APPLICATION OF PLANT BIOTECHNOLOGY FOR PRODUCTION OF QUALITY OILS

Fats and Oils differ only in that fats are solids and oils are liquid at room temperature.
Fats & Oils that occur in plants and animals consist of mixtures if triacylglycerol s (also referred to as triglycerides).
These non-polar, water-insoluble substances are fatty acid tri-esters of glycerol
Their fatty acid composition vary with the organism that produce them.
Plant oils are usually richer in unsaturated fatty acids than are animal fats.
Fatty acids are carboxilic acids with long chain hydrocarbons side groups.
Unsaturated fatty acids contain one or more double bonds between carbon atoms. In saturated fatty acids all of the carbon atoms are bonded to the max. number of hydrogen atoms.

Some biological fatty acids

Saturated fatty acids
Lauric acid 12:0
Palmitic acid 16:0
Stearic acid 18:0
Arachdonic acid 20:0

Unsaturated fatty acids
Palmitoic acid 16:1
Oleic acid 18:1
Linoleic acid 18:2
α – linolenic acid 18:3
γ- linolenic acid 18:3
Arachidonic acid 20:4

Plant species use different polymers generally oil & starch, to store energy required for seedling growth. The oil may be present in seeds (e.g. ground nut, mustard, rapeseed, sunflower & soya bean which contain upto 50% of the seed dry weight) or fruits (e. g. olive, ovocado and oil palm fruits which contain high level of oils)
Vegetable oil is a major commodity for both food & industrial needs.
The fatty acid composition of the oil used for food or industrial applications differ.
Oil quality(fatty acid composition) & yield can be improved by genetic engineering to suit our needs. An example for such kind of genetic modification is the high lauric acid ( a fatty acid with 12 carbon atoms ) rape seed (canola) oil.
The wild type rape seed contain 60% oleic acid with other fatty acids.
The genetically engineered rapeseed plant variety (laurical) produced lauric acid a 12 carbon fatty acid used to make soaps and detergents.
The researchers introduced only one gene coding for a thioesterase enzyme from the California bay tree which contain high levels of lauric acid.
The shut off fatty acid synthesis after 12 carbons rather than allowing the acid to grow to 18 carbon length (oleic acid) normal for the plant while having little effect on the productivity.
There was a dramatic change in the spectrum of fatty acids in the oil i.e. a change from 60% oleic acid to 60% lauric acid. The genetically engineered oil is already in commercial production.
Mono unsaturated fatty acid level in plants is desirable so that the net value of oils is enhanced. The transgenic soyabean with modified oil composition from about 25% oleic acid to over 85% has been developed and this improved oil has important food and non-food uses.
Rape seed is poor in stearate & stearic acid. An antisense DNA was constructed for the critical enzyme and introduced into embryos of rape sedd.
The transgenic rape seed oil with high level of stearate was produced and is used in the manufacture of margarine (a butter like solid oil)
A ∆15 desaturase gene was introduced into rape seed. The transgenic plant produced oil rich in α – linolenic acid.
The gene for the biosynthesis of oil in cocoa was transferred to soya through disarmed Ti plasmid. The transgenic soya bean produced cocoa oil that can be used for chocolate making.
γ- linolenic acid (GLA) is the first intermediate in the bioconversion of linoleneic acid to arachidonic acid.
GLA is important in alleviating hyper cholesteromia and many caronary heart diseases.
It is not produced in oil seed crops.
This conversion is catalysed by by ∆6 desaturase, and the gene encoding this enzyme has been cloned from the cyanobacterium synechocystis.
Expression of this gene in transgenic tobacco resulted in the production of GLA.
In 1998, this desaturation gene has been cloned from filamentous fungi, moteirella alpina and transferred to canola.
The hydroxy fatty acid vicinoleic acid has industrial applications in the manufacture of nylon paints, varnishes, resins, lubricants, and cosmetics.
Transgenic arabidopsis expressing castor oleate hydroxylase gene accumulated ricinoleic acid upto 17% of the total lipid fraction
Somerville & coworkers of michigan state university have cloned the arabidopsis gene which codes for an enzyme that catalyses the synthesis of polyunsaturated fatty acids
Dietary poly unsatured fatty acuds have a role in lowering bloof cholesterol and are needed for human growth.
Since then the eight different desaturase genes from arabidopsis that control the polymerisation of plant oils have been isolated.
These genes have been inserted into plants such as soyabean, canola & flax that typically make more saturated oils
This resulted in the production of nutritionally improved oils in the crops
Thus it is possible to tailor plant oils to specific nutritional needs.