoavuutta mitattiin standardiolosuhteiden (OECD 301F) lisäksi muissakin olosuhteissa, kuten erilaisissa maissa ja vesissä. Nämä ovat kaikki hyvin erilaisia ympäristöjä luonnossa tapahtuville biohajoavuusreaktioille. Pääasialliset erot ovat sekä orgaanisten että epäorgaanisten ravinteiden määrässä, bakteerikannoissa ja lämpötilassa. BOD OxiTop-menetelmä perustuu automaattiseen paineen muutoksen havainnointiin suljetussa astiassa. Aerobisessa reaktiossa kuluu happea ja muodostuu hiilidioksidia, joka imeytetään NaOH-pelletteihin tai -liuokseen ja tästä muodostuu alipaine. Paineen muutokset muunnetaan hapenkulutuksen arvoiksi, joista lasketaan biohajoavuusaste. Tutkittujen kierrätettyjen kasviöljyjen biohajoavuusasteet vaihtelivat välillä 60–83 %, eikä lisätty pinta-aktiivinen aine vaikuttanut kyseisten ekoöljyjen biohajoavuuteen. Mäntysaippuoiden biohajoavuus tutkittiin standardiolosuhteiden lisäksi hiekassa, mullassa, pohjavedessä sekä pintavedessä. Niiden biohajoavuusasteet vaihtelivat välillä 50–85 %. Betoninpesuaineen biohajoavuusaste standardiolosuhteissa oli 78–83 %. Kahdesta tutkituista pinta-aktiivisista aineista setrimoniumbromidi (CTAB) oli myrkyllinen liuosolosuhteissa eikä täten biohajonnut ja Triton X-100 biohajosi vain 6 %. Pinta-aktiivisen aineen lisääminen maahan aiheutti matriisina käytetyn maan biohajoamisen. Tämä voitiin selittää siten, että pintajännityksen laskemisen jälkeen neste voi paremmin tunkeutua maan pieniin huokosiin ja näin tuoda hajoamatonta orgaanista ainesta ja uusia bakteereita biohajoavuuskäyttöön. Tämä ilmiö havaittiin myös myrkyllisen pinta-aktiivisen aineen lisäyksen jälkeen. Jätevesien sisältämät orgaaniset ainekset hajosivat 25–61 % 28 päivän aikana ja niiden havaittiin olevan hiilen määrän huomioon ottaen hyvin puhtaita. Tässä tutkimuksessa saatujen tulosten perusteella tutkitut puunkuivauksen kondenssivedet voidaan laskea viemäriin, mikä on erittäin tärkeä tulos ekologiselta ja taloudelliselta kannalta katsottuna.

Abstract Oily wastewaters are heterogeneous, containing various types of oils, surfactants from detergents, metals etc. Oily wastewaters are produced from a wide range of industries such as metalworking, petroleum refineries, the petrochemical industry, transportation as well as the textile and food industries. Oily wastewaters, especially those containing stable oil-in-water emulsions, require advanced treatment as conventional treatment methods have their limitations to meet ever-stricter environmental regulations. Ultrafiltration is a widely accepted and commonly used treatment method for oily wastewaters. The first aim of this thesis was to increase knowledge concerning the performance of an industrial-scaled ultrafiltration-based process treating concentrated real oily wastewaters. The demand for a more effective pre-treatment method for ultrafiltration to enhance performance and decrease fouling of membrane was observed. The second aim of the thesis was to investigate the suitability and efficiency of different methods for treating concentrated model oil-in-water emulsions and real oily wastewaters. The treatment methods studied were electrocoagulation (electrolytic dissolution of anodic metal), conventional coagulation-flocculation followed by either sedimentation or dissolved air flotation, and dissolved air flotation utilising cationic air