Síntese de ésteres derivados do ácido oléico empregando lipases produzidas por Yarrowia lipolytica

Biodiesel é um biocombustível que consiste na mistura de ésteres monoalquílicos de ácidos graxos de cadeia longa. O processo usual de produção deste combustível é a transesterificação de óleos vegetais com álcoois de cadeia curta. Nesse processo, a matéria prima deve conter baixo conteúdo de ácido graxos livres ( ≤ 1%) e água (≤ 0,5%). Como alternativa ao processo de transesterificação, destaca-se o emprego de matérias-primas de baixo custo, com elevado teor de ácidos graxos livres, para a síntese de ésteres alquílicos através de reações de esterificação. As reações de produção do biodiesel podem ser catalisadas por via química (ácida e básica) ou enzimática. Na catálise enzimática, os biocatalisadores empregados são as lipases, que catalisam a hidrólise e síntese de ésteres e podem ser obtidas a partir de microrganismos, plantas ou tecido animal, sendo as de origem microbiana as mais utilizadas. O objetivo principal deste trabalho foi avaliar o potencial da lipase de Yarrowia lipolytica, uma levedura não convencional, na síntese de ésteres do ácido oleico visando à obtenção de ésteres alquílicos (biodiesel). Foram estudados os efeitos da temperatura (25, 30, 35, 40, 50 e 60oC), do teor enzimático (5, 10, 20, 30 e 40% v/v) e do tipo de álcool (metanol, etanol, n-propanol e n-butanol ) nas reações de esterificação do ácido oleico empregando o extrato enzimático líquido produzido por Yarrowia lipolytica. Os resultados obtidos mostraram que as reações conduzidas a 30oC e com 10% v/v do extrato enzimático apresentaram maior taxa inicial de reação. Também foi avaliada a utilização do extrato enzimático liofilizado (5% m/v) e do PES (produto enzimático sólido) (5% m/v) de Yarrowia lipolytica na reação de esterificação do ácido oleico com n-butanol a 30oC. O maior consumo de ácido oleico ocorreu na reação conduzida com o PES. O efeito da temperatura (25, 30, 35, 40 e 50oC) na síntese de oleato de butila foi, então, investigado nas reações empregando PES como biocatalisador e a maior conversão de ácido oleico foi verificada na temperatura de 40oC

Uso da calibração multivariada para a predição de propriedades físico-químicas de misturas de óleo de soja e biodiesel

O objetivo deste trabalho foi estabelecer um modelo empregando-se ferramentas de regressão multivariada para a previsão do teor em ésteres metílicos e, simultaneamente, de propriedades físico-químicas de misturas de óleo de soja e biodiesel de soja. O modelo foi proposto a partir da correlação das propriedades de interesse com os espectros de reflectância total atenuada no infravermelho médio das misturas. Para a determinação dos teores de ésteres metílicos foi utilizada a cromatografia líquida de alta eficiência (HPLC), podendo esta ser uma técnica alternativa aos método de referência que utilizam a cromatografia em fase gasosa (EN 14103 e EN 14105). As propriedades físico-químicas selecionadas foram índice de refração, massa específica e viscosidade. Para o estudo, foram preparadas 11 misturas com diferentes proporções de biodiesel de soja e de óleo de soja (0-100 % em massa de biodiesel de soja), em quintuplicata, totalizando 55 amostras. A região do infravermelho estudada foi a faixa de 3801 a 650 cm-1. Os espectros foram submetidos aos pré-tratamentos de correção de sinal multiplicativo (MSC) e, em seguida, à centralização na média (MC). As propriedades de interesse foram submetidas ao autoescalamento. Em seguida foi aplicada análise de componentes principais (PCA) com a finalidade de reduzir a dimensionalidade dos dados e detectar a presença de valores anômalos. Quando estes foram detectados, a amostra era descartada. Os dados originais foram submetidos ao algoritmo de Kennard-Stone dividindo-os em um conjunto de calibração, para a construção do modelo, e um conjunto de validação, para verificar a sua confiabilidade. Os resultados mostraram que o modelo proposto por PLS2 (Mínimos Quadrados Parciais) foi capaz de se ajustar bem os dados de índice de refração e de massa específica, podendo ser observado um comportamento aleatório dos erros, indicando a presença de homocedasticidade nos valores residuais, em outras palavras, o modelo construído apresentou uma capacidade de previsão para as propriedades de massa específica e índice de refração com 95% de confiança. A exatidão do modelo foi também avaliada através da estimativa dos parâmetros de regressão que são a inclinação e o intercepto pela Região Conjunta da Elipse de Confiança (EJCR). Os resultados confirmaram que o modelo MIR-PLS desenvolvido foi capaz de prever, simultaneamente, as propriedades índice de refração e massa específica. Para os teores de éteres metílicos determinados por HPLC, foi também desenvolvido um modelo MIR-PLS para correlacionar estes valores com os espectros de MIR, porém a qualidade do ajuste não foi tão boa. Apesar disso, foi possível mostrar que os dados podem ser modelados e correlacionados com os espectros de infravermelho utilizando calibração multivariada

