Multiple response optimization of vegetable oils fatty acid composition to improve biodiesel physical properties

The effect of fatty acids chain length (LC) and its interaction with unsaturation degree (UD) on important biodiesel quality parameters was studied. Low calorific value, kinematic viscosity, flash point, cetane number and cold filter plugging point of biodiesel blends covering a wide range of fatty acids were analyzed. Analytical results were processed with statistical regression to obtain a prediction model for each property, combining LC and UD. Due to the antagonistic effects of the chemical composition over quality properties, the Derringer desirability function was proposed to allow the most suitable fatty acid composition. This target was achieved considering an average of 1.26 double bounds and 17 carbon atoms. A set of combinations of LC and UD values that provides a biodiesel that fits the European standard EN 14214 was proposed. It was found that a reduction of FAME LC allows a lower UD while keeping biodiesel specifications under the standard limits.     

Microalgal fatty acid composition: implications for biodiesel quality

The fuel properties of microalgal biodiesel are predicted using published microalgal fatty acid (FA) compositions and predictive fuel models. Biodiesels produced from the microalgae investigated are predicted to have extremely poor oxidative stabilities and the majority also have poor cold-flow properties. The cetane number in most cases is out of specification, but less so than the oxidative stability and cold flow. These findings support the idea that feedstocks rich in monounsaturated fatty acids (MUFAs) are desirable for biodiesel but the composition of the saturated fatty acids (SFAs) is also shown to be of great importance. There is an apparent relationship between algal class and the percentage of FAs represented by MUFA. This potentially allows for the identification of high-MUFA algal classes, or at least provides some basis for researchers to make initial selections of target classes for bioprospecting. Comparisons of FA groups between algal classes also show that the SFAs of Mediophyceae contain significantly higher proportions of C14:0, which is in contrast to the normally abundant C16:0 and the Mediophyceae therefore have better cold-flow characteristics than other classes with similar total SFA contents. Certain particularly promising cases for biodiesel production are presented as species level examples of feedstocks that are close to satisfying the biodiesel standards and to further illustrate the challenges that remain. Variation in FA composition as a response to changes in certain environmental variables forms another important facet to feedstock selection and is briefly considered, with suggestions for further research.     

Characterization of the fatty acid composition of Nannochloropsis salina as a determinant of biodiesel properties

Nannochloropsis salina was cultured batch-wise to evaluate the potential of the alga to produce biodiesel. The cells were harvested at the end of the exponential growth phase when the concentration was 18 x 10(6) cells/mL culture. The growth estimated as dry weight from this cell number was (3.8 +/- 0.7) mg/L. The lipid and triglyceride contents were 40% and 12% on a dry weight basis, respectively. The amount of the ratio triglycerides/total lipids was approximately 0.3. The composition of triglyceride fatty acid methyl esters (biodiesel) was analysed by gas-liquid chromatography and identified as: C14:0, C16:0, C16:1, C18:0, C18:1, C18:2, C18:3, C20:1, and C20:5. The ratio of unsaturated to saturated fatty acid contents was approximately 4.4. Additionally, the characterization of each individual fatty acid ester was discussed with regard to the fuel properties of biodiesel produced by the alga.     

Influence of vegetable oils fatty acid composition on reaction temperature and glycerides conversion to biodiesel during transesterification

Presence of unreacted glycerides in biodiesel may reduce drastically its quality. This is why conversion of raw material in biodiesel through transesterification needs to readjust reaction parameter values to complete. In the present work, monitoring of glycerides transformation in biodiesel during the transesterification of vegetable oils was carried out. To check the influence of the chemical composition on glycerides conversion, selected vegetable oils covered a wide range of fatty acid composition. Reactions were carried out under alkali-transesterification in the presence of methanol. In addition, a multiple regression model was proposed. Results showed that kinetics depends on chemical and physical properties of the oils. It was found that the optimal reaction temperature depends on both length and unsaturation degree of vegetable oils fatty acid chains. Vegetable oils with higher degree of unsaturation exhibit faster monoglycerides conversion to biodiesel. It can be concluded that fatty acid composition influences reaction parameters and glycerides conversion, hence biodiesel yield and economic viability.     

