Plants as industrial chemical factories - new oils from genetically engineered soybeans

Abstract

The major uses of soybean oils world-wide are for food products such as frying oils, shortenings and margarine. Refined soybean oil is usually chemically hydrogenated to increase storage life, stability during frying, and to increase its melting point for use in solid fat applications. Hydrogenation results in the formation of monounsaturated trans fatty acids, the consumption of which has been associated with an increased risk of coronary heart disease in humans. It is nutritionally desirable, therefore, to produce trans-free soybean oils rich in monounsaturated fatty acids for cooking and trans-free oils rich in stearic and oleic acids for shortenings and margarine. Cloned genes may be introduced into soybeans to create transgenic lines with improved oil traits. The design of transgene constructs has been assisted by the use of soybean somatic embryos in suspension culture as a model system for soybean seed transformation. This system has allowed the selection of the right genes and promoters to achieve the desired phenotypes in transgenic soybeans. By manipulating the expression of fatty acid desaturase genes we have produced lines with 85% oleic acid in their seed oil and lines with up to 30% stearic acid. Commercialization of high-oleic acid transgenic soybeans has demonstrated that it is possible to drastically alter the fatty acid composition of a soybean seed without affecting the yield or environmental sensitivity of the soybean plant. We have demonstrated that high-oleic soybean oil is also useful for non-food applications such as biodegradable lubricants. We have now cloned a number of fatty acid desaturase-related genes from species which produce unusual and industrially useful fatty acids. By expressing these genes it will be possible to produce new fatty acids in soybean seeds, which could potentially replace petrochemicals as raw material for many industrial processes.