bubbles. Electrocoagulation was discovered to be a promising treatment method for various types of oil-in-water emulsions. Dissolved air flotation with cationic modified air bubbles was proven to be an efficient method with even higher treatment results with smaller chemical doses when compared to conventional coagulation-flocculation followed by dissolved air flotation. The biodegradation of various components is an important measure of their impact on the environment in case of spillage. The third aim of the thesis was to explore the biodegradability of different types of oils and surfactants in solution conditions and soils. It was discovered that the biodegradation of light fuel oil continued during a three-month time period, reaching a biodegradation degree of over 60% in mineral-rich soil. For surfactants, their distinct effect on the biodegradation of organic material in soil was observed, and it masked the biodegradation of the surfactants themselves. / Tiivistelmä Öljyiset jätevedet ovat heterogeenisiä, sisältäen mm. erityyppisiä öljyjä, metalleja ja pesuaineiden pinta-aktiivisia aineita. Öljyisiä jätevesiä muodostuu laajalti eri teollisuuksista, kuten metallintyöstöstä, öljyn jalostuksesta, petrokemian teollisuudesta, ruoka- ja tekstiiliteollisuudesta sekä liikenteestä. Öljyiset jätevedet, varsinkin stabiileja öljyemulsioita sisältävät, vaativat tehokkaan käsittelymenetelmän, jotta ympäristölainsäädännön ja luvituksen ehdot täyttyvät. Ultrasuodatus on yleisesti käytössä oleva öljyisten jätevesien käsittelymenetelmä. Tämän väitöstyön ensimmäinen tavoite oli lisätä tietoutta teollisen mittakaavan konsentroituneiden öljyisten jätevesien ultrasuodatusprosessien tehokkuudesta. Prosessien strategisista kohdista kerättyjen öljyisten jätevesien karakterisointitulosten perusteella havaittiin, että ennen ultrasuodatusta tarvitaan tehokas esikäsittelyvaihe prosessin tehostamiseksi ja ultrasuodattimen tukkeutumisen vähentämiseksi. Täten toinen väitöstyön tavoite oli selvittää eri menetelmien soveltuvuutta ja tehokkuutta konsentroituneiden malliaineina käytettyjen öljyemulsioiden ja öljyisten jätevesien käsittelyssä. Tutkitut käsittelymenetelmät olivat elektrokoagulaatio (sähkökemiallinen flokkaavien metalli-ionien liuottaminen anodilta), koagulaatio-flokkulaatio ja laskeutus/korkeapaineflotaatio sekä korkeapaineflotaatiomenetelmä, joka hyödyntää kationisia ilmakuplia. Elektrokoagulaation todettiin olevan erittäin tehokas käsittelymenetelmä, jolla saavutettiin korkeat puhdistustulokset erityyppisille öljyemulsioille. Korkeapaineflotaatiolla, joka hyödyntää kationisia ilmakuplia, saavutettiin hyvät puhdistustulokset jopa pienemmillä kemikaalimäärillä verrattuna perinteiseen koagulaatio-flokkulaatioon ja korkepaineflotaation. Erilaisten komponenttien biohajoavuus on tärkeä suure arvioitaessa niiden ympäristövaikutuksia. Väitöstyön kolmas tavoite oli selvittää erilaisten öljyjen ja pinta-aktiivisten aineiden biohajoavuutta erilaisissa liuosolosuhteissa ja maa-aineksissa. Tärkeimmät biohajoavuustutkimustulokset olivat, että kevyt polttoöljy saavutti kolmen kuukauden mittauksen aikana yli 60 % biohajoavuusasteen mineraalirikkaassa maa-aineksessa. Pinta-aktiivisten aineiden havaittiin lisäävän huomattavasti maan orgaanisen aineksen biohajoamista, ja tämä vaikeutti itse pinta-aktiivisten aineiden biohajoamisen arviointia.