Estudo da reação entre o metanol e o acetato de etila em catalisadores Mg/La por espectroscopia no infravermelho acoplada a espectrometria de massas

A transesterificação metílica em meio homogêneo é catalisada por bases, tais como hidróxidos e alcóxidos de sódio ou potássio e se processa em baixa temperatura de reação, mesmo em escala industrial. A utilização de catalisadores formados por sólidos básicos aparece como uma alternativa promissora aos processos homogêneos convencionais, tendo em vista as inúmeras vantagens como a redução da ocorrência das reações indesejáveis de saponificação e redução de custos dos processos pela diminuição do número de operações associadas. Em estudos anteriores realizados pelo grupo, catalisadores a base de Mg/La com diferentes composições químicas (9:1, 1:1 e 1:9) mostraram-se promissores para a obtenção de ésteres metílicos via reação de transesterificação, porém não foi possível fazer uma correlação entre atividade catalítica e as propriedades físico-químicas quando toda a série foi considerada. Assim, a realização de um estudo de caráter fundamental, baseado em reações modelo e uso de moléculas sonda, permite avançar no entendimento das propriedades de superfície destes catalisadores. Portanto, o presente trabalho estuda a reação entre metanol e acetato de etila em catalisadores a base de Mg/La utilizando espectroscopia de reflectância difusa no infravermelho com transformada de Fourier (DRIFTS) acoplada a espectrometria de massas (MS) identificando os intermediários e produtos formados para determinar a rota reacional. As análises de difração de raios X mostram que os precursores são predominantemente compostos por carbonatos hidratados de magnésio (Mg/La 1:1 e 9:1) e de lantânio (Mg/La 1:9). Os perfis de decomposição térmica e difratogramas de raios X obtidos a partir de tratamento térmico in situ indicaram que estes carbonatos se decompõem apenas a partir de 750 C. As análises de Dessorção a Temperatura Programada realizadas com moléculas sonda, metanol e acetato de etila, mostraram a adsorção em maior quantidade do metanol independente da composição química do sólido. A partir dos resultados obtidos por DRIFTS-MS foi proposta uma rota reacional para a reação de transesterificação do acetato de etila e metanol, que ocorre via adsorção do metanol e do acetato de etila na superfície do catalisador, seguida da formação de um intermediário tetraédrico formado pelas moléculas adsorvidas, que sofre um rearranjo formando etanol, acetato de metila, acetona e metano. Simultaneamente, parte do metanol adsorvido como metoxi monodentado é desidrogenado formando formiatos que são dessorvidos na forma de formaldeído e decompostos formando CO2 e H2

