Biomedical Engineering Reference
In-Depth Information
Type of oil
Low linolenic soybean
High oleic sunflower
Regular sunflower
Regular soybean
FIGURE 10.3 Comparison of fatty acids in regular sunflower and soybean vs. genetically
engineered crops. (Adapted from Skillicorn. 53 )
been blamed for its relatively poor oxidative stability compared with corn, cotton,
and sunflower oils. This is particularly important in frying, where oil flavor, odor,
and color deteriorate with prolonged exposure to air at high temperatures. 53
To reduce the level of polyunsaturated fatty acids, the genes for the enzymes
that desaturate oleic acid to make linoleic acid (
12-desaturase) and desaturate
linoleic acid to make linolenic acid (
, 15-desaturase) have been cloned from both
soybean and canola. Fader et al. 55 evaluated the co-suppression in soybean and
canola. They used a DNA coding for the two desaturase enzymes (oriented in the
sense direction), which were joined with seed-specific promoters and placed into
vectors suitable for transformation. For soybean an embryonic axis tissue which was
transformed using gene gun technology was used. For canola, an Agrobacterium
tumefaciens -based system was used to transform hypocotyl tissue of the cultivar
Westar. Soybean lines containing co-suppressed
12-desaturase were identified
with linoleic acid levels less than 3% and oleic acid levels over 76%. In canola, co-
12-desaturase lines were selected that had oleic acid levels of 83%
and linoleic acid levels near 6%.
Designing a Special Fatty Acids Composition
Control of the degree of unsaturation has been directed to change the oil composition
of a crop like sunflower from high linoleic acid to oleic acid. This can change the
value of the oil, both from the point of view of food usage and for industrial purposes,
because the presence of high purity oleic acid increases the possiblities for derivation
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