Food Lipids: Chemistry, Nutrition, and Biotechnology

existing genes in the host plant genome, thus decreasing enzyme activities and enzymatic
products that are not desired.
All these facets of adding genes can be used to redirect the molecular pathway
by which oils are synthesized in plants; since these changes are determined by the
genes, the changed oil in a transgenic plant will also be seen in the progeny of that
plant. Thus, new crop species can be created that essentially look the same as the
parent crop, yet produce a significantly different oil. A transgenic soybean plant looks
like any other soybean plant and can be grown by the farmer in exactly the same
ways.
A review of the detailed methods used to genetically engineer oilseed crops is
outside the scope of this chapter. The reader is referred to several reviews (1,3,4).
The intent of this summary is to describe some of the practical impacts on the food
lipids area that will result from the introduction of a set of technologies that lead to
new crop varieties, which in turn produce new raw materials for the food industry.
III. THE EXAMPLE OF LAURATE CANOLA
Coconut and oil palm kernel are the primary sources of lauric oils. Both are produced
from trees grown in the tropical zone, and each contains about 50% lauric acid by
weight. However, some temperate zone plants (e.g., Cuphea glutinosa, Umbellularia
californica) accumulate even higher levels of lauric acid in seed oils. Therefore, a
priori, it appeared in the early 1980s that lauric acid oils could conceivably be
produced in temperate zone agricultural systems. For industries in the United Sates,
a temperate zone crop source of lauric acid would (a) help address national import/
export imbalances; (b) perhaps stabilize world price fluctuations for lauric acid oils;
and (c) conceivably provide an oil with higher lauric acid content and the associated
savings in processing costs.
When Calgene, Inc., of Davis, California, initiated a project in 1985 to engineer
Brassica napus canola into a lauric oil producer, there was a long list of technical
unknowns. There was no reliable system for putting genes into canola and getting
back normal plants. The available data suggested that a gene from a monocotyledonous
plant like coconut might not function correctly when transferred to a dicotyledonous
plant like canola. The general opinion was that production of lauric acid
in nonseed tissues might be detrimental or even lethal to a canola plant. Indeed, even
as late as 1990, it was thought that lauric acid might ‘‘gum up’’ triacylglycerol
synthesis in canola. Certainly in 1985 there was an insufficient understanding of how
to limit foreign gene expression to just the developing seed of a transgenic canola
plant. Also there was absolutely no experience, on which to base assumptions that
a transgenic oil or simply the process of generating transgenic canola would not
somehow compromise the agronomic productivity of canola. The perhaps most worrisome
aspect of all was that no one knew, despite numerous tries, the mechanistic
basis of laurate accumulation in coconut or oil palm kernel, let alone the wild species
of Cuphea glutinosa or Umbellularia californica.
This list of technical challenges provides a framework to understand the steps
and areas of technical expertise required to generate a useful new crop type containing
a genetically engineered oil.
In the example of lauric acid canola, scientists were able to demonstrate the
existence of a unique enzyme comprising lauroyl-acyl carrier protein (ACP) thio-
Copyright 2002 by Marcel Dekker, Inc. All Rights Reserved.