Search results for "Esteri"
showing 10 items of 220 documents
Interesterification of rapeseed oil catalyzed by tin octoate
2014
The interesterification of rapeseed oil was performed for the first time by using tin octoate as Lewis acid homogeneous catalysts and methyl or ethyl acetate as acyl acceptors in a batch reactor, within the temperature range 393–483 K. The yields in fatty acid ethyl esters (FAEE) and triacetin (TA) after 20 h of reaction time increased from 8% and 2%–to 61% and 22%, respectively, when the reaction temperature increased from 423 to 483 K. An optimum value of 40 for the acyl acceptor to oil molar ratio was found to be necessary to match good fatty acid alkyl ester yields with high enough reaction rate. The rate of generation of esters was significantly higher when methyl acetate was used as a…
A thermo-alkaline lipase from a new thermophileGeobacillus thermodenitrificansAV-5 with potential application in biodiesel production
2015
BACKGROUND A thermophilic lipase-producing Geobacillus thermodenitrificans strain AV-5 was isolated from the Mushroom Spring of Yellowstone National Park in WY, USA and studied as a source of lipase for transesterification of vegetable oils to biodiesel. RESULTS A maximum activity of 330 U mL−1 was produced on 2% (v/v) waste cooking oil at 50 °C, pH 8, aeration rate of 1 vvm and agitation speed of 400 rpm. However, the higher lipase productivity (14.04 U mL−1 h−1) was found at a volumetric oxygen transfer coefficient (kLa) value of 18.48 h−1. The partially purified lipase had a molecular weight, temperature and pH optimum of 50 kDa, 65 °C and pH 9, respectively, and was thermo-alkali stable…
Hepatic and very low-density lipoprotein fatty acids in obese offspring of overfed dams.
2010
The combined effects of developmental programming and high-fat feeding at weaning on fatty acid metabolism of the offspring are not well known. In the present study, we aim at characterizing the influence of maternal and offspring's own diets on liver and very low-density lipoprotein (VLDL) lipids; fatty acid profiles of VLDL and liver phospholipids, triglycerides, and cholesteryl esters; and hepatic enzyme activities. Twenty obese male rats born to cafeteria diet-fed dams and 20 control rats born to control diet-fed dams were selected. At weaning, 10 rats of each group were fed control or cafeteria diet. Obese rats had a significant increase in serum glucose, insulin, leptin, VLDL apolipop…
Blood pressure and cardiac autonomic nervous system in obese type 2 diabetic patients: effect of metformin administration
2004
Background: Hyperinsulinemia/insulin resistance and elevated plasma free fatty acids (FFA) levels are involved in the hypertension and cardiac sympathetic overactivity. Metformin improves insulin action and lower plasma FFA concentrations. We investigate the possible effect of metformin on arterial blood pressure (BP) and cardiac sympathetic nervous system. Methods: One hundred twenty overweight type 2 diabetic patients were treated by placebo (n = 60) + diet or metformin (850 mg twice daily) (n = 60) + diet for 4 months, to evaluate the effect of metformin treatment on the cardiac autonomic nervous system. Insulin resistance was measured by the Homeostasis Model Assessment (HOMA) index. He…
The effects of cold and glucagon on lipolysis, glycogenolysis and oxygen consumption in young chicks.
1973
Abstract 1. 1. To study the possible role of glucagon in avian thermoregulation the effects of cold exposure and glucagon on lipolysis, glycogenolysis and oxygen consumption were measured in young chicks. 2. 2. Cold exposure (+10°C) and glucagon injection (0·3 mg/kg, i.p. at +30°C) both caused a marked increase in the plasma FFA and a decrease in the liver glycogen content. 3. 3. It is suggested that glucagon possibly acts in the avian thermoregulation by producing at least lipolysis and glycogenolysis during cold exposure.
Plasma corticosteroids, free fatty acids, insulin and glucose in maternal blood during delivery.