Carboxilesterase na adaptação do metabolismo de lipídios do pacu à hipoxia

Os peixes são vertebrados que vivem em vários habitats. Adaptações de sua fisiologia e de sua bioquímica são estudadas para entender como conseguem sobreviver aos desafios presentes em cada ambiente. A diminuição da concentração de oxigênio dissolvido na água é um fenômeno natural cíclico em águas do Pantanal e da Amazônia. A crescente poluição antrópica dos rios da Amazônia e do Pantanal pode, somada à hipoxia, oferecer ameaça à permanência de muitas espécies de peixes. Ao estudarmos a carboxilesterase (CarbE), enzima importante para a biotransformação de xenobióticos, observamos que sua atividade diminuía em plasma de pacu, um peixe típico do Pantanal, mantido em hipoxia durante 42 horas. As carboxilesterases participam de inúmeras reações químicas no organismo, incluindo uma transesterificação capaz de produzir ésteres etílicos tóxicos de ácido graxo (FAEE, fatty acid ethyl esters) a partir de etanol e ésteres de ácidos graxos. Já que a diminuição da atividade de CarbE poderia ser uma vantagem, pois que o etanol (um produto da glicólise em peixes sob hipoxia) seria menos esterificado, resolvemos saber mais sobre a bioquímica da CarbE do plasma e do fígado de pacus. Os pacus foram submetidos à hipoxia por diminuição da concentração até 0,5 mg O2/L por meio de borbulhamento de nitrogênio na água. Os animais ficaram nessas condições por 42 horas, quando então coletamos sangue e retiramos seus fígados. A atividade de CarbE ensaiada foi 50% menor no soro e 25% menor nos microssomos de fígado se comparada com a de peixes sob 6 mg O2/L. A CarbE isolada do soro dos pacus em normoxia possui massa molecular relativa de 56.000. A eletroforese em gel desnaturante com a fração purificada rendeu três bandas, mas o gel nativo apresentou só duas bandas com atividades sobre α-naftil acetato. Inferimos que mais do que uma isoforma da enzima está no plasma dos pacus. A CarbE isolada do soro não possui atividade de lipase sobre o Tween 20, mas os microssomos dos fígados dos animais em normoxia e hipoxia possuem. No entanto, a CarbE possui atividade sobre acil-CoA assim como o microssomo de fígado. A enzima pura apresenta Vmáx três vezes maior e uma KM quatro vezes maior do que a atividade presente nos microssomos. Além disso, os microssomos do fígado dos pacus em normoxia podem hidrolisar acil-CoA com o dobro da velocidade daqueles em hipoxia. A atividade clássica de CarbE do soro foi inibida por 4-HNE a 4 mM. A atividade de acil-CoA dos microssomos de fígado também foi sensível a 4-HNE a 4 mM, enquanto 2 mM de 4-HNE inibiu metade desta atividade do soro.

Studies on fish lipids. Pt. 2. Fatty acid composition of lipids of oil sardine (Sardinella longiceps)

Gas-liquid chromatography has been employed for the qualitative and quantitative analysis of the component fatty acids in lipids of oil sardine (Sardinella longiceps). Phospholipids and triglycerides of the lipids were previously separated by column chromatography before they were converted into the methyl esters of the fatty acids. The predominant acids present in the depot fat of the fish have been found to be C14:0=8.13%, C16:0=27.9%, C18:0=3.8%, C18:1=15.4%., C20:5=10.6% and C22:6=8.8%. Apart from the above acids the distribution of minor acids belonging to Cl8, C20 and C22 groups have also been worked out. The separated phospholipid fraction contained more than 70% polyunsaturated acids of which the important constituents were docosahexaenoic (C22:6=28%) and eicosapentaenoic (C20:5=10.6%). A marked reduction was found in the amounts of polyunsaturated acids in triglycerides, their total amount registering about 20%. This fraction recorded about 48% of C16 acids of which palmitic and palmitoleic acids amounted to 25.8% and 19.1% respectively. Occurrence of odd numbered fatty acids C15 and C17 has also been noted in the phospholipid and composite samples of the fish.

New (1R,4R)-2-arylidene-p-menthan-3-ones with a bridging ester group in the arylidene fragment. Synthesis and behavior in liquid-crystalline systems

(1R,4R)-2-(4-Hydroxybenzylidene)- and (1R,4R)-2-(4′-hydroxybiphenyl- 4-yl)methylene-p-menthan-3-ones were synthesized by condensation of (-)-menthone with O-tetrahydropyran-2-yl derivatives of 4-hydroxybenzaldehyde and 4′-hydroxy-4-formylbiphenyl, respectively, in a DMSO - base medium followed by the removal of the protective group. The reactions of these hydroxy derivatives with 4-alkylbenzoic, 4-alkyloxybenzoic, trans-4-alkylcyclohexane-4- carboxylic, and 4′-alkylbiphenyl-4-carboxylic acids afforded three series of new chiral esters. Compounds containing the arylidene moiety with three benzene rings were found to exhibit liquid-crystalline properties. The characteristic features of these compounds are discussed based on the results of studies by polarizing microscopy, differential scanning calorimetry, and small-angle X-ray scattering. It was found that the mesomorphic compounds under study can form a smectic A mesophase, twist grain boundary mesophases (TGBA), and blue phases in a wide temperature range. Upon dissolution of certain of chiral compounds in 4′-cyano-4-pentylbiphenyl, a rather high twisting power and the thermal stabilizing effect on mesophases were observed.

