Hexadecane toxicity towards pure cultures of methanogens

Petroleum industry generates large volumes of hydrocarbon-containing wastewater, that may be treated and valorized by anaerobic conversion to methane. This process is performed by complex microbial communities and is only thermodynamically feasible at low hydrogen partial pressure, which is generally accomplished by the activity of hydrogenotrophic methanogens. However, alkanes, polyaromatic hydrocarbons and BTEX were shown to inhibit methanogenesis in mixed microbial cultures. This may be due to a direct inhibition of the methanogens, or may result from indirect inhibition, by disrupting the microbial relationships in the complex communities. To get more insights on this topic, the toxicity of aliphatic hydrocarbons towards pure cultures of hydrogenotrophic methanogens was assessed in this work. Aliphatic hydrocarbons represent the largest fraction of crude oil or petroleum-derived products, and hexadecane (HC) was chosen as model compound. Methane production from H2/CO2 (80:20%, 1.7x105 Pa) by Methanobacterium formicicum and Methanospirillum hungatei was measured in the presence of increasing HC concentrations (1, 5, 15 and 30 mM), and was compared with the controls without HC. For both methanogens, the methane production rate was significantly lower (p30 mM could be estimated for M. formicicum and M. hungatei, respectively. Therefore, M. hungatei is more tolerant to the presence of HC than M. formicicum, possibly due to the differences in cell wall structure and membrane lipid composition of the two species. Moreover, the relatively high IC50 values obtained are most likely related with the low HC solubility. Considering the typical range of hydrocarbon concentrations in wastewater from the petroleum industry, toxic effects from aliphatic hydrocarbons towards hydrogenotrophic methanogens will not be expected to occur during the anaerobic treatment of these type of wastewater.This study was supported by FCT under the scope of project MORE (PTDC/AAGTEC/3500/2014; POCI-01-0145-FEDER-016575), of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Patologias atuais: a compulsão e a sociedade dos excessos: Current pathologies: compulsion and the society of excesses

O artigo em tela tem por objetivo analisar os aspectos biopsicossociais da conduta compulsiva de consumo. Propõe-se a apresentar os elementos psicológicos contidos nesse comportamento, além de verificar quais são os resultados decorrentes dessa compulsão. O consumo compulsivo, também chamado de oniomania, é um transtorno causado pela ansiedade despertada pela necessidade de comprar e saciada, somente, quando é materializada a aquisição daquilo que se deseja comprar. O estudo em questão pode ser classificado como sendo de cunho bibliográfico, a partir da análise de documentos publicados em forma de artigos científicos e livros em formato digital

