High Ester Content Research Articles

Investigation of biodiesel production by HUSY and Ce/HUSY zeolites: Influence of structural and acidity parameters

In this work, activities of HUSY and Ce/HUSY zeolites were studied in transesterification cycles of soybean oil and ethanol to produce biodiesel. The characterization of the materials was performed by FT-IR, XRD, BET method and pyridine adsorption followed by thermal analyses. TG/DTG results indicated a decrease of acid sites for both samples after each reaction cycle. However, Ce/HUSY zeolite showed a superior stabilization of acidic sites after three catalytic cycles and intermediary activation procedures. Biodiesel production exhibited high conversion levels (>96%) for both zeolites in all transesterification cycles. Surface area and pore volume measurements evidenced that cerium incorporation reduced the number of acid sites by interacting with OH groups in the micropore and external area of the zeolitic surface. This interaction resulted in an acid and structural stability, which provided a better activity (99%) than HUSY (96%). The higher conversion values obtained by zeolites showed a final product with a different distribution when compared with the traditional transesterification process. The identification of free fatty acids, diethyl and glycerol ethers in the final products and the reduction of unsaturated compounds indicated that parallel reactions also occurred in the studied systems. Nonetheless, the biofuel produced showed high ester content and did not present changes in its calorific power.

Thermogravimetry and Viscometry for Assessing the Ester Content (FAME and FAEE)

Biodiesel is a biofuel that is of great importance; its good performance is associated with its purity mainly related to a high content of fatty acid alkyl esters, quantified by gas chromatography (GC), liquid chromatography (LC), hydrogen nuclear magnetic resonance (1H-NMR) and infrared (FTIR) spectroscopy. However, these methodologies take long a time and are relatively expensive. Herein, thermogravimetric analysis (TGA) and viscometry (VA) are studied as alternative methods for the quantification of alkyl esters (FAME and FAEE). Analytical curves from the viscosity and mass loss percentage (TGA) as a function of methyl and ethyl ester levels on binary mixtures (soybean biodiesel/soybean oil) were constructed. The correlations experimentally obtained were presented and used to quantify biodiesel content in the products of ethanolysis and methanolysis and in biodiesel/vegetable oil mixtures of different feedstocks. This comparative study confirmed that both alternative methods are adequate to be used. A single viscometry analytical curve could be used to analyze products, obtained by different oleaginous plants, if their oils exhibit similar viscosities. Viscometry can be the most suitable alternative technique because it is portable, fast, less sensitive to the presence of intermediates than thermogravimetric analysis, easy to work with and very inexpensive.

Characterization of aromatic volatile constituents in 11 Asian pear cultivars belonging to different species

Aroma is an important fruit sensory attributes that is influenced by the volatile compounds present in the fruit, and it determines whether a fruit is acceptable to consumers. The volatile compounds in 11 pear cultivars from different species were investigated by headspace solid phase microextraction and gas chromatography-mass spectrometry. In total, 70 volatile compounds, including three alcohols, six aldehydes, fifty-two esters, three acids, three terpenes and three ketones were identified and quantified. Ester was the dominant chemical class of which a total of 52 compounds were detected. Hexanal, hexyl acetate, ethyl hexanoate, ethyl 2-methylbutanoate and ethyl butanoate were the major volatile compounds. Pyrus ussuriensis Maxim showed a higher concentration of volatiles and higher ester content than in the other Asian pear species studied. Cultivars were clearly grouped into four clusters based on the concentration and number of different volatile compounds present in each cultivar. The clusters of different cultivars could be discriminated from each others using the first two principal components. The volatile profiles of the pears were qualitatively and quantitatively influenced by the cultivar. Key words: Pyrus, Asian pear, volatile compound, gas chromatography mass spectrometry (GC-MS), solid phase microextraction (SPME), multivariate analysis.