Membrane fatty acid composition and endothelial cell functional properties

In order to study the influence of endothelial cell fatty acid composition on various membrane related parameters, several in vitro methods were developed for manipulating the fatty acid content of human endothelial cell membranes. Changes in membrane fatty acid profile were induced by using fatty acid modified lipoproteins or free fatty acids. The largest changes in endothelial fatty acid composition were obtained by culturing the cells in media supplemented with specific free fatty acids. An increase in arachidonic acid content of endothelial phospholipids was induced by supplementation with saturated fatty acids or with arachidonic acid itself. A decrease in arachidonic acid content was obtained by supplementation with other unsaturated fatty acids. Under the experimental conditions used endothelial cells showed a low desaturase activity and a high elongase activity. Considerable alterations in membrane fatty acid composition did not greatly influence certain membrane related parameters such as polymorphonuclear leukocyte adherence and endothelial cell procoagulant activity. In general, for fatty acid modified endothelial cells an association between endogenous arachidonic acid content and total production of eicosanoids was found. This study demonstrates that considerable changes in membrane fatty acid profile affect endothelial cell arachidonic acid metabolism, but it also illustrates homeostasis at the level of endothelial cell functional activity.     

Influence of ethanol on fatty acid composition of phospholipids in cultured neurons

Animals chronically exposed to ethanol show changes in neural membrane lipids which may underlie the development of tolerance and physical dependence. The object of this study was to investigate changes in the fatty acid composition of neuronal phospholipids cultured in the presence of ethanol (55 or 110 mM) for periods up to 7 days. Decreases were observed in the percentage of individual and total saturated fatty acids, while the double bond index: total saturated fatty acid ratio, increased. These changes do not support the hypothesis that neural membrane lipid composition changes to counteract the fluidizing action of ethanol.     

Influence of vegetable oils fatty-acid composition on biodiesel optimization

Biodiesel is an alternative fuel for diesel engines produced through transesterification of oleaginous feedstocks. To analyze the influence of the fatty-acid composition on biodiesel optimization, transesterification of several vegetable oils has been studied. Reactions were carried out in flasks filled with vegetable oils, heated to the reaction temperature and stirred at 1100 rpm. The reactions started when the methanol and potassium hydroxide solutions were added to the flasks. Concentration of catalyst, amount of methanol, reaction temperature and time were optimized using a factorial design and a surface response design. Also, a kinetics study was carried out to optimize the reaction time. Results showed that reaction parameters optimal values depend on the oil chemical and physical properties. It can be concluded from this field trial that the effect of both catalyst concentration and reaction time over the transesterification yield is greatly influenced by the saturation degree and fatty-acid chain length.     

The effect of temperature on growth and lipid and fatty acid composition on marine microalgae used for biodiesel production

Cultivation temperature is one of the major factors affecting the growth and lipid accumulation of microalgae. In this study, the effects of temperature on the growth, lipid content, fatty acid composition and biodiesel properties of the marine microalgae Chaetoceros sp. FIKU035, Tetraselmis suecica FIKU032 and Nannochloropsis sp. FIKU036 were investigated. These species were cultured at different temperatures (25, 30, 35 and 40 °C). The results showed that the specific growth rate, biomass and lipid content of all microalgae decreased with increasing temperature. With regards to fatty acids, the presence of saturated fatty acids (SFAs) in T. suecica FIKU032 and Nannochloropsis sp. FIKU036 decreased with increasing temperature, in contrast with polyunsaturated fatty acids (PUFAs). Moreover, Chaetoceros sp. FIKU035 was the only species that could grow at 40 °C. The highest lipid productivity was observed in Chaetoceros sp. FIKU035 when cultivated at 25 °C (66.73 ± 1.34 mg L^?1 day^?1) and 30 °C (61.35 ± 2.89 mg L^?1 day^?1). Moreover, the biodiesel properties (cetane number, cold filter plugging point, kinematic viscosity and density) of the lipids obtained from this species were in accordance with biodiesel standards. This study indicated that Chaetoceros sp. FIKU035 can be considered as a suitable species for biodiesel production in outdoor cultivation.     