A pinta preta dos citros tem como agente causal o fungo G. citricarpa. A doença causa depreciação estética dos frutos e praticamente inviabiliza a exportação de laranja in natura principalmente para a União Européia, por ser considerada uma doença quarentenária. Frutos colhidos contendo infecções quiescentes, embora sem sintomas, podem desenvolvê-los durante o processo de exportação. A utilização de fungicidas é o principal método de controle utilizado em pré e pós-colheita. No entanto, o custo do controle químico é significativamente alto e já foi relatado o surgimento de isolados resistentes. A levedura S. cerevisiae é capaz de inibir o desenvolvimento in vitro de G. citricarpa e o antagonismo se deve a produção de compostos orgânicos voláteis de ação fungistática. Em virtude da procura por novos métodos de controle menos danosos à saúde humana e meio ambiente, dos prejuízos causados pela doença e do potencial dos compostos voláteis no controle da doença na pós-colheita, o trabalho visou identificar os compostos voláteis produzidos pela levedura e elucidar os mecanismos envolvidos na inibição do fitopatógeno. Esse conhecimento é fundamental para o desenvolvimento de técnicas inovativas de controle. A produção de compostos voláteis antimicrobianos por S. cerevisiae foi dependente do substrato utilizado para o seu cultivo, sendo a glicose, sacarose e maltose fontes de carbono favoráveis. Foi verificado através da análise em SPME-GC-MS que a levedura produziu em meio BDA, principalmente compostos pertencentes ao grupo dos álcoois, constituindo 95% da composição total, além de ésteres em menor proporção. A mistura artificial de voláteis mimetizou os efeitos dos voláteis produzidos pela levedura, sendo os valores de MIC50 e MIC100 de 0,48 µL mL-1 e 2,84 µL mL-1, respectivamente. A exposição do fitopatógeno aos compostos voláteis reduziu a síntese de proteínas e inibiu a atividade de enzimas associadas à morfogênese (quitinase, b-1,3-glucanase, lacase e tirosinase). Os compostos voláteis desencadearam o processo de estresse oxidativo no fungo, fato observado através da elevação da atividade de enzimas (superóxido dismutase e catalase) associadas a mecanismos de detoxificação de espécies ativas de oxigênio. A análise das proteínas diferencialmente expressas de G. citricarpa, através de eletroforese bidimensional, indicou que os compostos voláteis alteraram a expressão de 40 proteínas, sendo 29 inibidas e 11 superexpressas. A mistura artificial de voláteis também foi ativa contra fungos de diversos grupos taxonômicos, no entanto, não apresentou atividade sobre as bactérias testadas. Os compostos 3-metil-1-butanol e 2- metil-1-butanol foram os mais ativos quando utilizados isoladamente contra Colletotrichum gloesporioides, Penicillium digitatum, Sclerotinia sclerotiorum e Fusarium oxysporum. Sementes de feijão fumigadas com a mistura artificial de voláteis exibiram redução na incidência de S. sclerotiorum. A mistura também exibiu efeito nematicida sobre Meloidogyne javanica. Portanto, os resultados demonstram que os voláteis identificados em S. cerevisiae afetam a síntese de proteínas e a atividade de enzimas associadas ao crescimento vegetativo de G. citricarpa. Finalmente, fumigação utilizando compostos voláteis apresenta potencial no controle de G. citricarpa em pós-colheita, bem como de outros organismos de importância agronômica. O trabalho também contribuiu com novos elementos sobre o papel dos voláteis na interação entre microrganismos na natureza. / The citrus black spot has as causal agent the fungus G. citricarpa. The disease causes aesthetic depreciation of fruits and practically makes them unviable for exportation mainly to European Union where the disease is considered a quarantine pest. Harvested fruits can have quiescent infections although without symptoms and can develop them during the exportation process. The use of fungicides is the main chemical control method used in pre and post-harvest, however the cost is significantly high and it was already described the development of fungicide resistant strains. The yeast S. cerevisiae is able to inhibit the in vitro G. citricarpa growth, and the antagonism is due to production of volatile organic compounds (VOCs) of fungistatic effect. Because of the search for new control methods less harmful for human health and environment, the losses caused by the disease and the potential of the VOCs in the control of the pathogen in the post-harvest, the aim of this work was to identify the VOCs produced by the yeast and to elucidate the mechanisms involved in the