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in this article we will discuss about the production of medium and longer chain fatty acids.
Productions of Medium Chain Fatty Acids:
Several plant oil is made up of medium chain or short chain fatty acids. Major portion of the vegetable oil consist of fatty acids like stearic, palmetic, oleic, linoleic and linolenic acids. These are C16 and C18 in length. Short chain fatty acids such as lauric acid (12: 0) are extensively used to make detergent and soaps.
One of the main sources for lauric acid is tropical coconut oil and palm kernal California bay (Umbellularia californica) grows in the region of northern California. Team of scientist from California based Calgene company transferred high producing character from California bay into temperate oil crop such as oil seed rape (Brassica).
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Generally length of each fatty acid is controlled by an enzyme thioesterase which cleaves fatty acid from carrier protein (ACP). Thus a plant that synthesise fats that have primarily C12 fatty acid has a very active C12 thiosterase (Fig. 17.3). Thus it can be presumed that California bay seeds with C12 fatty acid have very active C12 thioesterase.
The gene for C12 thioesterase was introduced in to the oil seed rape with seed specific napin promoter (Fig. 17.4). As a result of successful cloning of foreign gene causes fatty acid synthesis to terminate at 12: 0 stage and the seeds made oil with C12 lauric acid of about 25% along with their native normal C18 fatty acid (75%).
Production of Longer Chain Fatty Acids for Industrial Use:
Plant oil containing fatty acids longer than C18 are desirable for industrial use. Oil rape seed and many brassica species contains long chain fatty acid known as erucic acid. Synthesis of erucic acid is carried out by two step elongation process in which oleoyl-CoA (18: ∆9) is converted to erucoyl-CoA (22: ∆13) by an enzyme elongase. Although erucic acid has potential for industrial use. It is however, unsuitable for edible purpose. Attempts are being made to over express elongase gene in transgenic plants in order to produce high level of industrially important erucic acid.