1970
Plasma-corticosteroids (PCS), free fatty acids (FFA), insulin and glucose were determined continously in maternal blood during the entire course of delivery, from the first stage of labour until 6 hours after delivery. A steep increase in the PCS and FFA concentration could be noticed from the onset of labour (PCS: 37,8±11.2 µg/100 ml;\(s_{\bar x} \),p≦0.01; FFA: 556±106.6 µVal/l;\(s_{\bar x} \),p≦0.01) to the birth of the child (PCS: 96.8±19,5 µg/100 ml;\(s_{\bar x} \),p≦0.01; FFA: 1129±220 µVal/l;\(s_{\bar x} \),p≦0.01) and basal levels were already reached 6 hours later (PCS: 36.0±18.5 µg/100 ml;\(s_{\bar x} \),p≦0.01; FFA: 538±192.8 µVal/l;\(s_{\bar x} \),p≦0.01). The rise of insulin an…
Direct HPLC Monitoring of Lipase Activity in Reverse Micellar Media
1995
Given the profusion of biotechnological applications of the nonaqueous use of lipases, we have evaluated the possibilities of exploiting the inherent advantages of high performance liquid chromatography (HPLC) for a simple, rapid assay of lipase activity in reverse micellar media, as a convenient alternative to previously reported spectroscopic methods, using both a model system and esterification reaction, and different commercial lipases. The results obtained after a screening for optimized chromatographic conditions in the reverse-phase mode indicate that a satisfactory resolution of the reaction components can be obtained following a straightforward protocol, which permits an accurate, …
Hypersusceptibility of neutrophil granulocytes towards lethal action of free fatty acids contained in enzyme-modified atherogenic low density lipopro…
2008
Abstract Objective The bulk of LDL entrapped in the arterial intima is modified by hydrolytic enzymes, leading to extensive cleavage of cholesterylesters and liberation of fatty acids. The latter induce apoptosis in endothelial cells but are far less cytotoxic towards macrophages. We have compared the cytotoxic effects of enzymatically modified LDL (E-LDL) on macrophages and polymorphonuclear granulocytes (PMN). Methods and results E-LDL displayed toxicity towards PMN at far lower concentrations than towards monocyte-derived macrophages. Native or oxidized LDL had no effect. Free fatty acids contained in E-LDL were the cause of the observed toxicity, which could be mimicked by linoleic acid…
Design of enzyme-mediated controlled release systems based on silica mesoporous supports capped with ester-glycol groups
2012
[EN] An ethylene glycol-capped hybrid material for the controlled release of molecules in the presence of esterase enzyme has been prepared. The final organic-inorganic hybrid solid S1 was synthesized by a two-step procedure. In the first step, the pores of an inorganic MCM-41 support (in the form of nanoparticles) were loaded with [Ru(bipy) 3]Cl 2 complex, and then, in the second step, the pore outlets were functionalized with ester glycol moieties that acted as molecular caps. In the absence of an enzyme, release of the complex from aqueous suspensions of S1 at pH 8.0 is inhibited due to the steric hindrance imposed by the bulky ester glycol moieties. Upon addition of esterase enzyme, del…
Influence of lipid physical state on the in vitro digestibility of emulsified lipids.
2008
The objective of this study was to investigate the influence of the physical state of emulsified lipids on their in vitro digestibility by pancreatic lipase. A 10 wt % tripalmitin oil-in-water emulsion stabilized by sodium dodecyl sulfate (0.9 wt % SDS) was prepared at a temperature (>70 degrees C) above the melting point of the lipid phase (T(m) approximately 60 degrees C). A portion of this emulsion was cooled to a temperature (0 degrees C for 15 min) well below the crystallization temperature of the emulsified lipid (T(c) approximately 22 degrees C) and then warmed to 37 degrees C so as to have completely solid lipid particles. Another portion of the emulsion was directly cooled from 70 …