Free and bound aroma compounds characterization by GC‐MS of Negroamaro wine as affected by soil management

Negroamaro is an autochthonous wine grape variety of Southern Italy, which is becoming very important for the Italian wine market. The wine aroma is primary affected by the chemical composition of grapes, which can be influenced also by agronomic practices such as soil management. In this study, the free and bound aroma characterization was performed by gas chromatography-mass spectrometry analyses, and the influence of two soil managements (cover cropping and soil tillage) was evaluated. A total of 40 volatile compounds were observed in the wine samples. Alcohols (55.7 mg/L), fatty acids (7.0 mg/L) and esters (6.6 mg/L) were found as the main classes in Negroamaro wine. The results showed that the aroma composition of Negroamaro wine was positively affected by soil tillage probably because of the higher water stress (ψ(s)) recorded in the vines from this treatment. Indeed, among the free volatile compounds, higher contents of esters, carboxylic acids, alcohols, phenolics and acetamides together with lower contents of sulfurs compounds were found in soil tillage wine. Conversely, no difference was observed in glycoside volatile compounds.

Production of phenols and biofuels by catalytic microwave pyrolysis of lignocellulosic biomass

Catalytic microwave pyrolysis of biomass using activated carbon (AC) was investigated to determine the effects of pyrolytic conditions on the yields of phenol and phenolics. Bio-oils with high concentrations of phenol (38.9%) and phenolics (66.9%) were obtained. These levels were higher than those obtained by pyrolysis without AC addition and were closely related to the decomposition of lignin. A high concentration of esters (42.2% in the upgraded bio-oil) was obtained in the presence of Zn powder as catalyst and formic acid/ethanol as reaction medium. Most of the esters identified by GC–MS were long chain fatty acid esters. The high content of phenols and esters obtained in this study can be used as partial replacement of petroleum fuels after separation of oxygenates or as feedstock for organic syntheses in the chemical industry after purification.

Optimization of Sunflower Oil Transesterification Process Using Sodium Methoxide

In this study, the methanolysis process of sunflower oil was investigated to get high methyl esters (biodiesel) content using sodium methoxide. To reach to the best process conditions, central composite design (CCD) through response surface methodology (RSM) was employed. The optimal conditions predicted were the reaction time of 60 min, an excess stoichiometric amount of alcohol to oil ratio of 25%w/w and the catalyst content of 0.5%w/w, which lead to the highest methyl ester content (100%w/w). The methyl ester content of the mixture from gas chromatography analysis (GC) was compared to that of optimum point. Results, confirmed that there was no significant difference between the fatty acid methyl ester content of sunflower oil produced under the optimized condition and the experimental value (P ≥ 0.05). Furthermore, some fuel specifications of the resultant biodiesel were tested according to American standards for testing of materials (ASTM) methods. The outcome showed that the methyl ester mixture produced from the optimized condition met nearly most of the important biodiesel specifications recommended in ASTM D 6751 requirements. Thus, the sunflower oil methyl esters resulted from this study could be a suitable alternative for petrol diesels.

Solubility of nitrogen in marine mammal blubber depends on its lipid composition

Understanding the solubility of nitrogen gas in tissues is a crucial aspect of diving physiology, especially for air-breathing tetrapods. Adipose tissue is of particular interest because of the high solubility of nitrogen in lipids. Surprisingly, nothing is known about nitrogen solubility in the blubber of any marine mammal. We tested the hypothesis that N(2) solubility is dependent on the lipid composition of blubber; most blubber is composed of triacylglycerols, but some toothed whales deposit large amounts of waxes in blubber instead. The solubility of N(2) in the blubber of 13 toothed whale species ranged from 0.062 to 0.107 ml N(2) ml(-1) oil. Blubber with high wax ester content had higher N(2) solubility, observed in the beaked (Ziphiidae) and small sperm (Kogiidae) whales, animals that routinely make long, deep dives. We also measured nitrogen solubility in the specialized cranial acoustic fat bodies associated with echolocation in a Risso's dolphin; values (0.087 ml N(2) ml(-1) oil) were 16% higher here than in its blubber (0.074 ml N(2) ml(-1) oil). As the acoustic fats of all Odontocetes contain waxes, even if the blubber does not, these tissues may experience greater interaction with N(2). These data have implications for our understanding and future modeling of diving physiology in Odontocetes, as our empirically derived values for nitrogen solubility in toothed whale adipose were up to 40% higher than the numbers traditionally assumed in marine mammal diving models.