Evaluation of biochemical characteristics of a traditional salt fermented fish product of northeast India with special reference to its flavour components

'Lona ilish', is a traditional salt fermented fish product, widely consumed and very popular in north-east part of India and Bangladesh. It is prepared exclusively from a high fat fish, Hilsa (Tenualosa) ilisha. 'Lona ilish' was prepared in the laboratory following traditional process. After 150 days of fermentation, a better quality 'lona ilish' was obtained. Biochemical characteristics of market sample was estimated and compared with the laboratory prepared one. A variation in biochemical composition was observed. Sensory quality of the final product of laboratory prepared 'lona ilish' was compared with the market sample and found that the laboratory prepared product scored better than the market sample. The moisture (49.89%) and salt (15.48%) of the final product was found to be satisfactory for stability of the 'lona ilish' at ambient temperature. Analysis of volatile compounds of 'lona ilish' was done using GC-MS. It was concluded that, aldehydes, ketones and esters may possibly contribute characteristic aromas to the overall flavour of the salt fermented hilsa.

The effect of artisanal preservation methods on nutritional security of “Mukene” Rastrineobola argentea caught from Lakes Victoria and Kyoga in Uganda

The artisanal fish preservation methods in Uganda are characterized by extreme operating conditions. Consequently, vital nutritional components diminish in value and quantity which renders fish consumer nutritionally insecure. To establish the magnitude of nutritional loss, duplicate samples of Mukene Rastrineobola argentea were collected from Kiyindi landing site on L. Victoria and Moone landing site on L. Kyoga. Each set of duplicate samples was divided into five portions and kept on ice. For each preservation method a portion was processed into respective products at Food Bioscience and Agri-Business Laboratories aside from the control (fresh) sample. Both preserved and control samples were analysed for nutrient loss at Department of Chemistry, Makerere University using AOAC methods. The composition of fatty acids was determined by methanolysis gas chromatography and Mass spectrophotometry of the resultant methyl esters. The results indicate that nutrients of all preserved samples did not vary significantly from the control except for some fatty acids. The Eicosapentaenoic acid (EPA) in fresh samples declined from 6.72% to 1.08% in deep-fried samples constituting 83.93% nutrient loss. The sum ratio w3:w6 as well as EPA: DHA (Docosahexaenoic) ratio in fried samples also varied significantly (p<0.5) lower than 0.668 and 0.20 for the average of either preservation methods and experts recommended ratio respectively. Further research has been recommended to ascertain the causative factor, since Mukene frying is being promoted in the Great lakes region as alternative method to sun-drying. In conclusion, regular consumers of fried Mukene do not benefit much from the nutritional and health attributes of Omega 3 and 6.

Spray combustion characteristics of palm biodiesel

The potential of palm methyl esters (PME) as an alternative fuel for gas turbines is investigated using a swirl burner. The main air flow is preheated to 623 K, and a swirling spray flame is established at atmospheric pressure. The spray combustion characteristics of PME are compared to diesel and Jet-A1 fuel under the same burner power output of 6 kW. Investigation of the fuel atomizing characteristics using phase Doppler anemometry (PDA) shows that most droplets are distributed within the flame reaction zone region. PME droplets exhibit higher Sautermean diameter (SMD) values than baseline fuels, and thus higher droplet penetration length and longer evaporation timescales. The PME swirl flame presents a different visible flame reaction zone while combusting with low luminosity and produces no soot. NO x emissions per unit mass of fuel and per unit energy are reduced by using PME relative to those of conventional fuels. © 2012 Copyright Taylor and Francis Group, LLC.

