Novel products produced from seed oil materials (TAG, phospholipids, and minor components such as tocopherols, sterols, stanols, and fatty acyl esters of the latter two) by enzyme-mediated purification or chemical modification are reviewed. The primary focus is on "value-added products" of current and potential use (particularly in the food, cosmetics, and pharmaceutical industries) that require the selectivity of enzymes and mild operating conditions, the latter being beneficial for polyunsaturated and oxygenated acyl groups. The paper briefly reviews the biochemistry of enzymes in lipid modification (lipases, phospholipases, and lipoxygenases) and discusses and assesses the current and future applications, current state of the art, and areas for future research for the following enzyme-mediated processes: isolation of polyunsaturated and oxygenated FFA; formation of structured TAG as nutraceuticals; formation of MAG, saccharide-FA esters, and other polyhydric alcohol ester as emulsifiers and surfactants; isolation and/or modification of tocopherols and sterols as antioxidants; formation of hydroperoxides as chemical intermediates; and modification of phospholipids for use in liposomes.Agriculturally derived feedstocks will play an increasingly important role in North America and worldwide as the cost of petroleum continues to increase and its availability decreases. Lipids (TAG, phospholipids, sterols, etc.) are an example of such a feedstock. Although lipids are readily modified by chemical means (reviewed in Refs. 1-5) and can be synthesized from petroleum-based feedstocks (6), there is an increased interest in modifying lipids via biocatalysis, particularly to manufacture lipid-based products in the food, cosmetics, and pharmaceutical industries, and for applications focused on environmental friendliness, due to the mild reaction conditions and narrow product distributions. In addition, biocatalysis has also played a role in isolating natural products, for instance, by temporarily modifying the molecule of interest to facilitate downstream separations. Reviews on biocatalytic modification of lipids have appeared during the last 15 yr (7-11) and more recently in two monographs (12,13). In addition, a recent conference entitled Enzymes in Lipid Modification was held in 2003 in Greifswald, Germany (14). The organization and emphasis of the previous reviews focused mostly on the types of biocatalysts; the emphasis here is on the products formed. Preceding the discussion of products is a brief overview of the important biocatalytic tools to be used.
BIOCATALYSTS USED FOR LIPID MODIFICATIONLipases (EC 3.1.1.3). Lipases are specifically designed by nature for the hydrolysis and synthesis of ester bonds involving FA, and can form and/or hydrolyze amide, carbonate, and thioester bonds as well. Reactions catalyzed by lipases that involve the ester bond are diagrammed in Figure 1. Lipases are perhaps the most frequently used enzymes for biotransformations because of their ability to function in nonaqueous and aqueous ...