A lipoprotein source of cholesteryl esters is essential for proliferation of CEM-CCRF lymphoblastic cell line

Tumour are characterised by a high content of cholesteryl esters (CEs) stored in lipid droplets purported to be due to a high rate of intracellular esterification of cholesterol. To verify whether and which pathways involved in CE accumulation are essential in tumour proliferation, the effect of CE deprivation, from both exogenous and endogenous sources, on CEM-CCRF cells was investigated. Cholesterol synthesis, esterification and content, low-density lipoprotein (LDL) binding and high-density lipoprotein (HDL)-CE uptake were evaluated in cultured in both conventional and delipidated bovine serum with or without oleic or linoleic acids, cholesteryl oleate, LDL and HDL. High content of CEs in lipid droplets in this cell line was due to esterification of both newly synthesised cholesterol and that obtained from hydrolysis of LDL; moreover, a significant amount of CE was derived from HDL-CE uptake. Cell proliferation was slightly affected by either acute or chronic treatment up to 400 μM with Sz-58035, an acyl-cholesteryl cholesterol esterification inhibitor (ACAT); although when the enzyme activity was continuously inhibited, CE content in lipid droplets was significantly higher than those in control cells. In these cells, analysis of intracellular and medium CEs revealed a profile reflecting the characteristics of bovine serum, suggesting a plasma origin of CE molecules. Cell proliferation arrest in delipidated medium was almost completely prevented in the first 72 h by LDL or HDL, although in subsequent cultures with LDL, it manifested an increasing mortality rate. This study suggests that high content of CEs in CEM-CCRF is mainly derived from plasma lipoproteins and that part of CEs stored in lipid droplets are obtained after being taken up from HDL. This route appears to be up-regulated according to cell requirements and involved in low levels of c-HDL during cancer. Moreover, the dependence of tumour cells on a source of lipoprotein provides a novel impetus in developing therapeutic strategies for use in the treatment of some tumours.

Process engineering and optimization of glycerol separation in a packed-bed reactor for enzymatic biodiesel production

A process model for efficient glycerol separation during methanolysis in an enzymatic packed-bed reactor (PBR) was developed. A theoretical glycerol removal efficiency from the reaction mixture containing over 30% methyl esters was achieved at a high flow rate of 540ml/h. To facilitate a stable operation of the PBR system, a batch reaction prior to continuous methanolysis was conducted using oils with different acid values and immobilized lipases pretreated with methyl esters. The reaction system successfully attained the methyl ester content of over 30% along with reduced viscosity and water content. Furthermore, to obtain a high methyl ester content above 96% continuously, long-term lipase stability was confirmed by operating a bench-scale PBR system for 550h, in which the intermediates containing methyl esters and residual glycerides were fed into the enzyme-packed columns connected in series. Therefore, the developed process model is considered useful for industrial biodiesel production.

Preparation of fatty acid methyl esters from hazelnut, high-oleic peanut and walnut oils and evaluation as biodiesel

Refined hazelnut, walnut and high-oleic peanut oils were converted into fatty acid methyl esters using catalytic sodium methoxide and evaluated as potential biodiesel fuels. These feedstocks were of interest due to their lipid production potentials (780–1780Lha−1yr−1) and suitability for marginal lands. Methyl oleate was the principal constituent identified in hazelnut (HME; 76.9%) and peanut (PME; 78.2%) oil methyl esters. Walnut oil methyl esters (WME) were comprised primarily of methyl esters of linoleic (60.7%), oleic (15.1%) and linolenic (12.8%) acids. PME exhibited excellent oxidative stability (IP 21.1h; EN 14112) but poor cold flow properties (CP 17.8°C) due to its comparatively high content of very-long chain fatty esters. WME provided low derived cetane number and oxidative stability (IP 2.9h) data as a result of its high percentage of polyunsaturated fatty esters. HME yielded a satisfactory balance between all fuel properties when compared to the biodiesel standards ASTM D6751 and EN 14214 due to its high content of monounsaturated fatty esters. Also explored were the properties of blends of HME, PME and WME in ultra-low sulfur (<15ppm) diesel (ULSD) fuel and comparison to petrodiesel standards ASTM D975, D7467 and EN 590. With increasing content of biodiesel, the oxidative stability, cold flow properties and calorific value of ULSD was negatively affected, whereas lubricity was markedly improved. Kinematic viscosity, specific gravity and surface tension were impacted to lesser extents by addition of biodiesel to ULSD. In summary, HME, PME and WME are suitable based on their fuel properties as biodiesel fuels and blend components in ULSD.