Effects of the biodiesel fuel physical properties on the swirl stabilised spray combustion characteristics

An increasin g interest in biofuel applications in modern engines requires a better understanding of biodiesel combustion behaviour. Many numerical studies have been carried out on unsteady combustion of biodiesel in situations similar to diesel engines, but very few studies have been done on the steady combustion of biodiesel in situations similar to a gas turbine combustor environment. The study of biodiesel spray combustion in gas turbine applications is of special interest due to the possible use of biodiesel in the power generation and aviation industries. In modelling spray combustion, an accurate representation of the physical properties of the fuel is a first important step, since spray formation is largely influenced by fuel properties such as viscosity, density, surface tension and vapour pressure. In the present work, a calculated biodiesel properties database based on the measured composition of Fatty Acid Methyl Esters (FAME) has been implemented in a multi-dimensional Computational Fluid Dynamics (CFD) spray simulation code. Simulations of non-reacting and reacting atmospheric-pressure sprays of both diesel and biodiesel have been carried out using a spray burner configuration for which experimental data is available. A pre-defined droplet size probability density function (pdf) has been implemented together with droplet dynamics based on phase Doppler anemometry (PDA) measurements in the near-nozzle region. The gas phase boundary condition for the reacting spray cases is similar to that of the experiment which employs a plain air-blast atomiser and a straight-vane axial swirler for flame stabilisation. A reaction mechanism for heptane has been used to represent the chemistry for both diesel and biodiesel. Simulated flame heights, spray characteristics and gas phase velocities have been found to compare well with the experimental results. In the reacting spray cases, biodiesel shows a smaller mean droplet size compared to that of diesel at a constant fuel mass flow rate. A lack of sensitivity towards different fuel properties has been observed based on the non-reacting spray simulations, which indicates a need for improved models of secondary breakup. By comparing the results of the non-reacting and reacting spray simulations, an improvement in the complexity of the physical modelling is achieved which is necessary in the understanding of the complex physical processes involved in spray combustion simulation. Copyright © 2012 SAE International.

Spray flame structure of rapeseed biodiesel and Jet-A1 fuel

The spray combustion characteristics of rapeseed methyl esters (RME) were compared to Jet-A1 fuel using a gas turbine type combustor. The swirling spray flames for both fuels were established at a constant power output of 6 kW. The main swirling air flow was preheated to 350 C prior to coaxially enveloping the airblast-atomized liquid fuel spray at atmospheric pressure. Investigation of the fundamental spray combustion was performed via measurements of the fuel droplet sizes and velocities, gas phase flow fields and flame reaction zones. The spray flame droplets and flow fields in the combustors were characterised using phase Doppler anemometry (PDA) and particle imaging velocimetry (PIV) respectively. Flame chemiluminescence imaging was employed to identify the flame reaction zones. The highest droplet concentration zone extends along a 30 angle from the symmetry axis, inside the flame zone. Only small droplets(<17 μ) (<17 μm)are found around the centreline region, while larger droplets are found at the edge of the spray outside the flame reaction zone. RME exhibits spray characteristics similar to Jet-A1 but with droplet concentration and volume fluxes four times higher, consistent with the expected longer droplet evaporation timescale. The flow field characteristics for both RME and Jet-A1 spray flames are very similar despite the significantly different visible characteristics of the flame reaction zones. © 2013 Elsevier Ltd. All rights reserved.

ANTHROPOGENIC ORGANIC CONTAMINANTS IN WATER AND SURFACE SEDIMENTS OF LARGE SHALLOW EUTROPHIC CHAOHU LAKE, CHINA

To characterize the contamination of anthropogenic organic contaminants in the aquatic environment of Chaohu Lake, China, 7 samples for both water and surface sediment were collected in the lake. Organic contaminants were extracted by solid phase extraction (SPE) and Soxhlet extraction from the water and surface sediment samples, respectively, and then analyzed by GC-MS. One hundred and twenty kinds of organic chemicals were detected in these samples including phenol, benzene series, benzaldehydes, ethanol, polycyclic aromatic hydrocarbons (PAHs), sulfur compounds, alcoholic halides, amines, ketones, esters, alkenes and alkanes. Among them, 13 kinds of chemicals were identified as priority pollutants listed by the U.S. Environmental Protection Agency (EPA), such as phthalate esters (PAEs) and PAHs. Besides, the concentrations of 19 of PAEs and PAHs including, priority pollutants identified were also determined. Bis(2-ethylhexyl)phthalate, the predominant component of the analyzed pollutants, was in the range from 72.34 ng g(-1) DW to 613.71 ng g(-1) DW, 14.80 ng L-1 to 47.05 ng L-1 in sediment and water, respectively. The results indicated that the northwest part of the lake was heavily polluted by domestic and industrial wastewater.