Oil content,fatty acid composition and biodiesel properties among natural provenances of Siberian apricot (Prunus sibirica L.) from China

Siberian apricot (Prunus sibirica L.), an excellent woody oil plant unique to Asia, is well known for its ability to produce high‐oil seeds for use as a promising feedstock of biodiesel. Based on the investigation of natural Siberian apricot resources in China in the early stage, seeds of Siberian apricot from 74 geographic provenances which can fully reflect the overall information were collected. In this research, seeds oil content, fatty acid composition and biodiesel properties were evaluated, and the key environmental factors that caused the variation of these in different geographic provenance were analyzed. The oil content of Siberian apricot seeds is 45.48%–61.07%, and the average was 50.95% for all provenances. The characteristics of oil can identify and quantify eight fatty acids. The most abundant fatty acids were oleic acid (C18:1; 54.02%–76.54%), followed by linoleic acid (C18:2; 16.78%–38.49%) and erucic acid (C16:0; from 3.27% to 6.12%). Monounsaturated fatty acids are the most abundant in 54.75%–77.03% compared with saturated fatty acids and polyunsaturated fatty acids. The biodiesel properties of most provenance seeds meet the standards of the ASTM D6751 and GB/T 20828, and a few meet the standards of the EN14214. Through the clustering of oil content and fatty acid composition and the analysis of biodiesel properties indexes, it is concluded that KSK provenance is the most suitable for biodiesel production. The XBZ, HHE, AES, ZLQ and LD provenances may be preserved as potential biodiesel. RDA and VPA showed that the effects of environmental factors on the oil properties of Siberian apricot were ranked as terrain factor > climate factor > soil factor, among which longitude, latitude and altitude are the main terrain indicators. These evaluations can provide reference for the effective utilization and further development of Siberian apricot as a bioenergy feedstock.     

Influence of growth conditions on fatty acid composition of a polyunsaturated-fatty-acid-producing Vibrio species

The influence on fatty acid composition of growth medium composition and phase of growth during batch culture and of dilution rate and growth temperature during continuous culture was studied in the eicosapentaenoic-acid (20:5 n-3)-producing Vibrio CCUG 35308. In glucose-mineral medium, even-numbered normal fatty acyl residues, primarily 16:0, 16:1, 18:1, and 20:5, strongly dominated (ca. 90%), and the fatty acid profile remained practically unchanged throughout a batch-growth cycle. In nutrient broth, the contribution by “uncommon” fatty acids, mainly i-13:0, 15:0, i-15:0, and 17:1 was generally higher, and increased from 15.4% of total fatty acids in early exponential growth phase to 33.2% in the stationary phase. Reduction of the dilution rate in a chemostat from 0.27 to 0.065 h^–1 also led to an almost threefold increase in the proportion of odd-numbered residues at the expense of the even-numbered normal ones. Contrary to this plasticity in the overall fatty acid profile influenced by variations in nutrient composition and availability, the level of eicosapentaenoic acid seemed exclusively dictated by growth temperature. The synthesis of this polyunsaturated fatty acid may be a key regulatory process in maintaining membrane fluidity. Received: 3 November 1995 / Accepted: 25 February 1996     

Influence of ethanol on the lipid content and fatty acid composition ofSaccharomyces cerevisiœ

The content of total lipid as well as of ergosterol, squalene, and major fatty acids were compared in the cells of a distillery strain ofSaccharomyces cerevisiœ incubated for 3, 48 and 120 h in the presence of 5, 10 and 15% ethanol. Ethanol induced lipid accumulation with preferential ergosterol biosynthesis. The relative contents of palmitic and stearic acid decreased whereas the amount of palmitoleic and oleic acid increased. The total content of all fatty acids rose as a consequence of the ethanol treatment.     

Influence of a long-term zinc-deficient diet on rat platelet function and fatty acid composition

A reduced zinc intake is associated with numerous abnormalities and, in particular, with hemostasis dysfunction. In this report, we studied the effects of a long-term dietary zinc restriction on platelet function. Three groups of rats were analyzed: a zinc-deficient group (ZD) and two zinc-adequate fed groups, one pair-fed (PF) and one ad libitum fed (AL). We found that ZD diet (0.2 p.p.m.) impaired ADP-induced aggregation of washed platelet after 4 and 8 weeks of diet. Thrombin-induced aggregation was impaired in ZD rats and PF rats after 8 weeks. The thrombin-induced mobilization of radiolabeled arachidonate preincorporated into platelet phospholipids was followed as well as the subsequent formation of labeled cyclooxygenase and lipoxygenase products. Stimulated platelets of ZD rats exhibited a decreased production of cyclooxygenase and lipoxygenase products, particularly after 8 weeks of diet. Moreover, platelet thromboxane generation was decreased in the ZD group as studied using a radioimmunoassay after thrombin stimulation. In addition, we measured the total fatty acid compositions of platelet and plasma. As a whole, 20:5 (n – 3) and 22:5 (n – 3) fatty acids content were significantly increased in platelet lipids after 8 weeks. On the other hand, it is known that enrichment of these fatty acids through dietary studies, both in animal and human as well as in vitro incorporation in platelets, resulted in an inhibition of platelet function. Consequently, these changes in platelet membrane fatty acid composition may contribute to the impaired platelet aggregation observed in ZD rats.     

