ABSTRACT
Production of vegetable oil exceeds 75 million metric tons (1996/1997) valued in excess of US$38 billion (U.S. Department of Agriculture, WASDE-345 and Oil Crops Update 1998). The majority of vegetable oils in common use are composed primarily of four fatty acids: palmitic (16:0), oleic (18:1∆9), linoleic (18:2ω6,9), and linolenic (18:3ω3,6,9). However, these fatty acids represent only a small fraction of the diverse structures of fatty acids produced by plants. When considering the known alterations in chain length, double-bond position, and number as well as oxygenated functional groups, the number of described plant fatty acids exceeds 200 [1,2]. If available at the low costs of current commodity vegetable oils, many of the less common fatty acid structures may have attractive applications as industrial feedstocks, polymer precursors, and other petrochemical replacements. Through gene transfers, the opportunity exists for a wide range of alterations in fatty acid biosynthesis in traditional oilseed crops. Certainly, oilseed lipid metabolism provides one of the best models for the cellular biochemistry involved in producing high-value products in plants. However, for metabolic engineering to be feasible and attractive, at least two prerequisites must be met. First, detailed information must be available (both biochemical and genetic) about the pathway(s) of interest and, second, the potential for economic returns of investments must exist. Hitz recently presented an excellent example of cost analysis used in evaluating the potential of transgenic crops [3]. In at least a few cases, metabolic engineering of oilseed lipid biosynthesis satisfies both criteria.
