Omega-3 (n-3) long-chain polyunsaturated fatty acids (LC-PUFA) are essential or conditionally essential dietary nutrients for vertebrates with well-established health benefits in humans.
Specifically, n-3 LC-PUFA including eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3) have key roles in neural development, immune and inflammatory responses, and beneficial effects in several pathological conditions, including cardiovascular and neurological diseases, and some cancers.
The International Society for the Study of Fatty Acids and Lipids recommends a daily intake of 500?mg of n-3 LC-PUFA (EPA + DHA) for optimum cardiovascular health and, projecting this to a population of 7 billion, this amounts to a total annual requirement for over 1.25 million metric tonnes (mt) of n-3 LC-PUFA. The annual global supply of fish and fish oil cannot meet this level of requirement for n-3 LC-PUFA and so there is a large gap between supply and demand.
Microalgae in the marine and aquatic environments are the primary producers of the vast majority of n-3 LC-PUFA, which accumulate in the marine food web and thus fish and seafood are the predominant source of these essential nutrients in the diet.
However, global fisheries are at, or beyond, exploitable limits and cannot increase to satisfy the growing demand for fish and seafood and, therefore, around 50% is now farmed.
Paradoxically, high levels of n-3 LC-PUFA in farmed fish and shrimp was only assured by the use of fishmeal and, especially, fish oil, themselves finite and limited marine resources derived from wild fisheries.
The only biological alternatives to fish oil, vegetable oils, do not contain n-3 LC-PUFA as this biosynthetic pathway is not present in terrestrial plants. Therefore, as demand for fish and seafood increases, so will that of n-3 LC-PUFA and, as supplies are finite10, the gap between the two will only continue to increase in the future.
The only sustainable solution to the ever-increasing global demand for n-3 LC-PUFA is de novo production of entirely new sources. This requires the application of modern biotechnology ranging from genetic modification through to synthetic biology to introduce the n-3 LC-PUFA biosynthesis trait into appropriate oleaginous platforms.
This has been applied to produce EPA in the yeast Yarrowia lipolytica, and DHA in the diatom Phaeodactylum tricornutum that normally produces only EPA. However, oilseed crops dominate world oil production and there is a highly organised and well-established infrastructure for the cultivation, harvest, processing, distribution, marketing and utilisation of vegetable oils.
Therefore, a highly practical approach to developing a novel, renewable supply of n-3 LC-PUFA is the metabolic engineering of oilseed crops with the capacity to synthesize these bioactive fatty acids in seeds. Production of EPA and DHA in seeds was initially demonstrated in the model plant Arabidopsis, and was recently reported in an oilseed crop, Camelina sativa. C. sativa or false flax, is a member of the Brassicaceae family and an ancient oilcrop that in the wild type produces an oil with up to 45% of fatty acids as α-linolenic acid (LNA; 18:3n-3).
In the present study, C. sativa was transformed with a suite of five microalgal genes to produce a higher plant source of n-3 LC-PUFA30. The extracted seed oil, containing 20% of total fatty acids as EPA, was investigated as a replacement for marine fish oil in feeds for Atlantic salmon (Salmo salar).
Triplicate groups of salmon were fed one of three experimental diets containing fish oil (FO), wild-type Camelina oil (WCO) or EPA-Camelina oil (ECO) as the sole added lipid source for 7-weeks. The results showed that growth performance, feed efficiency, fish health and nutritional quality in terms of EPA + DHA for the human consumer were all unaffected by replacing FO with ECO.
Metabolic analysis confirmed the EPA to DHA pathway was active in liver and transcriptomic analysis indicated that the EPA:DHA ratio had greater influence on gene expression than absolute level of EPA.
This translational research has demonstrated that n-3-LC-PUFA enriched oils from transgenic oilseed crops can be effective substitutes for fish oil in feeds for Atlantic salmon, capable of maintaining n-3 LC-PUFA levels in farmed fish. Thus, oils extracted from modified oilseed crops represent a potential solution to supplying the growing demand for these critically important dietary nutrients.
Read a summary of the article: http://www.thefishsite.com/fishnews/25015/oil-from-gm-camelina-can-substitute-fish-oil-in-fish-feed
March 2015
