Esterification of exogenous and endogenous fatty acids by rat adipocytes in vitro.

Rat adipocytes were used in vivo to compare the esterification of exogenous fatty acids and fatty acids formed de novo from glucose or acetate. Pure single fatty acids added to the medium were esterified at comparable rates but marked differences were observed when the same acids were supplied as components of a fatty acid mixture of a composition similar to that in the tissue. Fatty acids synthesised de novo from acetate by adipocytes in a medium containing high concentrations of acetate were located predominantly in diacylglycerols. The effect was most marked with adipocytes from older rats and was enhanced by the presence of exogenous long-chain fatty acids. Exogenous oleic acid was esterified predominantly into triacylglycerols at all concentrations of acetate. No such accumulation of endogenously-synthesised fatty acids in diacylglycerols occurred when glucose was the precursor for fatty acid synthesis. The diacylglycerols formed were almost entirely of the sn-1,2-configuration.     

Stimulation of oxidation of mitochondrial fatty acids and of acetate by acetylcarnitine

1. Acetylcarnitine added in catalytic amounts to kidney mitochondria produces an active oxidation of endogenous fatty acids. 2. In conditions of mitochondrial ;aging', under which acetate is not oxidized, acetylcarnitine also promotes the oxidation of this exogenous substrate. 3. Dinitrophenol completely abolishes the action of acetylcarnitine. 4. Carnitine is ineffective both in the oxidation of endogenous fatty acids and of exogenous acetate. 5. The action of acetylcarnitine is shared, though to a smaller extent, by pyruvate. 6. The mechanism of acetylcarnitine action has been interpreted by considering that the readily oxidizable acetyl group of acetylcarnitine can supply the initial investment of energy needed to start fatty acid oxidation.     

Esterification of fatty acids using Candida antarctica lipase A in water-abundant systems

The feasibility of using native lipase A from Candida antarctica (CAL-A) to esterify fatty acids with water-insoluble alcohols in the presence of excess water was investigated in stirred-tank reactors. For high reaction rates, a ratio of water:substrates of 0.6-1.4:1 (v/v) was required. CAL-A showed higher substrate selectivity for the esterification of saturated palmitic acid with branched-chain 2-ethyl-1-hexanol than for unsaturated oleic acid with linear alcohol (1-decanol). After 18 h at 70 °C in a 1.5 l bulk stirred-tank reactor, an 2-ethyl-1-hexyl palmitic acid ester was obtained near 100 % yield [molar ratio palmitic acid:2-ethyl-1-hexanol ~1:1.25, with 1.11 % (w/w) Novocor ADL (based on palmitic acid weight)].     

Formation of hypsorhodopsin at room temperature by picosecond green pulse

Excitation of squid rhodopsin with a single laser pulse (532 nm, 25 ps) at 18 degrees C yielded photorhodopsin, a precursor of bathorhodopsin. In the linear region, no relation between amount of photorhodopsin and excitation-energy hypsorhodopsin was detected, while in a photon saturation region this was observed. The time constant of hypsorhodopsin to bathorhodopsin decay was about 125 ps. Dependencies of formation of photorhodopsin and hypsorhodopsin on the excitation energy suggest that hypsorhodopsins of squid and octopus are formed by a two-photon reaction. No cattle hypsorhodopsin was detected in our experimental conditions.     

Esterification using a liquid lipase to remove residual free fatty acids in biodiesel

Lately, the price of liquid formulated lipase enzymes, usable in biodiesel production, has been significantly reduced. This enables one-time use of these enzymes for transesterification, and the process is used industrially. However, the process suffers a drawback by leaving 2−3 % free fatty acids in the crude biodiesel, which reduces the profitability. This article discusses a novel enzymatic FFA esterification reaction utilizing liquid lipase B from Candida antarctica (CALB) along with glycerol at low water concentrations to eliminate the residual FFA. The reaction setup was found able to reduce the free fatty acid concentration to within biodiesel specifications of < 0.25 wt.% FFA. Additionally, two alternative process setups are proposed, which were both found viable through a combination of experiments and simulations, and can be developed into full-scale processes. The resulting two-step enzymatic biodiesel process - transesterification followed by esterification - provides a potential process layout for the industrial production of biodiesel.     

Preparation of dry reconstituted liposomal powder by freeze-drying at room temperature

The aim of this study was to develop a novel, one-step method of liposome preparation by freeze-drying at room temperature as well as to investigate the physicochemical properties of dry reconstituted liposomal powder that was prepared. The method was based on utilizing sublimation of a volatile solid inert carrier, that is, chlorobutanol hemihydrate (CBN), instead of ice, which was less sophisticated and simpler than the conventional freeze-drying process. The optimum conditions used in the sublimation process of CBN were a temperature of 25–30°C and a pressure of 1.5–2.0 mBar for 8 hours. The influence of various parameters, such as type, particle size, and ratio of sugar lyoprotectant (i.e., mannitol or sucrose) and CBN to lipid on reconstitution time, liposome size, zeta potential, vesicle type, and lamella structure of reconstituted liposomes, were studied. The results revealed that the obtained liposomes were oligolamellar vesicles with particle sizes ranging from 400 to 1,000?nm. Type and ratio of sugar and CBN to lipid were found to significantly affect the reconstitution time. On the other hand, liposome size was independent of type of sugar and ratio of CBN to lipid, yet became smaller at higher sugar-to-lipid ratio and smaller sugar and CBN size. In all cases, traces of residual solvents were definitely below the acceptable limit.