inhibition of the fungus. This knowledge is essential for the development of innovative control techniques. The results showed that the production of antimicrobial VOCs by S. cerevisiae was dependent on the substrate used, being glucose, sucrose and maltose favorable carbon sources. It was verified through analysis in SPME-GC-MS that the yeast, grown on PDA medium, produced mainly compounds belonging to the group of alcohols (95% of the total composition), besides esters in smaller proportion. An artificial volatile mixture reproduced the effects of the VOCs produced by the yeast, being the values of MIC50 and MIC100 of 0.48 µL mL-1 and 2.84 µL mL-1, respectively. The phytopathogen exposition to the VOCs reduced protein synthesis and inhibited the activity of morphogenesis associated enzymes like chitinase, b-1,3-glucanase, laccase and tyrosinase. The VOCs initiated the oxidative stress process, which was observed through the increase in the activity of superoxide dismutase and catalase, enzymes associated to the detoxification of active oxygen species. The analysis of the differentially expressed proteins of G. citricarpa, through two-dimensional gel electrophoresis, indicated that the VOCs modified the expression of 40 proteins, being 29 down regulated and 11 up regulated. The artificial mixture of VOCs was also active against fungi of several taxonomic groups, however, there were no activity against bacteria. The compounds 3-methyl-1-butanol and 2-methyl-1-butanol were the most active when tested alone against Colletotrichum gloesporioides, Penicillium digitatum, Sclerotinia sclerotiorum and Fusarium oxysporum. Bean seeds fumigated with the artificial mixture of VOCs showed reduction in S. sclerotiorum incidence. In addition, the VOCs exhibited nematicidal effect against Meloidogyne javanica. The results demonstrate that the VOCs produced by S. cerevisiae affect protein synthesis and the activity of enzymes associated to the vegetative growth in G. citricarpa. Thus, the fumigation using VOCs presents potential in the control of citrus black spot disease in post-harvest as well as of other organisms of agronomic importance. The present workalso contributed with new information regarding the role of the VOCs in the interactions among microorganisms in nature.

A pinta preta dos citros tem como agente causal o fungo G. citricarpa. A doença causa depreciação estética dos frutos e praticamente inviabiliza a exportação de laranja in natura principalmente para a União Européia, por ser considerada uma doença quarentenária. Frutos colhidos contendo infecções quiescentes, embora sem sintomas, podem desenvolvê-los durante o processo de exportação. A utilização de fungicidas é o principal método de controle utilizado em pré e pós-colheita. No entanto, o custo do controle químico é significativamente alto e já foi relatado o surgimento de isolados resistentes. A levedura S. cerevisiae é capaz de inibir o desenvolvimento in vitro de G. citricarpa e o antagonismo se deve a produção de compostos orgânicos voláteis de ação fungistática. Em virtude da procura por novos métodos de controle menos danosos à saúde humana e meio ambiente, dos prejuízos causados pela doença e do potencial dos compostos voláteis no controle da doença na pós-colheita, o trabalho visou identificar os compostos voláteis produzidos pela levedura e elucidar os mecanismos envolvidos na inibição do fitopatógeno. Esse conhecimento é fundamental para o desenvolvimento de técnicas inovativas de controle. A produção de compostos voláteis antimicrobianos por S. cerevisiae foi dependente do substrato utilizado para o seu cultivo, sendo a glicose, sacarose e maltose fontes de carbono favoráveis. Foi verificado através da análise em SPME-GC-MS que a levedura produziu em meio BDA, principalmente compostos pertencentes ao grupo dos álcoois, constituindo 95% da composição total, além de ésteres em menor proporção. A mistura artificial de voláteis mimetizou os efeitos dos voláteis produzidos pela levedura, sendo os valores de MIC50 e MIC100 de 0,48 µL mL-1 e 2,84 µL mL-1, respectivamente. A exposição do fitopatógeno aos compostos voláteis reduziu a síntese de proteínas e inibiu a atividade de enzimas associadas à morfogênese (quitinase, b-1,3-glucanase, lacase e tirosinase). Os compostos voláteis desencadearam o processo de estresse oxidativo no fungo, fato observado através da elevação da atividade de enzimas (superóxido dismutase e catalase) associadas a mecanismos de detoxificação de espécies ativas de oxigênio. A análise das proteínas diferencialmente expressas de