An effective acid catalyst for biodiesel production from impure raw feedstocks

Biodiesel consists of fatty acids short chain alkyl esters produced through transesterification and esterification of fats and oils. Production of biodiesel is strongly affected by the purity of raw lipids, and catalysts play important role in these processes. Although direct utilization of impure feedstocks is more economical, their use necessitates development of effective catalysts to overcome hindering influences of impurities. In this study, sulfuryl chloride, thionyl chloride, acetyl chloride, p-toluenesulfonic acid, benzenesulfonic acid, methanesulfonic acid, dimethylsulfate and sulfuric acid were investigated as catalysts for the production of biodiesel because acids have higher tolerance to water and free fatty acids in oils and can simultaneously catalyze both the esterification and transesterification reactions. Sulfuryl chloride was found to be an effective catalyst for production of biodiesel from soybean oil, its waste oil and microalgal lipids.     

Influence of methylfenpropidine on growth, sterol content and fatty acid composition ofCandida albicans

The effect of methylfenpropidine on growth, lipid contents, sterol and fatty acid composition was investigated in 5 strains ofCandida albicans. The sensitivity of the strains decreased in the order: wild strains >erg ⁺ ade nys ^R >ade nys ^R erg (defective Δ⁸⁻⁷-isomerase) >ade nys ^R erg (defective Δ⁵-desaturase). The presence of the inhibitor influenced fecosterol isomerization, episterol dehydrogenation, zymosterol transmethylation, ignosterol reduction and squalene epoxidation. Methylfenpropidine also induced changes in fatty acid composition, causing a reduction of the palmitic and oleic acid content with a concomitant elevation of stearic, linoleic and linolenic acid levels. The lipid unsaturation index slightly increased. Morphological changes of wild strains were observed after the fungicide treatment.     

Influence of different co-substrates biochemical composition on raw sludge co-composting

The influence of biochemical composition of different co-substrates added to raw sludge during co-composting process was studied. The physical properties of the composting mass and their influence on the biological activity were also investigated. Three treatments composed of mixtures of raw sludge and co-substrate (commercial fats, protein, and cellulose) were carried out and compared to a control composed of raw sludge. Mixture conditioning was performed on the basis on air filled porosity (40%). The results obtained in the co-composting processes reflected a higher biological activity and higher degradation percentages of dry and organic matter when compared with control. Higher temperatures (60, 67 and 62°C for fats, protein and cellulose, respectively) were also achieved in all co-composting experiments as compared to the control test (55°C). Biological activity was measured using both Static and Dynamic Respiration Indices obtaining higher values in co-composting experiments compared to the control test. Fats content reduction was higher (66%) at higher fats content in the initial mixture (10.6%). The addition of fats seems also to promote the degradation of cellulose and lignin. Co-composting experiments with fats and cellulose presented higher initial C/N ratio and lower nitrogen losses, 27.5 and 34.2% compared to 40% for raw sludge. It has been demonstrated that the addition of an adequate co-substrate to raw sludge leads to a higher degradation percentages of the different biochemical fractions and higher nitrogen conservation.     

Engineering fatty acid biosynthesis in microalgae for sustainable biodiesel

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Higher fatty acid composition of enterococci

The content of unsaturated fatty acids in enterococcal cells has been found to have no essential relation to the composition of the culture medium. When cultivated in the same media, S. faecium had the degree of lipid unsaturation 1.5-2 times higher than S. faecalis. Mobile enterococci are sharply differentiated from immobile species by the content of cyclopropanic acid with 19 carbon atoms, constitute a heterogenous group and consist of at least 2 taxons, differing in the content of acids with 18 carbon atoms and the degree of lipid unsaturation.