Selective production of emulsifiers from glucose and fatty acids has been achieved using an immobilized Candida antarctica lipase. Optimization of process selectivity considers the solubilities of the sugar and its monoesters in acetone at different temperatures, the percentage of this organic solvent in the reaction mixture, and the reaction temperature. The solvent (acetone) is both easily eliminated and accepted by the European Community for use in the manufacture of foods and/or food additives. Different fatty acids with a longer length chain than that of caprylic acid may be employed. For saturated fatty acids longer than lauric acid, continuous precipitation of the monoester as it is formed at 40°C permits nearly complete conversion (98%) of glucose to the monoester within 2–3 days. The procedure does not require total dissolution of the sugar, and precipitation of the monoester permits selective conversion of charges of glucose higher than 100 mg/mL solvent. A scaleup of the process under the optimum conditions gives high yields of 6‐O‐lauroyl glucose, which may be readily prepared on a gram scale. ©1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 505‐509, 1998.
A simple kinetic model derived from a ping-pong bi-bi mechanism is proposed to describe the lipase-catalyzed esterification of glucose with fatty acids. The mathematical expressions derived from this model have been tested using several sets of data obtained from reactions carried out under different reaction conditions. The predicted values provide very good fits of the experimental data for temperatures from 30 to 60 degrees C, enzyme loadings from 90 to 180 mg, and fatty acid concentrations from 0.33M to 1M. Experiments conducted at different temperatures permit one to estimate an activation energy of approximately 12 kcal/mol for the rate-limiting step of the reaction (formation of the acyl-enzyme complex). The model also considers the kinetics of inactivation of the biocatalyst during the reaction.
A new method for regioselective analysis of triacylglycerols via conventional high-performance liquid chromatography (HPLC) has been developed. The method is simple and avoids the time-consuming purification processes normally characteristic of regioselective analyses. The procedure utilizes an sn-1,3-specific lipase from Rhizopus arrhizus to deacylate the fatty acid residues located at the sn-1 and sn-3 positions of triacylglycerols. The fatty acid residues esterified at the sn-2 position are determined by subtraction of the results of the sn-1,3 analysis from an overall composition analysis based on complete saponification of the original sample. The fatty acid mixtures are converted to p-bromophenacyl esters and analyzed using conventional HPLC techniques. The analytical procedure has been verified using a standard structured triacylglycerol. The analytical results for three edible vegetable oils are compared with those obtained via the method proposed by P.J. Williams and co-workers.A substantial body of scientific evidence indicates that ingestion of specific types of fats and oils is implicated in the development of coronary heart disease. Similarly, there is increasing scientific evidence that ingestion of particular fatty acids (e.g., ω-3 fatty acids and conjugated linoleic acid) leads to reduced incidence of certain diseases (e.g., atherosclerosis and particular forms of cancer). In addition to the degree of saturation of the fatty acid residues, the positions of specific fatty acid residues in the triacylglycerol structure constitute an important factor governing the atherogenic character of a fat or oil (1). A study by Kritchevsky et al. (2) involving different fats containing 24% palmitic acid indicated that for rabbits, lard was significantly more atherogenic than tallow. Lard contains about 90% of its palmitic acid residues at the sn-2 position of the glycerol backbone. By contrast, in tallow less than 15% of the palmitic acid residues are present at the sn-2 position. Moreover, both physical properties (3) and oxidative stability (4) are significantly influenced by the identities and positions of the fatty acid residues on the glycerol backbone.The fatty acid composition of triacylglycerols is usually elucidated by gas chromatography (GC), as are regio-and stereoselective analyses subsequent to a partial hydrolysis process and several purification steps. Mattson and Lutton (5) have suggested the use of a 1,3-specific lipase (pig pancreatic lipase) to carry out a partial digestion of a triacylglycerol sample, followed by purification of the mixture of sn-2 monoacylglycerols produced by the digestion. The fatty acid composition of this mixture of sn-2 monoacylglycerols is determined via GC. Brockerhoff (6) has reported a stereospecific analysis of triacylglycerols which utilizes a pancreatic lipase or Grignard reagent (7) to effect partial deacylation of the triacylglycerol. This reaction generates mixtures of sn-2 monoacylglycerols and sn-1,2 and sn-2,3 diacylglycerols when an sn-1,3-specific lipas...
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