Effects of constructed wetland system on the removal of dibutyl phthalate (DBP)

Phthalic acid esters (PAEs) have become widely diffused in the environment via the manufacturing process. Numerous experiments have shown that the bioaccumulation of PAEs occurred in the aquatic and terrestrial food chain; meanwhile, it was found that some of PAEs were considered as potential carcinogens, teratogens and mutagens. In this research, two vertical/reverse-vertical flow constructed wetland systems were set up to study its removal efficiency of dibutyl, phthalate (DBP) pollution. The results showed that the constructed wetland system could remove DBP effectively, and the removal rates reached nearly 100%. Substrate microorganism and enzymatic activities probably played key roles during DBP removal, and the removal of DBP probably mainly took place in the upper layer of chamber A in the constructed wetland systems. (C) 2007 Elsevier GmbH. All rights reserved.

Discrete multicomponent model for biodiesel spray combustion simulation

An important first step in spray combustion simulation is an accurate determination of the fuel properties which affects the modelling of spray formation and reaction. In a practical combustion simulation, the implementation of a multicomponent model is important in capturing the relative volatility of different fuel components. A Discrete Multicomponent (DM) model is deemed to be an appropriate candidate to model a composite fuel like biodiesel which consists of four components of fatty acid methyl esters (FAME). In this paper, the DM model is compared with the traditional Continuous Thermodynamics (CTM) model for both diesel and biodiesel. The CTM model is formulated based on mixing rules that incorporate the physical and thermophysical properties of pure components into a single continuous surrogate for the composite fuel. The models are implemented within the open-source CFD code OpenFOAM, and a semi-quantitative comparison is made between the predicted spray-combustion characteristics and optical measurements of a swirl-stabilised flame of diesel and biodiesel. The DM model performs better than the CTM model in predicting a higher magnitude of heat release rate in the top flame brush region of the biodiesel flame compared to that of the diesel flame. Using both the DM and CTM models, the simulation successfully reproduces the droplet size, volume flux, and droplet density profiles of diesel and biodiesel. The DM model predicts a longer spray penetration length for biodiesel compared to that of diesel, as seen in the experimental data. Also, the DM model reproduces a segregated biodiesel fuel vapour field and spray in which the most abundant FAME component has the longest vapour penetration. In the biodiesel flame, the relative abundance of each fuel component is found to dominate over the relative volatility in terms of the vapour species distribution and vice versa in the liquid species distribution. © 2014 Elsevier Ltd. All rights reserved.

Enzymatic activities in constructed wetlands and di-n-butyl phthalate (DBP) biodegradation

The bioaccumulation of phthalate acid esters (PAEs) from industrial products and their mutagenic action has been suggested to be a potential threat to human health. The effects of the most frequently identified PAE, Di-n-butyl phthalate (DBP), and its biodegradation, were examined by comparison of two small scale plots (SSP) of integrated vertical-flow constructed wetlands. The influent DBP concentration was 9.84 mg l(-1) in the treatment plot and the control plot received no DBP. Soil enzymatic activities of dehydrogenase, catalase, protease, phosphatase, urease, cellulase, beta-glucosidase, were measured in the two SSP after DBP application for 1 month and 2 months, and 1 month after the final application. Both treatment and control had significantly higher enzyme activity in the surface soil than in the subsurface soil (P < 0.001) and greater enzyme activity in the down-flow chamber than in the up-flow chamber (P < 0.05). In the constructed wetlands, DBP enhanced the activities of dehydrogenase, catalase, protease, phosphatase and inhibited the activities of urease, cellulase and beta-glucosidase. However, urease, cellulase, beta-glucosidase activities were restored 1 month following the final DBP addition. Degradation of DBP was greater in the surface soil and was reduced in sterile soil, indicating that this process may be mediated by aerobic microorgansims. DBP degradation fitted a first-order model, and the kinetic equation showed that the rate constant was 0.50 and 0.17 d(-1), the half-life was 1.39 and 4.02 d, and the r(2) was 0.99 and 0.98, in surface and subsurface soil, respectively. These results indicate that constructed wetlands are able to biodegrade organic PA-Es such as DBP. (c) 2005 Elsevier Ltd. All rights reserved.