hapter 9 Biotransformation of lipids 9.1 Introduction In this chapter we will examine how cells and enzymes are used in the transformation molecular of lipids. The lipids are, of course, a very diverse and complex series of molecular alcohols, waxes, terpenes and steroids. It is usual to teach about these molecules, in a iochemical context, in more or less the order given above, since this represents a logical sequence leading from simple molecules to the more complex. Here, however, we have dopted a different strategy. Clearly, the technical and commercial aspects of industrial lipid transformation are both diverse and complex. We have, therefore, to be selective in what we can include in a ingle chapter. We have decided to begin the chapter by discussing the transformation of sterols and steroids since these transformations are illustrative of the potency of biocatalysts in bringing about selective and stereospecific chemical transformation of uite complex molecules. This part of this chapter is a logical extension of the issues iscussed in the previous chapter. We have also elected to focus on the technical rather than the commercial issues although attention is drawn to the importance of commercial criteria in the selection of strategies for production. The reader should be aware, however, that the production of steroids for pharmaceutical use and as contraceptives is a large market. Estimates of annual sales of these materials vary widely(WHO 1990 Year Book $3x10 annum"-$10 annum" )reflecting the difficulty of accessing details on such a diverse group of compounds After discussing the biological capability to transform steroids, we briefly examine the biotransformation of other terpenoids to ensure that the reader develops an awareness of the potential of biotechnology to modify or produce derivatives of a wide range of natural materials that are of tremendous potential, commercial value in the food and health care sectors. We also include a brief consideration of the use of biocatalysts to transform a range of other hydrocarbon compound The bulk of the chapter is therefore concerned with highly specific reactions arising to produce molecules of known structure. However, in a chapter on lipid transformation, we should not miss the use of general lipases to change the composition of triglycerides Although the replacement of one set of fatty acids in trig ycerides is, from a chemical/biochemical point of view, not as stimulating as the biotransformation of steroids, it is of major commercial value in the food industry. The biotransformation of triglycerides (and phospholipids) to produce food materials which have desirable organoleptic properties(eg melt in the mouth feel)potentially dwarfs the steroid market in terms of volume and turnover The placing of this topic towards the end of the chapter does not imply that it is of limited commercial value The final part of the chapter briefly explores the potential of using non-aqueous solve for lipid transformation294 Chapter 9 Biotransformation of lipids 9.1 Introduction In this chapter we will examine how cells and enzymes are used in the transformation of lipids. The lipids are, of course, a very diverse and complex series of molecular entities including fatty acids, triglycerides, phospholipids, glycolipids, aliphatic alcohols, waxes, terpenes and steroids. It is usual to teach about these molecules, in a biochemical context, in more or less the order given above, since this represents a logical sequence leading from simple molecules to the more complex. Here, however, we have adopted a different strategy. Clearly, the technical and commercial aspects of industrial lipid transformation are both diverse and complex. We have, therefore, to be selective in what we can include in a single chapter. We have decided to begn the chapter by discussing the transformation of sterols and steroids since these transformations are illustrative of the potency of biocatalysts in bringing about selective and stereospecific chemical transformation of quite complex molecules. This part of this chapter is a logical extension of the issues discussed in the previous chapter. We have also elected to focus on the technical rather than the commercial issues although attention is drawn to the importance of commercial criteria in the selection of strategies for production. The reader should be aware, however, that the production of steroids for pharmaceutical use and as contraceptives is a large market. Estimates of annual sales of these materials vary widely (WHO 1990 Year Ekmk $3~10' annum-' - $10'' annum-') reflecting the difficulty of accessing details on such a diverse group of compounds. After discussing the biological capability to transform steroids, we briefly examine the biotransformation of other terpenoids to ensure that the reader develops an awareness of the potential of biotechnology to modify or produce derivatives of a wide range of natural materials that are of tremendous potential, commercial value in the food and health care sectors. We also include a brief consideration of the use of biocatalysts to transform a range of other hydrocarbon compounds. The bulk of the chapter is therefore concerned with highly speafic reactions arising to produce molecules of known structure. However, in a chapter on lipid transformation, we should not miss the use of general lipases to change the composition of triglycerides. Although the replacement of one set of fatty acids in trigycerides is, from a chemical/biochemical point of view, not as stimulating as the biotransformation of steroids, it is of mapr commercial value in the food industry. The biotransformation of triglycerides (and phospholipids) to produce food materials which have desirable organoleptic properties (eg melt in the mouth feel) potentially dwarfs the steroid market in terms of volume and turnover. The placing of this topic towards the end of the chapter does not imply that it is of limited commercial value. The final part of the chapter briefly explores the potential of using non-aqueous solvents for lipid transformation. bids i~~~ea wide^$^^! types