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Food Lipids: Chemistry, Nutrition, and Biotechnology

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Figure 8 Reaction scheme showing acidolysis reaction in the synthesis of structured lipids<br />

from caprylic acid <strong>and</strong> triolein (62).<br />

lipase<br />

MCT � LCT ⎯→ SL<br />

lipase<br />

LCT � MCFAEE ⎯→ SL � LCFAEE<br />

lipase<br />

MCT � LCFAEE ⎯→ SL � MCFAEE<br />

where MCFAEE = medium chain fatty acid ethyl ester <strong>and</strong> LCFAEE = long chain<br />

fatty acid ethyl ester. This method is widely used in lipid modifications <strong>and</strong> in the<br />

synthesis of SLs (4,47,64,65).<br />

In a transesterification reaction, generally, hydrolysis precedes esterification. In<br />

all the preceding examples, short chain triacylglycerols (SCTs) or short chain fatty<br />

acids (SCFAs) can replace MCTs <strong>and</strong> MCFAs, respectively, or can be used in combination.<br />

Figures 9 <strong>and</strong> 10 give examples of the suggested strategies involving interchange<br />

reactions between a TAG (trilinolein) <strong>and</strong> a TAG (tricaproin) ester <strong>and</strong><br />

between EPA ethyl ester <strong>and</strong> tricaprin, respectively. We have successfully used enzymes<br />

to synthesize position-specific SLs containing n-3 PUFAs with ability to improve<br />

immune function <strong>and</strong> reduce serum cholesterol (31,32).<br />

e. Factors That Affect Enzymatic Process <strong>and</strong> Product Yield<br />

Water. It is generally accepted that water is essential for enzymatic catalysis.<br />

This status is attributed to the role water plays in all noncovalent interactions. Water<br />

is responsible for maintaining the active conformation of proteins, facilitating reagent<br />

diffusion, <strong>and</strong> maintaining enzyme dynamics (66). Zaks <strong>and</strong> Klibanov (67) reported<br />

that for enzymes <strong>and</strong> solvents, tested enzymatic activity greatly increased with an<br />

increase in the water content of the solvent. The absolute amount of water required<br />

for catalysis for different enzymes varies significantly from one solvent to another<br />

(56). Hydration levels corresponding to one monolayer of water can yield active<br />

enzymes (68). Although many enzymes are active in a variety of organic solvents,<br />

the best nonaqueous reaction media for enzymatic reactions are hydrophobic, waterimmiscible<br />

solvents (67,69,70). Enzymes in these solvents tend to keep the layer of<br />

essential water, which allows them to maintain their native configuration, <strong>and</strong> therefore<br />

catalytic activity.<br />

Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.

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