Estratégias para estimular a biorremediação de hidrocarbonetos

Programa doutoral em Gestão e Tratamento de ResíduosA contaminação ambiental por hidrocarbonetos constitui um grave problema, que requer o desenvolvimento de novas soluções para proteger e restaurar os ecossistemas. Técnicas de biorremediação têm sido descritas e incentivadas como abordagens eficientes e ecológicas. Neste trabalho, diferentes estratégias foram testadas para estimular a biorremediação de hidrocarbonetos, explorando vias aeróbias e anaeróbias de degradação. Corksorb, um biosorvente à base de cortiça utilizado em derrames de petróleo, promoveu o crescimento e a atividade de bactérias aeróbias hidrocarbonoclásticas. Na presença de corksorb, a degradação de alcanos por Rhodococcus opacus B4 foi mais elevada, i.e., 96±1 % relativamente a 88±3 % na ausência do biosorvente. Para Alcanivorax borkumensis SK2, o crescimento em alcanos foi 1,5 vezes maior nos ensaios com corksorb, e 72±2 % dos alcanos foram biodegradados, enquanto que na sua ausência a degradação foi de 47±2 %. Análise trascriptómica revelou um aumento da expressão genética para rRNA e tRNA, confirmando a maior atividade metabólica da A. borkumensis SK2 na presença de corksorb. Imagens de microscopia eletrónica de varrimento e menor expressão de genes que codificam para a formaçães de pili sugerem que a fixação das células ao corksorb foi determinante para o aumento da atividade. A existência de bactérias nativas degradadoras de alcanos no corksorb foi revelada. Assim, o uso de corksorb pode induzir um efeito combinado de sorção e estímulo da biodegradação, com elevado potencial na biorremediação in situ. A biodegradação anaeróbia de hidrocarbonetos é geralmente um processo lento. Nanomateriais condutores foram testados para acelerar a conversão de hidrocarbonetos a metano, nomeadamente nanotubos de carbono (CNT), CNT impregnados com 2 % de ferro (CNT@Fe) ou magnetite (MG). Quando se utilizou um sedimento ribeirinho recentemente contaminado com óleos como inóculo e fonte de carbono, o teor de hidrocarbonetos não se alterou significativamente ao longo do tempo, em todas as condições testadas, apontando para a ausência de atividade degradadora de hidrocarbonetos no sedimento. No entanto, a produção cumulativa de metano foi 10,2 e 4,5 vezes maior nos ensaios com CNT@Fe e CNT, respetivamente, quando comparada com os ensaios realizados sem nanomateriais, mostrando um efeito estimulador destes na degradação da matéria orgânica natural. Numa segunda experiência, 1-hexadeceno foi convertido a metano em quantidades quasi-estequiométricas, mas não houve estímulo pelos nanomateriais, possivelmente devido à incapacidade dos microrganismos para receberem/transferirem eletrões para os materiais. Globalmente, esta tese traz informação importante sobre o potencial de aplicação de um biosorvente (Corksorb) e de nanomateriais condutores na conversão aeróbia e anaeróbia de hidrocarbonetos, com vista à biorremediação in situ e ex situ de matrizes ambientais contaminadas ou resíduos oleosos. Estudos adicionais e investimento na investigação são necessários nesta área, para projetar e desenvolver novas estratégias de estímulo da biorremediação, uma vez que a recuperação de áreas poluídas por processos naturais é geralmente difícil, e o mundo tem urgência em encontrar soluções para a descontaminação de derrames de petróleo.Environmental contamination with hydrocarbons is a major problem that requires attention, in order to obtain novel solutions to protect and restore ecosystems. Bioremediation techniques have been described and empower as efficient and environmental friendly approaches in remediation processes. In this research, different strategies were tested for enhancing bioremediation of hydrocarbon-polluted environments, exploiting both aerobic and anaerobic degradation pathways. Corksorb, a cork-based biosorbent used in oil spills, was shown to promote the growth and activity of hydrocarbonoclastic bacteria. In the presence of corksorb, alkane degradation by Rhodococcus opacus B4 was enhanced, i.e. 96±1 % relatively to 88±3 % in the absence of the biosorbent. For Alcanivorax borkumensis SK2, growth in alkanes was 1,5 times higher in the presence of corksorb, and 71.6±1.9 % of the added alkanes were degraded, while in its absence only 47.3±1,5 % was converted. Transcriptomics analysis revealed an increased expression of rRNA and tRNA coding genes, which confirms the higher metabolic activity of A. borkumensis SK2 in the presence of corksorb. Scanning electron microscopy images and downregulation of pili formation coding genes, which are involved in cell mobility, suggest that cell attachment on corksorb is a determinant for the improved activity. The existence of native alkane-degrading bacteria in corksorb was revealed, which may assist in situ bioremediation. Hence, the use of corksorb in marine oil spills may induce a combined effect of sorption and stimulated biodegradation, with high potential for accelerating in situ bioremediation processes. In anoxic environments, anaerobic hydrocarbons biodegradation is generally a slow process. Conductive nanomaterials were tested to enhance hydrocarbons conversion to methane, namely carbon nanotubes (CNT), carbon nanotubes impregnated with 2 % iron (CNT@Fe) or magnetite (MG). When river sediments recently contaminated with oil were used as inoculum and also as carbon source, total petroleum hydrocarbons did not change significantly over time in all the conditions tested, thus pointing to the absence of hydrocarbon-degrading activity in the sediments. Nevertheless, cumulative methane production was 10,2 and 4,5 times higher in the assays with CNT@Fe and CNT, respectively, than in the assays without nanomaterials, showing a stimulatory effect in the degradation of the natural organic matter. In a second experiment, 1-hexadecene was converted to methane at close-to-stoichiometric amounts, but this process was not stimulated by the nanomaterials, possibly due to the inability of the microorganisms to receive/transfer electrons to the materials. Overall, this work gave important insights on the potential application of a biosorbent (Corksorb) and conductive nanomaterials on hydrocarbons conversion under aerobic or anaerobic conditions, for in situ and ex situ bioremediation of environmental contaminated matrixes, as well as petroleum-based oily wastes. More studies and research investments are required in these study fields to design and develop new strategies for enhanced hydrocarbons bioremediation, as the recovery of polluted areas by natural processes is generally difficult, and the world urges in finding solutions for oil spills decontamination

Water losses analysis of the captation, treatment and adduction systems of Andorinhas, Queimadela and Rabagão subsystems

