Lipases are quite useful for synthesizing structured lipids (SLs) which are triacylglycerols (TGs) having particular fatty acid (FA) residues at specific positions. In regard to the number of FA species and their distribution in the glycerol molecule, TGs may be classified as; AAA-, ABA-, AAB-, and ABC-types. AAA-type TGs can be synthesized from FA and glycerol either chemically or enzymatically. Even with a stoichiometric mixture of substrates, nearly complete synthesis is possible. The syntheses of other types of TGs require positionally specific reactions, for which regio-specifc lipases are useful. ABA-type SLs are synthesized by either 1) 1, 3-position-specific lipase-catalyzed acyl exchange of TG with FA or with FA ethylester (FAEt); or 2) 1, 3-position specific lipase-catalyzed acy-lation of glycerol with FA, giving symmetric 1, 3-diacyl-sn-glycerol. Subsequent to chemical acylation at the sn-2 position; or 3) 1, 3-position-specific lipase-catalyzed deacylation of TG gives 2-monoacylglycerol, which then undergoes reacylation at 1 and 3 positions with FA or FA ethylester. AAB-type SL is obtained by lipase-catalyzed mono-substitution at the 1 or 3 position of AAA-type TG with FA or FAEt, thus avoiding formation of any di-substituted by-product. Stereopreference to sn-1 position over sn-3 position of a certain lipase makes possible the syntheses of chiral AAB-and ABC-type TGs.

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Brassica napus with canola quality represents a major source of energy for both humans and livestock. Since its inception, the value of canola has continued to improve through the development of varieties with desirable traits such as higher oil content, improved fatty acid profile and reduced antinutritional factors such as fiber. Biotechnology approaches, including microspore culture, embryo rescue and molecular markers have offered a wide spectrum of methods for developing superior breeding lines. The incorporation of novel traits has led to the development of stable hybrid systems and herbicide tolerant varieties. Use of the half-seed selection method has facilitated the identification of lines with modified fatty acid profiles, including higher oleic, lower linolenic and lower saturate canolas. The challenge that the industry faces is to keep pace with the constant evaluations by nutritionists as well as changing demands of the consumer and the food industry.

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Study on microbial lipid production was started at the beginning of the 20^th century. In 1985 the first industrial production of microbial lipid containing γ-linolenic acid was carried out. Microbial lipids containing arachidonic acid and docosahexaenoic acid were subsequently produced. These lipids are polyunsaturated fatty acids (PUFAs), or essential fatty acids for human. PUFA is the most important object in the research of single cell oil, a substitutive term of microbial lipid. As PUFA composition in microorganisms depends on their genera to some extent, PUFA can be chemotaxonomically used as an index matter of their classification. In the present review on lipid and PUFA production, especially γ-linolenic acid, arachidonic acid and docosahexaenoic acid by yeasts, fungi and labyrinthulae are discussed, with attention to the differences in batch and continuous cultures. How microbial lipids come to be produced on an industrial scale is explained.

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Lipase (triacylglycerol acylhydolase) hydrolyzes ester bonds between glycerol and fatty acid of triacylglycerol. Interesterification and ester synthesis by immobilized lipase is carried out in the oils and fats industry.
Basic characteristics of commercially available immobilized (with anion-exchange regin) 1, 3-specific lipase from Rizomucor miehei (Lipozyme RM IM) were investigated and found to be influenced by water contents, reaction temperature, reaction mixture organic solvents differences in alcohol (chain length and primary/secondary) as substrate and carrier particle size. Heat stability of immobilized lipase increased significantly and halflife-time in the column was 1600 hrs.
Candida antarctica lipase B was immobilized with a less expensive silica based carrier. The performance of ester synthesis was compared with a commercial product immobilized with macroporous acrylic resin (Novozyme 435). The ester synthesis of 4 industrially important materials has been conducted and of these, the silica based immobilized material showed the poorest performance. The selection of carrier is thus important.
An 1, 3-specific lipase of Thermomyces lanuginosus produced by genetically modified microorganism with very high enzyme yield was immobilized with the silica based material and its performance for margarine interesterification was assessed. Due to 1, 3 specificity, more fatty acid at 2nd-position of original fat was noted to remain at the same position in contrast to chemical method. The solid fat content was essentially the same for the products produced by the two methods, thus indicating that the enzymatic method alone can be used.
Features of immobilized lipases are presented.

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Lipases are among the most important enzymes in the oil and fats industry. Large quantities of microbial lipases are being produced on an industrial scale for medical and industrial uses.
The high selectivity and specificity of lipases make them useful for obtaining structured lipids. For example, synthesis of cocoa butter substitutes, human milk fat substitutes, position-specific low-calorie lipids and modified lipids that incorporate eicosapentaenoic and docosahexaenoic acids has been reported.
Lipases usually lose activity during the course of continuous reaction and are costly. Factors that influence the activity of lipases are water activity, temperature and oil refine. Several methods were carried out to improve lipase stability. These methods may involve addition, chemical modification, genetic engineering and reaction condition.

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