Volatiles of plums evaluated by HS-SPME with GC–MS at the germplasm level

The volatiles of 75 plums belonging to five species and one interspecific hybrid were investigated by headspace-SPME–GC–MS; 88 volatiles were identified. Prunus salicina and its hybrids had much more compounds and higher contents of volatiles than Prunus domestica and other three Chinese wild species. Aldehydes were the dominant volatiles in P. domestica and Prunus spinosa while esters were the major volatiles in P. salicina, P. salicina hybrids and Prunus ussuriensis fruits. Regarding terpenoids and alcohols, they were relatively high in several P. salicina cultivars, P. salicina hybrids and P. spinosa, and in Prunus cerasifera, respectively. All the plum germplasms could be divided into three groups via principal component analysis: (1) nine cultivars of P. salicina with high ester content, (2) nine Chinese cultivars and one P. salicina hybrid with ester content and two terpenoids, and (3) the rest of the cultivars and three Chinese wild species without characteristic volatiles.

Enzymatic packed-bed reactor integrated with glycerol-separating system for solvent-free production of biodiesel fuel

From the viewpoint of process engineering in enzymatic biodiesel production, this paper provides a practical basis for development of the packed-bed reactor (PBR) on a bench scale. A key component of this work is the separation of glycerol byproduct in continuous operation. To facilitate measuring and separating the byproduct, we constructed the PBR integrated with a glycerol-separating system. Methyl ester content in the effluent increased with increasing pass number of the reaction mixture, whereas the efficiency of glycerol removal was affected significantly by the flow rate in PBR. Further optimization revealed that the PBR could be operated over a long period realizing both a high methyl ester content and an efficient glycerol removal, obtaining a product that meets the biodiesel standard for residual glycerides. To remove soluble glycerol present in the biodiesel, adsorptive purification using ion-exchange resin was applied to the PBR system. The initial glycerol content of approximately 0.053 wt% was reduced to less than 0.003 wt%, which was maintained for more than 140 bed volumes and repeated after regeneration of the resin using methanol. Therefore, this developed model incorporating the enzymatic PBR and glycerol-separating system is promising for practical biodiesel production, in which no wastewater treatment is necessary.

Comparison of Volatile Flavor Components in Four Kinds of Chinese Fermented Black Soybeans (Glycine max (L.) Merrill) by HS-SPME-GC/MS and Chemometrics

The applicability of headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography and mass spectrometry (GC/MS) for determination of volatile flavor components (VFCs) of 4 kinds of Chinese fermented black soybeans (CFBS) collected from 4 different regions of China (Chongqing Yongchuan, Guangdong Yangjiang, Hunan Liuyang and Jiangxi Hukow, respectively). Principal component analysis (PCA) was used to visually compare their VFCs. Sixty-five VFCs were identified from 4 kinds of CFBS. These VFCs were divided into 11 categories including 13 acids, 7 alkenes, 7 alcohols, 6 aldehydes, 10 esters, 1 ether, 3 ketones, 5 phenols, 9 pyrazines,1 sulfide and 3 miscellaneous. In PCA comparison, Chongqing Yongchuan had the highest amount of phenethyl alcohol responsible for intense sauce-like aroma. Guangdong Yangjiang characterized by ginger aroma, was rich in zingiberene. Hunan Liuyang had stronger fatty aroma because of its higher ester content, while Jiangxi Hukow was richer in nutty aroma due to its plentiful pyrazines.

Synthesis of fatty acid methyl ester from used vegetable cooking oil by solid reusable Mg1−x Zn1+xO2 catalyst

Fatty acid methyl ester was produced from used vegetable cooking oil using Mg1−x Zn1+xO2 solid catalyst and the performance monitored in terms of ester content obtained. Used vegetable cooking oil was employed to reduce operation cost of biodiesel. The significant operating parameters which affect the overall yield of the process were studied. The highest ester content, 80%, was achieved with the catalyst during 4h 15min reaction at 188°C with methanol to oil ratio of 9:1 and catalyst loading of 2.55wt% oil. Also, transesterification of virgin oil gave higher yield with the heterogeneous catalyst and showed high selectivity towards ester production. The used vegetable cooking oil did not require any rigorous pretreatment. Catalyst stability was examined and there was no leaching of the active components, and its performance was as good at the fourth as at the first cycle.