Dissertação de mestrado integrado em Engenharia Biológica (área de especialização em Tecnologia do Ambiente)A crescente preocupação mundial com os gastos excessivos da utilização de água, bem como os custos associados à captação, tratamento e distribuição deste recurso às populações levam às entidades gestoras dos sistemas de tratamento e abastecimento de água implementar medidas de minimização de perdas de água, que ocorrem nos seus sistemas de tratamento. Na empresa Águas do Noroeste S.A. estão em curso medidas que pretendem a minimização das perdas de água nas estações de tratamento de água de Andorinhas, Queimadela e Rabagão. No subsistema de abastecimento das Andorinhas as perdas de água, no período em estudo, representam cerca de 90 000 m3. Os gastos energéticos associados a estas perdas de água representam 20 % da totalidade despendida. No subsistema de Queimadela, pelo período em estudo, foram verificadas perdas de água na ordem dos 88 000 m3. Da totalidade do valor gasto em energia, cerca de 6,7 % foram aplicados em perdas de água. No subsistema do Rabagão, pelo período em estudo, verificaram-se perdas superiores a 464 000 m3, estando este subsistema ainda em fase de arranque. Os gastos energéticos aplicados em perdas de água correspondem a 57 % do valor energético total. A aplicação de softwares informáticos como o EPANET 2.0 permite uma melhor gestão e perceção da ocorrência de perdas de água nas redes de distribuição, permitindo uma atuação mais rápida e eficaz na correção destas falhas.The increase of the international concern about water losses, as well as the higher costs associated with the collection, treatment and adduction of water to the population, has leaded the water treatment/distribution management entities into the implementation of measures for reduction of water losses that has been occurring in their own distribution systems. In Águas do Noroeste S.A. there are ongoing several actions in order to lower the water losses in water treatment stations of Andorinhas, Queimadela and Rabagão. In the subsystem of Andorinhas the water losses, in the study period, represent 90 000 m3. The energy costs spent in water losses were about 20 % of the main value spent in energy. In Queimadela subsystem the water losses were lost 88 000 m3 of water. From the main value of energy spending, there were 6,7 % who were applied in water losses. In the subsystem of Rabagão, in the research period, the water losses were 464 000 m3, approximately. Circa 57 % of the total amount spent on energy was applied in water losses. This subsystem is still in the beginning period. The application of software’s like EPANET 2.0 allows a better control and perception of the water losses occurrence in the distribution system, allowing faster and more efficient actions in the corrections of those fails

Microaeration in anaerobic digestion systems: effect of low oxygen concentrations on methanogenic communities

In anaerobic digestion (AD) systems, the coordinated activity of different microbial groups leads to the conversion of complex organic matter into methane. The presence of oxygen may cause negative effects on these processes, by inhibiting the growth and activity of obligate anaerobes, namely methanogens. Nevertheless, the exposure to small amounts of oxygen (microaeration) was shown to improve the AD processes, mainly by enhancing the activity of facultative bacteria. These bacteria promote the hydrolysis and fermentation of the organic macromolecules into various intermediates, using oxygen as final electron acceptor, thus increasing the availability of substrates for syntrophic bacteria and methanogens. The effect of low oxygen concentrations towards these two microbial groups has been seldom studied and was investigated in this work. For that, anaerobic sludge was incubated in batch bottles with acetate, H2/CO2 or ethanol until reaching the exponential growth phase. Then, second substrate addition was performed and oxygen was added at increasing concentrations (0, 0.5, 1.0, 2.5 and 5%). Compared with the controls (0% O2), O2 exposure significantly decreased the substrate consumption and initial methane production rate (MPR) from H2/CO2 or acetate, at all the concentrations tested. At 0.5% O2, MRP from these two substrates was inhibited by 31±5% and 39 ±10%, respectively. Nevertheless, the assays amended with acetate were incubated over 30 hours, and activity was recovered in the assays that received the lower % O2. In the assays with ethanol, significant effects on ethanol uptake, acetate production and MPR were only observed at 2.5% and 5% O2. At 2.5%, MRP inhibition was 36±7%. The lower impact of O2 in these assays may be related to stimulation of facultative bacteria by the presence of ethanol, that enhanced O2 removal from the media, allowing the methanogenic community to maintain its activity.This study was supported by FCT under the scope of project MORE (PTDC/AAGTEC/3500/2014; POCI-01-0145-FEDER-016575), of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte.info:eu-repo/semantics/publishedVersio

Enhanced oil spill bioremediation with Corksorb

Regranulated cork particles are by-products of cork stopper production, which present very high hydrophobicity and oil sorption capacity after thermal treatment [1]. These thermally treated granules have been used as absorbents in the remediation of oil spills under the commercial brand Corksorb (Corticeira Amorim, S.G.P.S.). Once saturated with oil, cork should be regenerated for cyclic reuse. For that, hydrocarbonoclastic bacteria can be applied to degrade the oil components. Here, we hypothesize that Corksorb granules can potentially stimulate the activity of these bacteria, due to their unique chemical composition, structure and properties [2], thus improving in situ bioremediation of oil spills. To test this hypothesis, bacterial growth and hydrocarbons biodegradation were assessed in pure cultures of Alcanivorax borkumensis SK2 or Rhodoccocus opacus B4 incubated with a mixture of alkanes, and compared with incubations in which the alkanes were sorbed in corksorb. Growth of Alcanivorax borkumensis SK2 in alkanes was 1.5 times higher in the assays with corksorb, relatively to the assays without corksorb. Moreover, 72% of the added alkanes were biodegraded in the presence of corksorb, while in its absence only 47% were removed. For Rhodococcus opacus B4, hydrocarbons consumption reached 96% and 88% in the presence and absence of corksorb, respectively, although no significant effect could be detected on growth. These results show that corksorb stimulates the activity of hydrocarbonoclastic bacteria, therefore presenting a high potential for improving in situ bioremediation of hydrocarbon-contaminated environments by combining absorption with stimulated biodegradation. The mechanisms underlying this stimulatory effect are currently under study.info:eu-repo/semantics/publishedVersio