Esterification interesterification

Lipases are subclass of esterases, capable of hydrol3 ing esters, fats and lipids in aqueous media, hence they are described as hydrolases belonging to class EC 3.1.1.3. Lipases are one of the most versatile enzymes because they can catalyze many different reactions such as esterification, interesterification, hydrolysis, alcoholysis, peroxidation, aminolysis, and epox-idation. " " Most lipases have similarities in their amino acid sequence including within the catalytic region, His-X-Y-Gly-Z-Ser-W-Gly or Y-Gly-His-Ser-W-Gly where W, X, Y and Z refer to unspecified amino acid residues. These enzymes are stereospecific towards ester bonds thereby eliminating any undesirable by-products of the reaction. Lipase has been used extensively as a biocatalyst in industry because of its high thermal stability, versatile pH range and it can be used repeatedly if immobilized e.g. Novozyme 435). ... 

Yoon, S. H. Nakaya, H. Ito, O. Miyawaki, O. Park, K. H. Nakamura, K. Effects of Substrate Solubility in Interesterification with Riolein by Immobilized Lipase in Supercritical Carbon Dioxide. Biosci. Biotechnol. Biochem. 1998, 62, 170-172. Yu, Z. R. Rizvi, S. S. H. Zollweg, J. A. Enzymatic Esterification of Fatty Acid Mixtures from Milk Fat and Anhydrous Milk Fat with Canola Oil in Supercritical Carbon Dioxide. Biotechnol. Prog. 1992, 8, 508-513. 

Rousseau et al. (1996a, b) examined the properties of physical blends and those of blends obtained on chemical esterification of milk fat-canola oil blends (using 0.5% methoxide, 78-82°C for 15-120 min). For milk fat-canola oil blends containing >20%, w/w, canola oil, chemical interesterification reduced the solid fat content of all blends (Rousseau et al., 1996a). For non-interesterilied and interesterified blends, hardness decreased with increasing content of canola oil. 

From Bookish, M., Fats and Oils Handbook, AOCS Press, Champaign, IL, 1998, with permission. bFrom Sonntag, N. V, Fat Splitting, Esterification, and Interesterification, in Bailey s Industrial Oil and Fat Products, 4th ed Vol. 2., D. Swem, Ed., pp. 97-173, John Wiley Sons, New York, 1982. With permission. cn = native r = randomized. 

Enzymatic reactions in organic media have been a major issue in the field of biocatalysis over the last two decades. Carboxylesterases (mostly lipases) have been used in monophasic organic solution under controlled values of water activity (ajj for catalyzing ester formation the reaction equilibrium can be shifted towards ester formation by interesterification or transesterification [1]. Direct esterification is often hampered by water formation, which may increase o , thus negatively influencing the equihbrium. 

Under almost anhydrous conditions in organic medium, lipases can be used in the reverse mode for direct ester synthesis from carboxylic acids and alcohols, as well as transesterifications (acyl transfer reactions) which can be divided into alcoholysis (ester and alcohol), acidolysis (ester and acid), and interesterification (ester-ester interchange). The direct esterification and alcoholysis in particular have been most frequently used in asymmetric transformations involving lipases. The parameters that influence enzymatic catalysis in organic solvents have been intensively studied and discussed. ... 

The term interesterification is often used to describe reactions that involve the exchange of acyl residues between an ester and an acid (acidolysis), an ester and an alcohol (alcoholysis), or an ester with another ester (rranj -esterification). 

N. O. V. Sonntag, Fat Splitting, Esterification, and Interesterification, Bailey s Industrial Oils and Fats, 4th ed., Wiley, New York. 

It is also possible to shift the equilibrium of the reaction by removing the formed reaction products (according to the Le Chatelier s principle) (162). For example, the ability to remove water in continuous esterification reactions in SCCO2 has been cited as one of the advantages of using SCCO2 versus traditional solvents, such as hexane (163). In their study on the interesterification of tricaprylin and methyl oleate in SCCO2, Adschiri et al. (164) concluded that the selective extraction of the reaction product, methyl caprylate shifted the equilibrium of the reaction forward. 

Structured lipids (SLs) are defined as TAGs restructured or modified to change their FA composition or their positional distribution in TAG molecules by chemical or enzymatic reaction, such as direct esterification, acidolysis, alcoholysis, or interesterification, depending on the types of substrates available (Lee and Akoh, 1998). 

Isono, Y, Nabetani, H., and Nakajima, M., Lipase-surfactant complex as catalyst of interesterification and esterification in organic media, J. Ferment. Bioeng., 80, 170-175, 1995. 

Lipases (triacylglycerol hydrolases, EC 3.1.1.3) are enzymes that catalyze reactions such as hydrolysis, interesterification, esterification, alcoholysis, acidolysis, and aminolysis [1]. There is an increasing interest in the development of lipase applications to oleochemical transformations to obtain esters of long-chain fatty acids, as monoalkyl esters of fatty acids [2]. Utilization of lipase as a catalyst for the production of biodiesel, defined as a mixture of monoalkyl esters, is a clean technology due to its nontoxic and environmental fnendly nature, requiring mild operating conditions compared with chemical method [3]. 

Interesterification is an interchange of acyl groups between either ester and alcohol (alcoholysis), ester and acid (acidolysis), or between two esters (proper esterification). Esterification is most widely applied to fat modification because it relocates FA in TAG of one or several fat components to be modified, hi this process, acyl groups are repositioned both within TAG molecules (intramolecular esterification) and between different molecules (intermolecular esterification). 

Structured lipids (SL) are TAG that contain combinations of short-chain fatty acids (SCFA), medium-chain fatty acids (MCFA), and long-chain fatty acids (LCFA) located in the same glycerol molecule these may be produced by chemical or enzymatic processes (29,30). These specialty lipids may be produced via direct esterification, acidolysis, and hydrolysis or interesterification. Structured lipids are developed to fully optimize the benefits of their fatty acid varieties in order to affect metabolic parameters such as immune function, nitrogen balance, and lipid clearance from the bloodstream. 

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