Continuous catalyst-free methanolysis and ethanolysis of soybean oil under supercritical alcohol/water mixtures

This work investigates and compares the reaction performance of soybean oil transesterification under supercritical methanol and ethanol, in a continuous catalyst-free process, as a cleaner alternative to conventional chemically catalyzed process. Reactions were performed in a tubular reactor, at 20 MPa, with oil to alcohol ratio of 1:40, varying the temperature in the range from 250 °C to 350 °C, and at two levels of water concentrations, 0 and 10 wt%. Although both processes proceeded with a relatively high reaction rate, conversion achieved by methanolysis was higher than that obtained by ethanolysis. Water positively affected both process: higher ester content and triacylglycerols depletion occurred when 10 wt% water was used compared with anhydrous conditions. Temperature increase favored the conversion of soybean oil to the corresponding methyl or ethyl esters, although temperatures above 300 °C increased the fatty acid degradation degree, a phenomenon responsible for the low ester contents obtained at the highest temperatures and lowest flow rates studied.

Influence of indigenous yeasts on the fermentation and volatile profile of plum brandies

The aim of this study was to determine the influence of different yeasts isolated from fresh blue plum fruits ( Aureobasidium sp.) and spontaneously fermenting plum musts ( Kloeckera apiculata and Saccharomyces cerevisiae), as well as commercial wine and distillery strains, on the fermentation and chemical composition of plum brandies. Gas chromatography methods were used to detect major volatile components. The most rapid fermentation occurred in musts inoculated with S. cerevisiae. However, the highest concentration of ethanol was detected in samples after spontaneous fermentation (8.40% v/v). Plum brandies obtained after distillation contained from 66.3 ( K. apiculata) up to 74.3% v/v ethanol (spontaneous fermentation). The samples after spontaneous fermentation were distinguished by a high content of acetoin, ethyl acetate and total esters, accompanied by a low level of methanol and fusel alcohols. Non- Saccharomyces yeasts were responsible for higher concentrations of esters and methanol, while S. cerevisiae strains resulted in increased levels of higher alcohols. It was also found that isolated indigenous strains of S. cerevisiae synthesized relatively low amounts of higher alcohols compared to commercial cultures. Samples obtained using the distillery strain of S. cerevisiae received the highest score (18.2) during sensory analysis and were characterized by a well-harmonised taste and aroma.

Rapid transesterification of soybean oil with phase transfer catalysts

Biodiesel is a renewable, non-toxic and biodegradable alternative fuel for compression ignition engines. Biodiesel is produced mainly through base-catalyzed transesterification of animal fats or vegetable oils. However, the conventional base-catalyzed transesterification is characterized by slow reaction rates at both initial and final reaction stages limited by mass transfer between polar methanol/glycerol phase and non-polar oil phase. In our study we used phase transfer catalysts (PTCs) to facilitate anion transfer between polar methanol/glycerol phase and non-polar oil phase to speed up transesterification. The benefits of transesterification by PTCs include no need for expensive aprotic solvents, potentially simpler scaleup and higher activity (shorter reaction time). Various PTCs were investigated for base-catalyzed transesterification. Experimental results showed that base-catalyzed transesterification was enhanced with an effective PTC, indicated by the formation of high methyl ester (ME) content within a relatively short time. Individual operating variables such as molar ratios of methanol to oil, total OH − to oil, PTC to base catalyst and agitation including ultrasound were investigated for transesterification with PTC. Product analyses showed that ME content higher than 96.5 wt.% was achieved after only 15 min of rapid transesterification with PTC (tetrabutylammonium hydroxide or tetrabutylammonium acetate as PTC, MeOH/oil molar ratio of 6, total OH −/oil molar ratio of 0.22, PTC/KOH molar ratio of 1 and 60 °C). Free and total glycerol contents in the final product from 15 min rapid transesterification with PTC were lower than maximum allowable limits in the standard specification for biodiesel.