G. citricarpa, através de eletroforese bidimensional, indicou que os compostos voláteis alteraram a expressão de 40 proteínas, sendo 29 inibidas e 11 superexpressas. A mistura artificial de voláteis também foi ativa contra fungos de diversos grupos taxonômicos, no entanto, não apresentou atividade sobre as bactérias testadas. Os compostos 3-metil-1-butanol e 2- metil-1-butanol foram os mais ativos quando utilizados isoladamente contra Colletotrichum gloesporioides, Penicillium digitatum, Sclerotinia sclerotiorum e Fusarium oxysporum. Sementes de feijão fumigadas com a mistura artificial de voláteis exibiram redução na incidência de S. sclerotiorum. A mistura também exibiu efeito nematicida sobre Meloidogyne javanica. Portanto, os resultados demonstram que os voláteis identificados em S. cerevisiae afetam a síntese de proteínas e a atividade de enzimas associadas ao crescimento vegetativo de G. citricarpa. Finalmente, fumigação utilizando compostos voláteis apresenta potencial no controle de G. citricarpa em pós-colheita, bem como de outros organismos de importância agronômica. O trabalho também contribuiu com novos elementos sobre o papel dos voláteis na interação entre microrganismos na natureza. / The citrus black spot has as causal agent the fungus G. citricarpa. The disease causes aesthetic depreciation of fruits and practically makes them unviable for exportation mainly to European Union where the disease is considered a quarantine pest. Harvested fruits can have quiescent infections although without symptoms and can develop them during the exportation process. The use of fungicides is the main chemical control method used in pre and post-harvest, however the cost is significantly high and it was already described the development of fungicide resistant strains. The yeast S. cerevisiae is able to inhibit the in vitro G. citricarpa growth, and the antagonism is due to production of volatile organic compounds (VOCs) of fungistatic effect. Because of the search for new control methods less harmful for human health and environment, the losses caused by the disease and the potential of the VOCs in the control of the pathogen in the post-harvest, the aim of this work was to identify the VOCs produced by the yeast and to elucidate the mechanisms involved in the inhibition of the fungus. This knowledge is essential for the development of innovative control techniques. The results showed that the production of antimicrobial VOCs by S. cerevisiae was dependent on the substrate used, being glucose, sucrose and maltose favorable carbon sources. It was verified through analysis in SPME-GC-MS that the yeast, grown on PDA medium, produced mainly compounds belonging to the group of alcohols (95% of the total composition), besides esters in smaller proportion. An artificial volatile mixture reproduced the effects of the VOCs produced by the yeast, being the values of MIC50 and MIC100 of 0.48 µL mL-1 and 2.84 µL mL-1, respectively. The phytopathogen exposition to the VOCs reduced protein synthesis and inhibited the activity of morphogenesis associated enzymes like chitinase, b-1,3-glucanase, laccase and tyrosinase. The VOCs initiated the oxidative stress process, which was observed through the increase in the activity of superoxide dismutase and catalase, enzymes associated to the detoxification of active oxygen species. The analysis of the differentially expressed proteins of G. citricarpa, through two-dimensional gel electrophoresis, indicated that the VOCs modified the expression of 40 proteins, being 29 down regulated and 11 up regulated. The artificial mixture of VOCs was also active against fungi of several taxonomic groups, however, there were no activity against bacteria. The compounds 3-methyl-1-butanol and 2-methyl-1-butanol were the most active when tested alone against Colletotrichum gloesporioides, Penicillium digitatum, Sclerotinia sclerotiorum and Fusarium oxysporum. Bean seeds fumigated with the artificial mixture of VOCs showed reduction in S. sclerotiorum incidence. In addition, the VOCs exhibited nematicidal effect against Meloidogyne javanica. The results demonstrate that the VOCs produced by S. cerevisiae affect protein synthesis and the activity of enzymes associated to the vegetative growth in G. citricarpa. Thus, the fumigation using VOCs presents potential in the control of citrus black spot disease in post-harvest as well as of other organisms of agronomic importance. The present workalso contributed with new information regarding the role of the VOCs in the interactions among microorganisms in nature.