Media Formulation using Complex Organic Nutrients for Improved Activity, Productivity, and Yield of Candida rugosa Lipase and Esterase Enzymes

Candida rugosa is an excellent source of multiple lipase and esterase enzymes; therefore, it is of technological importance to formulate the medium that provides high activity for each enzyme. In this work, the cultivation medium comprising complex nutrients that provided the highest activity, productivity, and yield of C. rugosa enzymes individually was formulated. Time courses of the extracellular and intracellular lipase and esterase activities of C. rugosa were represented and the role of protease in the cultivation progress was discussed. Urea, soy-peptone, yeast extract, a mixture of soy-peptone and yeast extract, cheese whey, and wheat mill bran were tested for their lipolytic and esterasic activities. Urea provided considerably higher extracellular lipase activity when compared to other nitrogen sources; however, soy-peptone provided the highest extracellular esterase activity. Hazelnut, olive, sesame, soybean, and flax seed oils affected the enzyme activities to different extents related to their fatty acid compositions. Hazelnut oil and olive oil provided the highest extracellular lipase and esterase activities, respectively, whereas sesame oil produced the highest biomass. High C18 and C16 ester contents of vegetable oils promoted high lipase and esterase productions, respectively. A temperature of 30°C yielded the highest extracellular and intracellular lipase and esterase activities; however, 35°C produced the highest biomass.

A comparative study of biochemical traits and molecular markers for assessment of genetic relationships between Jatropha curcas L. germplasm from different countries

Jatropha curcas has gained popularity as a potential biofuel crop but the major constraint for improvement of the crop for yield and seed quality traits is the narrow genetic base of the germplasm. Genetic background of 72 J. curcas accessions representing 13 countries has been elucidated using molecular analysis and biochemical traits. Seed kernel protein, oil content, ash content and phorbol esters revealed variation with accessions from Mexico containing low levels of phorbol esters. Molecular characterization disclosed polymorphism of 61.8 and 35.5% with RAPD and ISSR primers, respectively and Mantel test revealed positive correlation between the two marker systems. Dendrogram based on pairwise genetic similarities and three-dimensional principal coordinate analysis using data from RAPD and ISSR marker systems showed close clustering of accessions from all countries and grouped the Mexican accessions separately in clusters III, IV, V and VI. Presence of the toxic phorbol esters is a major concern and analysis of 28 Mexican accessions resulted in identification of molecular markers associated with high and low phorbol ester content. The identified RAPD and ISSR markers were converted to SCARs for increasing the reliability and use in marker assisted programmes aimed at development of accessions with reduced toxicity. Twelve microsatellite primers differentiated the non-toxic Mexican accessions and disclosed novel alleles in Mexican germplasm. Amplification with primers specific to the curcin coding sequence and promoter region of ribosome-inactivating protein (RIP) revealed polymorphism with one primer specific to RIP promoter region specifically in accessions with low phorbol ester levels. Narrow genetic variation among accessions from different regions of the world and rich diversity among Mexican genotypes in terms of phorbol ester content and distinct molecular profiles indicates the need for exploitation of germplasm from Mexico in J. curcas breeding programmes.

Effect of nitrogen fertilization on quality markers of strawberry (Fragaria × ananassa Duch. cv. Aromas)

AbstractBACKGROUND: Nitrogen is an indispensable element for fruit metabolism and low or excessive N levels can affect the accumulation of the most important components that contribute to the flavour and aroma of the fruit. Among them, sugars, acids and volatile compounds can be considered quality markers. The objective of this study was to evaluate the effect of N fertilization on these quality markers of the fruit at two harvest dates.RESULTS: Strawberry plants were grown in a hydroponic system and N was applied as Ca(NO3)2 at concentrations of 0.3, 3 and 6 mmol L−1 in the nutrient solution. Total soluble solids, soluble carbohydrates, amino acids and organic acids and volatile compounds of the fruit were analyzed. The fruits produced at 3 and 6 mmol L−1 N had higher contents of esters, soluble carbohydrates and amino acids. The hexanal content increased with the 6 mmol L−1 dose. The effect of fertilization was more marked at the second harvest date.CONCLUSION: The availability of N in strawberry plants affected the accumulation of quality markers. The fruits expected to have the best flavour and aroma, with both high levels of soluble carbohydrate and esters and low levels of hexanal, were obtained with 3 mmol L−1 nitrate in the solution. Copyright © 2009 Society of Chemical Industry